This superclass contains two living classes: Myxini, the hagfishes, and Cephalaspidomorphi, the lampreys. Each class consists of one living order and one living family. There are approximately 84 living species worldwide; 22 are found in North America, with an additional four species in Mexican waters.
These fishes, the most primitive living vertebrates, are elongate and resemble eels. Some species reach a length of 3' (91 cm). Members of this superclass are easily recognized by their round, suctorial, jawless mouths. Hagfishes and lampreys do not have bone; the skeleton is formed of cartilage. Both groups lack scales and paired fins. The primitive gill openings are in the form of paired modified gill slits or pores.
Hagfishes are found only in marine environments. They are scavengers and often attack dying fishes caught in commercial nets.
Lampreys occur in both freshwater and marine habitats, but spawn only in fresh water. Adults may be parasitic; all larvae are filter feeders.
Agnathans first appeared during the Ordovician period, about 450 million years ago. Fossil agnathans differed from present forms in having the body covered with bony plates.
Class Myxini
Order Myxiniformes
This class contains the order Myxiniformes, the hagfishes. Myxiniformes, which is composed of a single family, is the only living order within this class. The most primitive of all living fishes, hagfishes are the only vertebrates whose body fluids are isotonic, the same density as sea water. Because they have few hard parts, their presence in the fossil record is poor; the oldest confirmed fossil records are from the Pennsylvanian period, about 300 million years ago.
6 genera and 43 species worldwide; 2 genera and 4 species in North America, plus 2 species confined to Mexican waters. Hagfishes occur in relatively deep offshore waters; all are completely marine. These primitive fishes have eel-like bodies and round, suctorial, jawless mouths. There are usually six to eight barbels around the mouth. The broad-based, triangular teeth are composed of a horny material, with one row on the tongue and one row on the roof of the mouth. These fishes have a single nostril near the tip of the snout (lampreys also have a nostril on the top of the head, but it is located between the eyes). The eyes are rudimentary, without a lens or iris, and usually not visible; in some genera a well-defined retina lies beneath the skin. As in lampreys, paired fins and scales are absent. The slightly rounded tail is composed of a skin fold. A conspicuous row of numerous mucous pores runs along the lower side of the body. All hagfishes are scavengers and feed primarily on dead or dying fish, which they locate by their sense of smell; they then rasp through the side of the prey and eat the flesh. They lay large elongate eggs, each enclosed in a horny shell. Unlike lampreys, hagfishes do not go through a larval stage. These fishes produce great quantities of slime, and are often known as slime eels.
Class Cephalaspidomorphi
Order Petromyzontiformes
Petromyzontiformes 35 This class contains the order Petromyzontiformes, the lampreys, plus three extinct orders. Petromyzontiformes is composed of a single family. These fishes are among the most primitive living vertebrates, with fossils dating to the Silurian period, 440 million years ago; lampreys first appeared during the Devonian period, about 410 million years ago.
6 genera and 41 species worldwide; 3 genera and 18 species in North America, plus 2 species confined to Mexican waters. Lampreys occur in freshwater and marine habitats (32 species are almost exclusively freshwater), but spawn only in fresh water and die after spawning. These primitive fishes have eel-like bodies; the round, suctorial, jawless mouth is used as a suction cup to attach to prey. In adults, the mouth has varying numbers of horny teeth. Lampreys have a single nostril between the eyes (hagfishes also have a nostril on the top of the head, but it is located farther forward near the tip of the snout). There are seven pairs of gill pouches, each with a pore-like external opening. As in hagfishes, paired fins and scales are absent. The larvae are blind and lack teeth, but have a filter-feeding screen in the mouth. As the larvae mature, they undergo a dramatic metamorphosis during which they lose the filter-feeding apparatus; the mouth becomes round, and the fins grow larger. Adults of some species are parasitic. Lampreys have up to 168 pairs of chromosomes, the highest number known for any vertebrate species.
This class, which belongs to the superclass Gnathostomata, contains two subclasses: Holocephali and Elasmobranchii. Based on the current scheme of classification, there are about 846 species in this class worldwide; 122 species occur in North American inshore waters to depths of 656' (200 m), and additional species are found in Mexican waters. A number of other species are confined to deeper waters offshore.
These fishes have cartilaginous skeletons, well-developed jaws, and paired fins supported by pectoral and pelvic girdles. Each pelvic fin on the male has a clasper, which facilitates internal fertilization. The teeth are actually modified scales; the pulp cavity of each tooth-like scale is surrounded by dentine that is covered by enamel.
There are three groups of fishes in this class: chimaerids (also known as ratfishes), sharks, and batoids (which includes sawfishes, skates, and rays). There are two simple ways to distinguish sharks from batoids: The gill slits of sharks are at least partly lateral and can be viewed from the side, while the gill slits of batoids are entirely ventral; also, the pectoral fins of sharks are not attached to the gill slits, while the pectoral fins of batoids are fused to the side of the head and usually form some kind of disk-shaped body. Chimaerids are the only cartilaginous fishes that have a single gill slit on each side.
These cartilaginous fishes, unlike most bony fishes, lack a swim bladder and must move constantly or they will sink to the bottom. They have a short intestine; the surface area is increased by internal spirals or folds for the absorption of digested food.
Subclass Holocephali
Order Chimaeriformes
The subclass Holocephali is composed of a single order, the Chimaeriformes, which contains three families worldwide; two families occur in North America. All species are marine, with most occurring in deep water to depths of nearly 7,750' (2,362 m). Only one of the 31 living species in the subclass Holocephali is found in inshore coastal waters to depths of 656' (200 m). These fishes (called chimaerids, ratfishes, or holocephalans) share many of the characteristics of sharks and rays, including a cartilaginous skeleton, urea in the blood and tissues, and a ventral mouth. They are unique among cartilaginous fishes in having the upper jaw fused with the cranium, a single gill slit on each side, the first dorsal fin with an erectile spine, and smooth unscaled skin; another distinguishing characteristic is the club-shaped clasper organ on the head of the male.
Subclass Elasmobranchii
This subclass includes the sharks and the batoids, or in other words, all living chondrichthyans except the members of the subclass Holocephali. According to the most recent classification scheme, the subclass contains 12 orders, with at least 46 families worldwide. Of these, 11 orders and 34 families occur in North American coastal waters to depths of 656' (200 m); a number of other species range farther offshore in deeper waters. The elasmobranchs share important characteristics with the holocephalans, including a cartilaginous skeleton, urea in the blood and tissues, and a ventral mouth. They differ in having five to seven separate gill slits on each side, placoid scales, and the upper jaw not fused with the cranium; in addition, males do not have clasper organs on the head. Nearly all elasmobranchs are marine, although about 28 species live occasionally or permanently in fresh water. These fishes are found in a wide range of depths, from shallow waters to depths of 18,000' (5,486 m) or more.
Order Hexanchiformes
This order is composed of two families, the Chlamydoselachidae and the Hexanchidae, both found in North America. The Chlamydoselachidae consists of a single wide-ranging species, Frill Shark (Chlamydoselachus anguineus), which in North America is known only from the eastern Pacific; it is unique among living sharks in having six wrinkled ("frilled") gill covers, together with an unusually slender elongate body and a snake-like head and mouth. The eyes lack nictitating membranes. Members of this order have a spiracle and six to seven pairs of gill slits. No spines are associated Cow Sharks 43 with the single dorsal fin, which is located posteriorly. These sharks have anal fins.
Order Squaliformes
This order formerly included all sharks except those in the orders Hexanchiformes and Heterodontiformes. As now constituted, it contains eight families, five of which are found in North American inshore waters. In addition, there are five species in Mexican waters, and a number of species in deeper offshore waters. These sharks have two dorsal fins, with or without spines, and the anal fin is absent. They have a spiracle and five pairs of gill slits. The eyes lack nictitating membranes. Many squaliform sharks are small and occur in deep water; some are bioluminescent. A few are common inshore species, particularly certain members of the genus Squalus in the family Squalidae.
This order consists of a single family: 1 genus with 12 species worldwide; 2 species in North America (1 Atlantic, 1 Pacific). This group was previously included in the order Squaliformes. Found in temperate and tropical waters, these bottom-dwelling sharks superficially resemble skates and rays, with whom they share a disk-like body; they differ in having the large pectoral fins separated from the head by a deep groove or notch. There are five gill slits on each side, hidden in the groove and not usually visible from above. Angel sharks have large spiracles, almost terminal mouths, and barbels. The two dorsal fins are located near the caudal fin and a row of tubercles down the center of the back. These fishes lack an anal fin.
This order consists of a single family: 1 genus with 8 species worldwide; 1 species in North America, plus 1 species confined to Mexican waters. These bottom-dwelling sharks occur in tropical and subtropical waters of the Pacific and Indian Oceans. They have deep, laterally compressed bodies, and are unusual in having a combination of low crushing teeth in the back of the jaws, two dorsal fins (each with a stout spine in front), and an anal fin. Bullhead sharks have a spiracle and five pairs of gill slits. The eyes lack nictitating membranes.
Order Orectolobiformes
Previously included in the order Squaliformes, this group consists of seven families, two of which occur in North America. These sharks have an anal fin and two spineless dorsal fins. The mouth is very short, confined to the area well in front of the eyes. Specialized nostrils have prominent grooves accompanied by barbels in most species. Members of this order have a spiracle, varying in size from from small to large, usually below each eye. Most species have five small gill slits, with the fifth slit on each side often overlapping the fourth behind the insertion of the pectoral fin.
3 genera and 3 species worldwide; 1 species in North America. Nurse sharks have a small spiracle below each eye. The short nostrils have short to moderately long barbels, without lobes or grooves around the outer edges. This family was formerly included in the carpet shark family (Orectolobidae).
1 species worldwide. These enormous filter-feeding sharks are usually seen on the surface far offshore. They have a spiracle behind each eye and five pairs of gill slits. The checkered color pattern, humpback, and large lunate tail distinguish whale sharks from all other sharks.
Order Lamniformes
This group of sharks, previously included in the order Squaliformes, contains seven families; six families occur in North America. The goblin shark family (Mitsukurinidae), which consists of one bizarre, deep-water species, was only recently recorded off California. The megamouth shark family (Megachasmidae), first formally described in 1983, has also been discovered off the coast of California. Members of this order have an anal fin and two spineless dorsal fins. There are five gill slits on each side; the last two are sometimes located above the pectoral fin. These fishes usually have a small spiracle behind each eye. The mouth extends well behind the eyes, which lack nictitating membranes.
2 genera and 4 species worldwide; 2 genera and 3 species in North America (2 Atlantic, 1 Pacific). These sharks have five pairs of gill slits of medium length. The two dorsal fins are of about equal size, and the caudal fin is only slightly elevated. These characteristics, together with the long tricuspid teeth, distinguish sand tigers from all other sharks.
1 genus with 3 species worldwide; 2 species in North America, plus 1 species confined to Mexican waters. These distinctive sharks have an extremely long caudal fin. The large first dorsal fin is located at about mid-body; the second dorsal fin is much smaller. Thresher sharks have five gill slits on each side; the third to fifth slits are over the pectoral fin insertion.
1 species worldwide. These sharks are found in temperate waters throughout the world. Their general body shape is nearly identical to that of the mackerel sharks (family Lamnidae), with a distinct keel on the caudal peduncle and caudal lobes of almost Mackerel Sharks 53 equal size. Basking sharks, in contrast to mackerel sharks, are plankton feeders, and in association with this have a cavernous mouth with vestigial teeth that are greatly reduced in size; long, horny, deciduous gill rakers, for straining prey from the water; and five very long gill slits that nearly meet under the throat. Another difference between the families is that adult basking sharks may develop notably elongate snouts.
3 genera and 5 species; all found in North America. These sharks have torpedo-shaped bodies and large teeth that are used to capture prey such as fishes, squids, and marine mammals. There are five long gill slits on each side, with the fifth located in front of the pectoral fin insertion. Some species have spiracles. Similar to basking sharks (family Cetorhinidae), mackerel sharks have a distinct keel on the caudal peduncle and caudal fin lobes of almost equal size.
Order Carcharhiniformes
Previously included in the order Squaliformes, this 56 Carcharhiniformes group is composed of eight families, five of which occur in North American inshore waters. Other species may occur offshore in waters deeper than 656' (200 m). These sharks have two dorsal fins, without spines at the bases, and an anal fin. There are five gill slits on each side; the last one to three are located over the pectoral fin. Gill rakers are absent, and spiracles may be present. The eyes have nictitating folds or membranes.
15 genera and at least 96 species worldwide; 6 genera and at least 5 species in North America. These fishes are found most abundantly in the western Pacific; five of the North American members of this family occur in inshore waters, and at least five other species occur in deeper offshore waters. Small and bottom-dwelling, cat sharks are among the most spectacularly marked sharks, with blotches, spotting, and vermiculations on their bodies. The fifth gill slit is located over the pectoral fin insertion. In most species the dorsal fins are far back on the body. The upper lobe of the caudal fin is longer than the lower.
9 genera and 41 species worldwide; 3 genera and 8 species in North America, plus 1 species confined to Mexican waters. Relatively small, bottom-dwelling sharks of coastal waters, hound sharks are also known as smoothhounds. The jaws have moderately long labial furrows, and the anterior nasal flaps are usually not slender or barbel-like. Spiracles are present. All species are viviparous. Members of this family resemble the requiem sharks (family Carcharhinidae), and were previously included in that family. They are smaller than requiem sharks and have more numerous smaller, compact, crushing teeth; these differences, however, are by no means absolute.
12 genera and about 50 species worldwide; 5 genera and 20 species in North America, plus 2 genera and 4 species confined to Mexican waters. Until recently, the North American hound sharks (family Triakidae) and hammerhead sharks (family Sphyrnidae) were included in this group, the largest family of sharks. Although most species are pelagic, the majority of these do not regularly range beyond the limits of the continental shelf. The larger species are dangerous, but the majority are too small to be considered serious threats to people. Because they resemble one another so closely, many requiem sharks are difficult to identify, especially those in the largest genus, Carcharhinus. All family members have two spineless dorsal fins, with the first fin usually larger than the second; some Carcharhinus species have a low dermal ridge between the dorsal fins. The upper caudal fin lobe is elongate and pointed upward. There are five pairs of gill slits. The teeth are blade-like cusps, with smooth or serrate edges; it is unusual for more than one row of teeth to be functional at a time. Morphology of the teeth is important in identification, as are such characteristics as snout length and the size and position of the fins.
1 genus with 8 species worldwide; 4 species in North America, plus 2 species confined to Mexican Pacific waters. These unusual fishes have greatly depressed and laterally expanded heads. The position of the eyes, on the lateral expansion, gives hammerhead sharks vision in all directions and better depth perception. The patterns of the head pores (the ampullae of Lorenzini, which are involved in the detection of electrical impulses) are taxonomically diagnostic, a characteristic unique among sharks. The teeth are usually moderately slanted, sometimes serrate. The two dorsal fins are spineless, with the first fin usually larger than the second. The upper caudal fin lobe is long and pointed upward. Young inhabit coastal waters, and adults of larger species are primarily oceanic. These sharks are voracious predators, and the biggest species are dangerous to people.
Order Torpediniformes
This order contains two families, both of which are found in North America. These fishes have soft loose skin. A powerful electric organ, derived from branchial muscles, is located on or near the head. The eyes are small or occasionally absent or vestigial. Members of this order have well-developed caudal fins and, when present, one or two dorsal fins.
9 genera and about 24 species world- wide; 1 species in North America, plus 1 genus with 3 species confined to Mexican Pacific waters. These rays are often placed in the closely related torpedo electric ray family (Torpedinidae). They have disk-shaped bodies that are anteriorly rounded. The stout jaws have strong labial cartilages.
2 genera and 14 species worldwide; 1 genus with 2 species in North America (1 Atlantic, 1 Pacific). Members of this family have rounded bodies that are more or less straight across the anterior edge. The extremely slender jaws lack labial cartilages. Dorsal and caudal fins are usually present and well developed. These rays stun their prey and protect themselves with specialized muscles, located near the head, that produce a powerful electric charge, delivering more than 200 volts. Electric rays are found in all oceans, from shallow bays to great depths.
This order consists of a single family: 2 genera and 6 species worldwide; 1 genus with 2 species in North America. Sawfishes are shark-like fishes that have two well-developed dorsal fins and a prominent caudal fin. The most conspicuous feature is the saw, an extremely elongate, blade-like snout armed on both sides with large teeth of equal size and embedded in deep sockets. All species lack barbels. Sawfishes live close to shore, chiefly over sand or mud and seldom in water deeper than 30' (9 m). Certain species are known to ascend rivers. Due partly to the marketing of the saws as curios, sawfishes are often killed indiscriminately; their numbers have declined dramatically in parts of the world. In addition, they are considered destructive nuisances by commercial anglers because they easily become entangled in fishing nets. Sawfishes are now protected in some areas, including North America.
Order Rajiformes
Recent reclassifications have reduced this order to three families, thornbacks (Platyrhynidae), guitarfishes (Rhinobatidae), and skates (Rajidae), all of which occur in inshore and deeper North American waters and adjacent Mexican Atlantic and Pacific waters. All of these fishes have easily recognizable shapes. In skates the body is greatly depressed, with the pectoral fins expanded to form a disk. Although similar to skates, thornbacks and guitarfishes have a more robust, shark-like body posterior to the pectoral fins. The tail is usually distinct from the body. All species have a pair of spiracles and five pairs of gill slits. Members of this order usually have two dorsal fins without spines.
1 genus with 5 species worldwide; 1 species in North America. These fishes are found in warm-temperate and continental shelf waters in the Pacific from California to Japan, China, and India, and are also known off western Africa. The skate-like body of thornbacks retains some of the characteristics of sharks. The portion of the body behind the pectoral fins is robust, not depressed as in skates and rays. There are five pairs of gill slits on the underside of the body. These fishes have two dorsal fins and a large caudal fin. The body shape, tail, and habits of this family are very similar to those of the related guitarfishes (family Rhinobatidae, which includes six genera and about 40 species, with two genera, Rhinobatos and Zapteryx, and three species in North America). Thornbacks, however, have a more rounded snout and one to three large hooked spines on the back and the tail. Most species are ovoviviparous.
18 genera and more than 200 species worldwide; 6 genera and 24 species in North America (14 Atlantic, 10 Pacific), plus 5 species confined to Mexican waters. Four of the North American species found in the Pacific are restricted to Alaskan waters. These fishes have flat, disk-like bodies formed by large "wings” that are shaped by the pectoral fins and attached to the head and body; these wings are used for propulsion. There are usually two small spineless dorsal fins. When present, the caudal fin is rudimentary. These fishes have large thorns on the midline of the back, and males have long prominent claspers used in mating. Skates spend their time on the bottom, partially buried in the mud or sand, usually in inshore waters.
Order Myliobatiformes
This order includes six families, all of which are found in North America. Members of the order inhabit shallow or mid-depth waters and are mainly tropical, with relatively few species found in temperate seas. Although most are bottom dwellers, a number are pelagic. Some species enter or are confined to fresh water. Almost all species have at least one long barb on the tail, which may be accompanied by poison sacs at the base. The tail is long and whip-like, usually without a caudal fin, except in the round stingrays (family Urolophidae), which have a short stout tail and a small caudal fin. A dorsal fin is sometimes present. The body is smooth or covered with denticles and large spines. These fishes do not have electric organs. They are ovoviviparous and give birth to living young.
9 genera and about 70 species world- wide; 2 genera and 6 species in North America (4 Atlantic, 1 Pacific, 1 shared), plus 1 genus and 4 species confined to Mexican waters. This family previously included the round stingrays and butterfly rays, which are now placed in their own families (Urolophidae and Gymnuridae, respectively). Whiptail stingrays have greatly depressed disks. Tubercles or prickles are present in some species, especially on the dorsal midline of the disk. The pectoral fins extend forward beyond the mouth, and the dorsal fin is absent. The long, whip-like tail is distinct from the body; it lacks an obvious caudal fin and has a poisonous spine. These stingrays can inflict wounds characterized by intense pain and slow recovery, and are therefore potentially dangerous to swimmers and waders. (To prevent an encounter, shuffle your feet as you walk through the water so you nudge the ray on the side or from underneath; it is likely to swim away.) They stir the bottom with their pectoral fins in order to dislodge worms, mussels, small crustaceans, and other prey.
2 genera and about 35 species world- wide; 1 genus with 2 species in North America (1 Atlantic, 1 Pacific), plus 7 species confined to Mexican waters. These fishes are found in warm-temperate regions of the Atlantic, Pacific, and Indian Oceans. They resemble whiptail stingrays (family Dasyatidae), the most evident differences being that round stingrays have a slightly shorter tail with an obvious caudal fin; in addition, unlike the whiptail stingrays, some species have a dorsal fin.
2 genera and about 12 species world- wide; 1 genus with 3 species in North America (2 Atlantic, 1 Pacific), plus 1 species confined to Mexican waters. Butterfly rays have an extremely flat disk, shaped like a broad rounded diamond, twice as wide as it is long; the disk is about one and one-half times wider than the length of the body from the tip of the snout to the tip of the tail. The tail is slender, whip-like, and very short (much shorter than the disk), without a caudal fin; a small spine is usually present on the tail. All species lack a dorsal fin. The mouth is small, with numerous tiny pointed teeth. The two largest species are known to have disks to 7' (2.1 m) wide, and there have been unconfirmed reports of individuals with disks as wide as 13' (4 m).
4 genera and about 24 species world- wide; 2 genera and 4 species in North America (2 Atlantic, 1 Pacific, 1 shared), plus 2 species confined to Mexican Pacific waters. These rays, found in tropical and temperate seas, have robust bodies with roughly falcate pectoral fins; the entire disk is wider than it is long. The anterior parts of the pectoral fins form one or two subrostral lobes under the snout; the pectoral fins themselves are narrow and pointed near the tips. The eyes and spiracles are located on the sides of the head, which is separate from the rest of the disk. Eagle rays have long tails, distinct from their bodies; there is a small fleshy dorsal fin on the tail base, behind which is a venomous spine. The pectoral fins function in a flapping motion, which serves to propel the fish through the water; this motion is different from the undulating movement of skates (family Rajidae), whiptail and round stingrays (Dasyatidae and Urolophidae), and butterfly rays (Gymnuridae).
1 genus with about 5 species worldwide; 1 species in North America, plus 1 species confined to Mexican Pacific waters. Members of this family, found in tropical to warm-temperate seas, resemble the closely related eagle rays (family Myliobatidae) and mantas (Mobulidae); similar to the mantas, the pectoral fins of these rays are deeply divided into subrostral lobes. All species have a small dorsal fin. Cownose rays are unique among myliobatiform fishes in having heads with a concave anterior depression.
2 genera and 13 species worldwide; 2 genera and 3 species in North America (1 Atlantic, 1 Pacific, 1 shared), plus 3 species confined to Mexican Pacific waters. In contrast to cownose rays (family Rhinopteridae) and eagle rays (Myliobatidae), mantas lack large tooth plates. The pectoral fins are subdivided anteriorly and modified into two separate cephalic fins (on the head). The posterior edges of the pectoral fins are falcate. The small dorsal fin is located on the tail; all North American mantas have spineless tails. These fishes occur worldwide in tropical and warm to temperate seas, and feed on large planktonic crustaceans or schools of small fishes that they strain with the branchial sieve.
Living bony fishes are separated into two classes, Sarcopterygii and Actinopterygii, but only the latter, the ray-finned fishes, occurs in North America. Actinopterygii contains most of the known marine and freshwater fishes. This class is the most valuable to people because of the large number of species that support commercial and sport fisheries. Worldwide, there are 45 orders with nearly 24,000 species in the class (about 40 percent in fresh water); 38 orders with roughly 2,500 species occur in North America (about 800 species native to fresh water) north of Mexico.
Ray-finned fishes are characterized by the presence, in most species, of fins with soft rays or spines, one of several types of scales, a single pair of gill openings, branchiostegal rays, a swim bladder or functional lung, and a skeleton that is at least partially composed of bone.
The eggs and embryos are never enclosed in cases, and fertilization is usually external. Some members of this class live for less than a year, whereas others live for more than 100 years.
Usually considered to be the most recent in evolutionary terms, this class first appeared in the Silurian period, about 440 million years ago. Many species have Paddlefishes 85 become so specialized that they face extinction when some aspect of their habitat is threatened.
Order Acipenseriformes
This order, confined to the Northern Hemisphere, contains two families, the sturgeons (Acipenseridae) and the paddlefishes (Polyodontidae), both of which occur in North America. These fishes are found in fresh water; however, some are anadromous. They are among the largest freshwater fishes, and are the remnants of an ancient and primitive group. Members of this order have largely cartilaginous skeletons, upper jaws that are not united with the skull, and heterocercal caudal fins.
4 genera and 24 species worldwide; 2 genera and 8 species in North America. This family includes anadromous and freshwater fishes. Sturgeons are large fishes with comparatively elongate snouts. They have a total of five rows of bony plates on the body (one dorsal row, two mid-lateral rows, and two ventrolateral rows), scale-like plates on the skin between the bony plates, and bony plates covering the head. There are four barbels anterior to the ventral mouth, which lacks teeth. Species in the genus Acipenser have two smooth lobes on the lower lip, whereas species in Scaphirhynchus have four papillose lobes. The dorsal and anal fins are located on the rear one-third of the body. Females are usually larger and mature later than males.
2 genera and 2 species worldwide; 1 species in North America. This freshwater family is represented by one species in the Mississippi River system and one species in the Yangtze River of China. Paddlefish (Polyodon spathula) is probably the most distinctive of all North American fishes, due to its elongate snout that expands into a thin flat paddle; its body is covered with smooth skin similar in appearance to that of the freshwater catfishes (family Ictaluridae).
This order consists of a single family: 2 genera and 7 species worldwide; 2 genera and 5 species in North America, plus 1 species confined to Mexico. These fishes are found in eastern North America and Central America south to Costa Rica and Cuba. Gars are predominantly freshwater (some species enter brackish and marine waters). They are long, slender, predatory fishes covered with interlocking ganoid scales that protect them from most predators. Extremely hardy, gars typically inhabit quiet, weedy, often stagnant backwater areas. They have elongate jaws with needle-like teeth, and are equipped with a vascularized swim bladder to permit aerial respiration. The single dorsal fin is located posteriorly on the body above the anal fin; the abbreviated heterocercal caudal fin is rounded.
This order of ancient and highly predatory fishes consists of a single family: 1 species native to fresh waters of eastern North America. Fossil records are known from freshwater and marine deposits dating from the Jurassic period, 213 million years ago. Bowfins are a transitional group, related to the gars (family Lepisosteidae), but possessing some characteristics of bony fishes. For example, the primitive skeleton consists of bone and cartilage, but its vertebrae are concave at each end, a characteristic of bony fishes. These fishes have bony plates covering the head and a bony gular plate. There is a single dorsal fin, and the abbreviated heterocercal caudal fin is rounded.
This order consists of a single family: 1 genus with 2 species confined to fresh waters of North America. Mooneye fossils are known from the Cretaceous period, approximately 145 million years ago, in China. Representatives of this group probably entered North America from China via rivers and streams that traversed the Bering land bridge. Mooneyes may be confused with the herrings (family Clupeidae), but can be distinguished by the presence of teeth on the tongue and jaws, the absence of scutes on the belly, and the position of the dorsal fin, which is over the anal fin. All family members have a lateral line. This group was formerly included in the order Osteoglossiformes.
Order Elopiformes
This order consists of two families, both of which occur in North America. Members of this order are silvery elongate fishes with spineless fins. The pelvic fins are abdominal, and the pectoral fins are inserted below the mid-side of the body. The single dorsal fin is located at mid-body, and the caudal fin is forked. These fishes lack adipose fins. Scales are cycloid; each pectoral and pelvic fin has a large axillary scale. An adipose eyelid is present. The gular plate is well developed on the underside of the head. Members of this order share a ribbon- like leptocephalus larval stage with the closely related orders Albuliformes and Anguilliformes, a characteristic that is presumed to be indicative of a natural phylogenetic relationship among these groups.
1 genus with at least 6 species worldwide; 3 species in North America (2 Atlantic, 1 Pacific), including a presumably unnamed Caribbean species that ranges north into the Gulf of Mexico and along the southern U.S. Atlantic coast. Found throughout the world in tropical to warm-temperate seas, tenpounders (also known as ladyfishes) are silvery, herring-like fishes with elongate streamlined bodies. The Elopidae at one time also included the tarpons (now in the family Megalopidae); tenpounders differ from tarpons in having a more slender body, much finer (thus more numerous) scales, more branchiostegal rays, more pelvic and dorsal fin rays, no posterior extension to the dorsal fin, fewer anal fin rays, unbranched tubes in the lateral line, and the swim bladder not lying against the skull. The taxonomy of the genus Elops is poorly understood; the different species closely resemble one another and differ primarily in the number of myomere segments in the larvae, and in the numbers of vertebrae, gill rakers, and lateral line scales in adults.
1 genus with 2 species worldwide; 1 species in North America. Tarpons, found in tropical seas worldwide, differ from the closely related tenpounders, also known as ladyfishes (family Elopidae, in which they were formerly included), in having a deeper and more robust body, much coarser (thus fewer) scales, fewer branchiostegal rays, fewer pelvic and dorsal fin rays, a posterior extension to the dorsal fin, more anal fin rays, branched tubes in the lateral line, and the swim bladder lying against the skull.
Order Albuliformes
This order contains three families, all of which are found in North America; the family Albulidae (boneMorays fishes) occurs in shallow inshore waters, and the Halosauridae (halosaurs) and Notacanthidae (spiny eels) in deep offshore waters. Members of this order share a leptocephalus larval stage, absence of an adipose fin, and other basic characteristics with the closely related orders Elopiformes (in which they were once placed) and Anguilliformes. They differ from elopiform fishes in having a weakly developed gular plate, the insertion of the pectoral fins sometimes high on the body (family Halosauridae), fin spines sometimes present (family Notacanthidae), and the caudal fin not always forked (the caudal skeleton is greatly reduced in both Halosauridae and Notacanthidae). Adults of the family Albulidae are conventionally shaped fishes, whereas adult halosaurs and notacanthids are elongate fishes whose body shapes partially reflect their close relationship to anguilliform fishes.
1 genus with probably 7-8 species worldwide; 2 species (1 unnamed) in North America. One-third of all North American bonefishes are found in tropical waters of the western Atlantic and eastern Pacific. These fishes have an elongate fusiform body with an undivided dorsal fin and a large caudal fin. Their eggs hatch into leptocephalus larvae, which move offshore to the open ocean where they spend their early lives before returning inshore as juveniles.
Order Anguilliformes
This order includes three suborders and 15 families worldwide. Within the three suborders and nine families found in North America, virtually all species occur in inshore marine waters; one species occurs in fresh water. Many species are found in deeper waters offshore and are rarely seen. These long, snake-like fishes lack pelvic fins or girdles, premaxillary bones, and spines in the fins. Most eels are unscaled; freshwater eels (family Anguillidae) have very small, deeply embedded cycloid scales. The pectoral fins are often rudimentary or absent. The caudal fin is sometimes absent; when present, it is continuous with the dorsal and anal fins. Gill rakers are absent, and the gill openings are usually very small. Many of the bones usually found in the heads of fishes are absent or fused. Members of this order share a ribbon-like leptocephalus larval stage with the closely related orders Elopiformes and Albuliformes, although in some families the leptocephalus stage is of relatively short duration. The leptocephalus stage is highly pelagic; this mobility is probably a major factor in the unusually wide distributions of certain eel species.
1 genus with 15 species worldwide; 1 species in North America. Unlike other eels, members of this family have small scales embedded in the skin. In addition, they have pectoral fins, and the dorsal and anal fins are continuous with the caudal fin. After reaching sexual maturity, the two Atlantic freshwater eel species migrate to the Sargasso Sea to spawn. The eggs hatch into leptocephalus larvae that pass through several stages as they transform into adults. Apparently only the females ascend rivers, where they remain for a number of years.
15 genera and roughly 200 species worldwide; 6 genera and 19 species in North America (5 Atlantic, 1 Pacific), plus 4 genera and 21 species confined to Mexican Atlantic and Pacific waters. These fishes are found throughout the world, mostly in reefs and rocky areas of inshore tropical oceans. The body is heavy and compressed in some species, more so than in most other eels; in such heavy- bodied species, the forehead is elevated in adults. Most have long, fang-like teeth in the jaws and on the roof of the mouth; adults of some species have low, molar-like teeth. Morays are also distinguished by having an unscaled body; a small round gill opening on each side of the head; lateral line pores on the head but not the body; a posterior nostril high on the head, usually above the front portion of the eye; and reduced gill arches. They lack pectoral fins, and the reduced tail is continuous around the tip of the body. The leptocephalus larval stage is relatively short-lived, and very small transformed morays are encountered more frequently than in other eels. Morays are most readily confused with those species of the family Chlopsidae, appropriately called false morays, which lack pectoral fins. Many chlopsids have pectoral fins, but for those that do not, the only obvious external difference between the two families is the position of the posterior nostril, which is ventrally placed in the chlopsids (dorsally situated in the morays).
52 genera and about 250 species worldwide; 17 genera and 36 species in North America (32 Atlantic, 4 Pacific), plus 10 genera and 37 species confined to Mexican waters. Found in tropical to warm-temperate inshore waters, these fishes comprise a morphologically diverse family of unscaled eels, some of which have reduced or absent fins and resemble snakes. Some are very colorful, and a number of species are active in the daytime. Within the restricted framework of eel morphology, there are broad differences among species. The snout varies from rounded to pointed, although the latter condition is probably more prevalent. Pectoral, dorsal, and anal fins are usually present, but some species may lack one or more of these fins; in extreme cases, some lack fins altogether. The position of the gill openings may vary from the underside to the side of the body or some position in between. The posterior nostril is located on or near the upper lip and, like the anterior nostril, may be either a simple opening or situated at the end of a tube. The teeth are fang-like in some species and blunt in others. The family is divided into two subfamilies: the Ophichthinae (snake eels), which have hard-tipped tails usually without visible caudal fin rays; and the Myrophinae (worm eels), which have tails with flexible tips and short but visible caudal fin rays. Those species that burrow into hard bottoms in relatively deep water are usually difficult to collect and may be known from very few specimens. For similar reasons, new species continue to be discovered, probably more so than for any other family of eels.
Order Clupeiformes
This order consists of five families: the herrings and the anchovies, both of which are found in North American waters, and three smaller families. The majority of these usually small, delicate, silvery fishes are marine. Anchovies and herrings usually have laterally compressed bodies (a few herring species have rounded bodies), normally without dark pigment. Members of this order are rather primitive, with such features as abdominal pelvic fins, pectoral fins low on the sides of the body, no adipose fin, fins lacking spiny rays, and cycloid scales that in many species are highly deciduous. They are unique in having a peculiar connection between the swim bladder and the inner ear, together with special characteristics of the portion of the skeleton that supports the caudal fin. The pectoral and pelvic fins may each have a large axillary scale in the posterior angle between the fin and the body. The dorsal fin is never divided into segments, but in some cases the last ray may have a long extension. A lateral line is absent, but in some species sensory canals on the head extend onto the shoulder region. All have a single trils. Most species have numerous long, fine, closely set gill rakers attached to the inner sides of the gill arches; these are used to strain small planktonic organisms from the water. In some species the number of gill rakers increases with size and age; in other species the number remains stable throughout adult life. The number of gill rakers, as well as the number of branchiostegal rays, are often of considerable taxonomic importance. Many species swim in large compact schools, usually numbering in the thousands. Many anchovies and herrings are important as forage for larger carnivorous fishes, and some species are of commercial importance.
16 genera and 139 species worldwide; 4 genera and 13 species in North America (9 Atlantic, 4 Pacific), plus 1 genus and 17 species confined to Mexican waters. There is an unusually high percentage of species concentrated in the tropical eastern Pacific region. Some occur in fresh water, although rarely in North America. Anchovies are small, usually not exceeding 4” (10 cm) in length, delicate, and moderately laterally compressed. These fishes are unmistakable, due to the combination of a silvery translucent body, often with a bright silvery stripe along the side, large eyes, and a very large inferior mouth coupled with an overhanging conical snout. The gill arches extend well forward on the floor of the mouth, nearly to the tip of the lower jaw, and contain numerous closely spaced gill rakers. The pelvic fins are abdominal, and the pectoral fins are low on the body. The caudal fin is deeply forked. The large cycloid scales are deciduous; unlike in herrings, the scales do not form a keel on the midline of the belly. Many anchovies are similar in appearance but differ in the number of fin rays, position of the dorsal fin relative to the anal fin, shape and length of the maxilla, and number of gill rakers. They play an invaluable role in the food web, and are eaten extensively by predators such as mackerels and bluefishes. Widely used for bait and food, these fishes also are important commercially.
56 genera and about 180 species worldwide; 11 genera and 33 species in North America, plus 1 genus and 5 species confined to Mexican waters. Members of this large, primarily saltwater family have variable body shapes. The clupeid mouth is typically large and terminal, with the lower jaw projecting beyond the upper; however, the lower jaw is deep and the maxilla is broad posteriorly. The anal fin is larger than the dorsal fin, which is at about mid-body. There is no lateral line. Most herring species have scutes, modified cycloid scales with keel-like ridges, on the belly.
Order Cypriniformes
This is the second-largest order of fishes; there are five families worldwide, two of which occur in North America. This is usually the dominant group of freshwater fishes, very rarely entering brackish water, and adapted to the most extreme freshwater environments. Members of this order have a single rayed dorsal fin, and most species lack fin spines. The scales are cycloid. These fishes have a series of modified vertebrae connecting the swim bladder with the inner ear, which facilitates an acute sense of hearing.
210 genera and about 2,000 species worldwide; 45 genera and 254 species native to North America north of Mexico, plus 5 genera and 41 species confined to Mexico. The largest family of fishes in the world, Cyprinidae has the most extensive continuous distribution of any family of freshwater fishes; carps and minnows occur throughout North America, Europe, Asia, and Africa, but are absent from South America. The widespread distribution and abundance of these fishes make them very important in the ecology of freshwater ecosystems. They have jaws without teeth and cycloid scales, and lack an adipose fin. Some species are as small as 1/2" (12 mm) long, and some are as big as 9' (3 m). The largest North American species, Colorado Pikeminnow (Ptychocheilus lucius), reaches a length of 5’ (1.5 m).
14 genera and 73 species worldwide; 13 genera and 63 species in North America, plus 6 species in Mexico. Suckers are small to moderately large, bottom-dwelling freshwater fishes that inhabit rivers, creeks, and lakes. They usually have ventral mouths with thick lips and jaws without teeth. In most species the mouth can be extended ventrally during feeding. They lack adipose fins and barbels. There are at least 10 rays in the dorsal fin, and the short anal fin is placed well back on the body. Members of the genus Catostomus, which occur mainly in the western United States in somewhat restricted ranges, can be distinguished by a cylindrical body with a flat or rounded head and an inferior horizontal mouth with thick fleshy lips that are either plicate or have papillae. Catostomus suckers have fewer than 20 dorsal fin rays, and more than 55 scales in the lateral line.
Order Characiformes
This order contains 10 families, only one of which occurs in North America. These fishes are found from the southwestern United States south to South America and in Africa. Most are small and colorful, and many are utilized in the aquarium fish trade. Other species are important food fishes.
About 170 genera and 900 species worldwide; 1 species in North America north of Mexico. Members of this large family, one of the two families of freshwater fishes that occur in South America and Africa, are found from Texas and New Mexico south through Central and South America and in Africa. The family includes herbivorous fishes as well as the carnivorous piranhas (genus Serrasalmus). Most characins have jaws with teeth and adipose fin, and all lack barbells.
Order Siluriformes
This large order contains 34 families. In North America there are two native families, plus one in Mexico; there are three introduced families of freshwater catfishes in the United States. These marine and freshwater catfishes are distributed in temperate and tropical waters worldwide. They are closely related to the Cypriniformes; members of both groups have an apparatus that connects the swim bladder with the inner ear, providing an acute sense of hearing. Many species are commercially important as food, sport, and aquarium fishes.
6 genera and 39 species confined to fresh waters of North America, plus 1 genus with 7 species in Mexico. These catfishes are found east of the Rocky Mountains, from southern Canada south to Guatemala. They range in length from 2” (5 cm) to more than 5’ (1.5 m). They have four pairs of barbels, an adipose fin, and each dorsal and pectoral fin has a single spine. In some species the pectoral fin spines have serrations. The madtoms (genus Noturus) are equipped with a venom gland at the base of the pectoral fin spine, which is often grooved, enabling them to inflict a painful sting. Species in the genera Ameiurus, Ictalurus, and Pylodictus are important sport and food fishes.
13 genera and about 100 species worldwide; 1 species introduced in North America. These freshwater catfishes are native to Africa, Syria, India, and the area encompassed by Java, Borneo, and the Philippines. Many are important food fishes, some attaining lengths of 3' (1 m). Members of this family have a unique accessory respiratory organ, which rises from the gill arches, that enables them to breathe air by increasing the surface area for absorption of oxygen. This adaptation allows some species to leave the water and move about on land. The dorsal fin is long, with usually more than 30 rays, and lacks a spine at the anterior end. The adipose fin is often absent.
About 14 genera and about 120 species worldwide; 2 genera and 3 species in North America. The taxonomy of the sea catfishes, found in tropical to warm-temperate waters throughout the world, is not well-known. Ariidae is one of only two predominantly marine catfish families, although both families include species that either enter or live permanently in fresh water. They superficially resemble the completely freshwater North American bullhead catfishes (family Ictaluridae), with which they share unscaled skin, the presence of an adipose fin, three pairs of barbels on the chin and lower jaw in most genera (certain sea catfish genera, including Bagre, have two pairs), and a forked caudal fin (not present in all bullhead catfish genera); in addition, members of both families have the anteriormost pectoral and dorsal fin rays coalesced into a hard spine. The most obvious external differences between the two families is that the Ariidae lack nasal barbels (bullhead catfishes have one pair on the rim of the rear nostril) and the front and rear nostrils are set close together (widely separated in the Ictaluridae). Sea catfishes are oral incubators; some species carry the large, marble-size eggs for up to three months prior to hatching.
About 80 genera and almost 600 species worldwide; 2 genera and 4 species introduced in North America north of Mexico. This freshwater family is native to South America and ranges north in Central America to Costa Rica. It is a diverse group, found in a variety of habitats, ranging from lowland rivers to high-gradient mountain streams. Family members have a ventral mouth and bony plates covering the body; most have a flat ventral body surface. When present, the adipose fin is preceded by a spine. Some species are important in the aquarium trade.
Order Esociformes
There are two families in this small order, both of which occur in North America. These freshwater fishes, confined to the Northern Hemisphere, are characterized by elongate to relatively elongate bodies, with the dorsal and anal fins located far back on the body. They lack adipose fins, and breeding males do not have tubercles. Fossil species of this order date back to the Cretaceous period, 145 million years ago.
1 genus with 5 species worldwide; 4 species in North America. Pikes and pickerels are predatory freshwater fishes. They have elongate, moderately compressed bodies with small cycloid scales, large heads with elongate flat snouts, and jaws with large sharp teeth. The dorsal and anal fins are located opposite each other far back on the body, and the caudal fin is forked. Most of the species found in North America are popular sport fishes.
3 genera and 7 species worldwide; 3 genera and 4 species in North America. These freshwater fishes are small, reaching a maximum length of about 8” (20 cm). They are very hardy, capable of withstanding extreme cold, and are able to utilize atmospheric oxygen. Under adverse conditions they are reputed to become dormant in mud. Members of this family have short snouts, non-protractile jaws with small teeth, cycloid scales on the head and body, and faint or absent lateral lines. The pelvic fins are small, and the caudal fin is rounded. The North American mudminnows are found in western Alaska and Washington, in the Great Lakes, and on the Atlantic coastal plain.
Order Salmoniformes
This order contains two families, both of which are found in North America. They include freshwater, marine, anadromous, and deep-sea species. All have soft-rayed fins, adipose fins, and abdominal pelvic fins. Most of these fishes are commercially valuable.
7 genera and 13 species worldwide; 6 genera and 10 species in North America, including 1 species introduced from Asia. Smelts are found in marine and freshwater environments in cold-temperate to arctic waters throughout the Northern Hemisphere. They resemble the closely related trouts and salmons (family Salmonidae) in many ways, including having a streamlined body, pelvic fins midway on the underside of the abdomen, low pectoral fins, an adipose fin, firmly attached small scales covering the body, and an incomplete lateral line. Smelts lack the axillary scale above the pelvic fin that is characteristic of trouts and salmons. During spawning, these fishes exhibit sexual differences, such as breeding tubercles and a modified anal fin in the male. They are popular sport fishes and are captured in nets from the shore. Smelts are important commercially, used for both food and bait.
11 genera and about 66 species worldwide; 7 genera and 39 species in North America north of Mexico (38 native, 1 introduced), plus 1 species in Mexico. These fishes occur in temperate fresh and salt waters of the Northern Hemisphere and have been widely introduced throughout North America. All salmonids have an adipose fin and an axillary scale above each pelvic fin, and most species have well-developed teeth in both jaws. The gill membranes extend far forward and are free of the isthmus. The swim bladder is connected to the alimentary canal, allowing these fishes to change depth rapidly. Many species exhibit significant sexual differences in color and morphology during the spawning season. Many trouts and salmons are important sport fishes.
Order Aulopiformes
This order contains 13 families, seven of which are found in shallow to deep marine waters of North America. Only the lizardfish family (Synodontidae) contains species that predominantly occur in inshore waters. Members of this order are soft-rayed fishes with abdominal pelvic fins; some families have an adipose fin. The scales are cycloid; certain species have luminescent photophores on the body. These features are also characteristic of the order Myctophiformes, in which the aulopiform fishes were formerly included. The separation of the Aulopiformes from the Myctophiformes is based on several specializations of the gill arches that are unique among bony fishes.
5 genera and 55 species worldwide; 3 genera and 11 species in North America. Found in tropical to temperate waters, members of this group are oblong or elongate, almost round in cross section, and reach lengths of 6-18' (15-46 cm). The mouth is large, wide, and slightly oblique, with the upper jaw bordered entirely by the premaxilla and a rudimentary maxilla extending well behind the eyes. The jaws bear numerous cardiform teeth, and teeth are also present on the tongue and roof of the mouth. These teeth, to gether with a pointed scaly head, give these fishes a distinctive lizard-like appearance, hence the collective common name lizardfishes. The abdominal pelvic fins have the inner rays either distinctly longer than the outer, or vice versa (depending upon genus). The dorsal fin is short and undivided. An adipose fin is present, and the caudal fin is forked. Lizardfishes are typically seen resting motionless on sand or mud bottoms. Post-larvae are transparent and have a series of black spots in the body cavity lining, the number and distribution of which are of taxonomic importance.
Order Lampridiformes
This morphologically diverse order of pelagic fishes contains seven families, five of which are found in North America. Some species have a unique protractile upper jaw. All have fins without true spines, and the pelvic fins are sometimes absent. One group (composed of two families) has a deep body, a symmetrical caudal fin, and a well-developed skeleton; this group includes the large, widely distributed, and commercially important Opah (Lampris guttatus). The other group (composed of five families) are among the most morphologically bizarre of all fishes, with a laterally compressed, ribbon-like body, a sometimes asymmetrical caudal fin, and a weak skeleton.
2 genera and probably 2 species worldwide; 1 species in North America. Oarfishes have extremely elongate bodies and relatively blunt heads without extended snouts. The eyes are small, and teeth are absent. The pelvic fins are extremely slender and elongate, each with a single ray and a paddle-like membrane near the tip. The bright red dorsal fin is extremely long, extending the entire length of the fish from just behind the tip of the snout to the base of the tail; the first few rays are elongate, highly elevated as a flag-like crest on the head, and the remainder of the fin is extremely low in relation to the body. The anal fin is absent, and the caudal fin is tiny. These fishes are unscaled, but have tubercles on the skin. They lack a swim bladder. The number of gill rakers differs in the two species, suggesting different feeding habits.
Order Percopsiformes
This order contains two families, both of which are confined to the fresh waters of North America north of Mexico. These fishes are small and usually robust, with relatively large heads. The dorsal fin is preceded by up to four weak spines, and the anal fin by up to three weak spines. When present, the pelvic fins are situated behind the pectoral fins and are composed of eight to nine rays.
1 genus with 2 species confined to fresh waters of North America north of Mexico. The common name for this family was assigned to it by early naturalists, who thought it to be an intermediate form in the evolution from trouts to perches. These fishes have pelvic fins with eight to nine rays. The pectoral fin extends beyond the pelvic fin insertion. One to three spines precede each dorsal and anal fin. Trout perches have an adipose fin and small ctenoid scales.
1 species confined to fresh waters of eastern North America. Pirate perches are unusual in that, as they mature, the anus moves forward from just in front of the anal fin in juveniles to a point anterior to the pelvic girdle in the throat region in adults.
This order consists of a single family: 5 genera and 6 species confined to fresh waters of North America. These fishes are found in caves, springs, and swamps of the east-central and eastern United States. Their evolution exhibits the transition from surface water to springs to subterranean habitats; they share morphological adaptations, including blindness or small rudimentary eyes and exposed sensory papillae in rows on the head and body. The species found in the surface water of swamps and those adapted to springs have rudimentary eyes and sensory papillae on the head and are pigmented (see below, left); those adapted to habitats in, or around the entrance to, caves are blind, have numerous sensory papillae on the head, body, and tail, and lack pigmentation (see below, right). Other interesting cave adaptations include a decrease in metabolic rate and a reproductive strategy in which the few large eggs are held in the gill chamber of the female after being fertilized and during the early stages of development. All family members have a single dorsal fin either lacking spines or with one or two spines, and seven to 12 rays. The anal fin is either spineless or has one or two spines, and has seven to 11 rays. Small embedded cycloid scales are present on the body, but absent on the head. In adults, the anus is situated anteriorly near the junction of the gill membranes.
Order Ophidiiformes
This order contains five families; in North America, three families are known to occur in inshore waters, and two are found in deeper waters. There are also a number of unnamed species in North America and throughout the world. Previously considered part of the broad order Gadiformes, these benthic fishes are slender and elongate, with bodies tapering to pointed tips. The bases of the dorsal and anal fins are long, extending to the end of the body, where they either meet with each other or with the caudal fin. When present, the pelvic fins are inserted at the level of the preopercle, sometimes even forward to beneath the eye; each pelvic fin has one or two elongate rays, and occasionally a spine. There are paired nostrils on each side. Some species are unscaled. The families Carapidae (pearlfishes) and Ophidiidae (cusk-eels) are oviparous and lack external copulatory organs. The family Bythitidae (viviparous brotulas), with at least six species in North America (plus many still unnamed), is viviparous, and includes several freshwater species in the Bahamas, Cuba, and Mexico. A pelagic vexillifer larval stage is present in the Carapidae, but is absent in the other families.
7 genera and 32 species worldwide; 2 genera and 2 species in North America. Found in tropical seas, these small, very slender, unscaled fishes have long bodies tapering to pointed tips. Pectoral fins are sometimes absent. The long dorsal and anal fins meet at the tip of the body; the tail usually disappears as the fish develops. The rays of the anal fin are longer than those of the dorsal fin. The anus and anal fin origin are far forward in adults, located behind the head and usually beneath the pectoral fins. The gill openings are wide and extend far forward, and there are six to seven branchiostegal rays. There are teeth in the jaws and on the bones in the roof of the mouth, with prominent fangs sometimes present on the premaxilla. The opercle is spineless. Some species are inquiline (living within the bodies of various marine invertebrates without doing any harm to the host). Pearlfishes pass through two distinct larval stages: a pelagic vexillifer stage, which looks like a plant stem with small leaves, and then a demersal tenuis stage, which is extremely elongate and ribbon-like.
46 genera and about 209 species worldwide; 7 genera and 18 species in North America, plus at least 9 species in Mexican waters. Cusk-eels are found in tropical to temperate waters. These bottom-dwelling fishes live in burrows or rocks and occur over an extraordinarily wide depth range, from the shoreline to the greatest depth at which any fish species has been collected, almost 27,560’ (8,400 m). Some species are spotted, but most lack distinctive markings; all are scaled. Most cusk-eels have two elongate rays in each pelvic fin, located below the opercle or under the eye. Some species have one or more spines on the opercle, and some have a spine underneath the skin near the snout tip. The dorsal fin rays are usually equal to or longer than the anal fin rays. The anus and anal fin origin are usually behind the pectoral fin tip. A supramaxillary bone is present. Males lack an external copulatory organ. Cusk-eel larvae do not go through a vexillifer larval stage, in contrast to the related pearlfishes (family Carapidae).
Order Myctophiformes
This order contains only two families, the Myctophidae, or lanternfishes, with about 235 species, and the Neoscopelidae, or blackchins, with five or six species. Both families are widespread in deep ocean waters. Their diagnostic characteristics are technical features of the gill arches that are beyond the scope of this field guide.Order Gadiformes
This order contains 12 families, seven of which are found in North American waters. Members of this order occur in cold-temperate to arctic waters of the Northern Hemisphere. Most are marine; one species is primarily marine but also occurs in isolated inland waters, and another species is confined to fresh water. These fishes have elongate tapering bodies and spineless fins. When present, the pelvic fins are located below or in front of the pectoral fins; each pelvic fin has up to 11 rays. The dorsal and anal fins are long, and the dorsal fin is often deeply divided into segments. The maxilla is not united with the edge of the upper jaw, and in some species the mouth is protractile. There are six to eight branchiostegal rays. Most species have cycloid scales. A swim bladder is usually present, without a pneumatic duct. Classification of this order has recently undergone many changes. One major group was placed in its own order, the Ophidiiformes; several groups formerly included in the family Gadidae have been recognized as separate families, including the phycid hakes (Phycidae) and the merlucciid hakes (Merlucciidae).
5 genera and 27 species worldwide; 3 genera and 9 species in North America (all Atlantic). Phycid hakes have pelvic fins with moderately to greatly elongate rays. The dorsal fin is separated into two or three segments; when divided into two segments, the first has eight to 13 rays and the second has 43 to 68 rays. All phycid hakes have chin barbels; some also have barbels on the snout (absent in North American species).
1 genus with 13 species worldwide; 3 species in North America (2 Atlantic, 1 Pacific). These fishes are found at mid-depths in northern and southern temperate regions of the world. Each pelvic fin has seven rays. The dorsal fin is divided into two segments; the first segment has eight to 13 rays, and the second deeply notched segment has 34 to 46 rays. The anal fin is notched, with 35 to 46 rays. The caudal fin is separate from the dorsal and anal fins; it is either squared at the tip or is slightly notched. Members of this family have tiny cycloid scales. The anus and urogenital opening are close together. The long terminal mouth has a black interior and long teeth; vomer teeth are present, but palatine teeth are absent. There are seven branchiostegal rays. Unlike phycid hakes (family Phycidae), merlucciid hakes do not have chin barbels.
15 genera and about 30 species worldwide; 12 genera and 16 species in North America (7 Atlantic, 4 Pacific, 4 shared, 1 fresh water). These fishes are confined to cold-temperate or arctic waters of the Northern Hemisphere; one species is restricted to fresh water, and at least one has occasional freshwater, or even landlocked, populations. Cods have spineless fins. The long dorsal and anal fins are both sometimes deeply divided, the dorsal fin into as many as three segments and the anal fin sometimes into two segments. Some species have a barbel on the chin. The scales are small and cycloid. Valuable as food, most cods are harvested commercially and sold fresh, dried, or salted. Historically, they were important as a major trading item. Some species are sought by anglers. The eggs of cods are usually free-floating. Because of recent changes in classification, the family is now much reduced in size.
This order consists of a single family: 19 genera and more than 69 species worldwide; 2 genera and 6 species in North America (4 Atlantic, 2 Pacific), plus 2 genera and 12 species confined to Mexican waters (including 1 restricted to fresh water). These fishes occur mostly in tropical to temperate seas; several species live permanently in fresh water. Toadfishes live on the bottom, mostly in bays, lagoons, and coastal waters along continental shelves. A few species are found around coral reefs, and one occurs to depths of 1,200’ (366 m). Toadfishes are small to medium, slow-moving, carnivorous fishes. Most are drab brown and variously blotched and mottled, but a few are strikingly marked and colorful. Members of the genus Porichthys have rows of photophores on the underside of the head and body. All have a moderately broad and flat head, with eyes near the top of the head and directed upward. The dorsal fin is separated into two segments, and the first segment has two or three low stout spines. In two tropical genera, the opercular spine and two dorsal fin spines are hollow and serve to conduct poison from underlying venom glands. The anal and second dorsal fins are low and long, with at least 15 and 18 fin rays, respectively. The pelvic fins are small and situated under the throat. The small caudal fin is usually rounded. When present, the scales are small and cycloid. Toadfishes have at least one lateral line. There is no larval stage; the young are miniature replicas of the adults.
Order Lophiiformes
This order contains 16 families, six of which are found in North America. A number of additional species occur in deeper waters offshore. All species are marine; a high percentage are restricted to deep water, some living at mid-depths and most on the bottom. The bodies of these fishes are usually strongly compressed, either laterally or dorso-ventrally. The small gill opening on each side is situated partly in front of the pectoral fin base. The pelvic fins are well in front of the pectoral fins, which sometimes function as “legs” for locomotion. The first ray of the spiny dorsal fin is often greatly elongate and modified into a “fishing pole” (the illicium) of varying length; the spine tip contains a fleshy appendage (the esca) that functions as a "lure." In some deep-sea families the male is tiny and permanently attached to the body of the female. The highly modified morphology and unusual life history of some families make the lophiiform fishes among the most bizarre of all fish groups.
4 genera and 25 species worldwide; 2 genera and 5 species in North America (3 Atlantic, 2 Pacific). Found in tropical to cold-temperate seas throughout the world, members of this family have broad, rounded, flat heads and tapering bodies, squarish pectoral fins, and wide superior mouths that are equipped with many thin sharp teeth. The dorsal fin is divided into two segments; the soft-rayed segment is long and squarish, and the spiny segment is separated into several free spines that extend forward to the front of the head. The foremost dorsal fin spine, located just behind the upper lip, is modified to form a “fishing pole,” complete with a fleshy “lure” at the tip; this structure attracts the smaller fishes that are part of a goosefish's diet. Goosefish flesh has an excellent flavor and is sold as a delicacy in Japan, Europe, and North America.
14 genera and 43 species worldwide; 2 genera and 7 species in North America (6 Atlantic, 1 Pacific). Found in tropical and warm-temperate seas, these small fishes have globular, slightly to moderately compressed bodies. They are poor swimmers; their coloration changes to match their environment, and they depend on this camouflage for concealment from predators. The skin is either prickly or smooth and often has fleshy flaps. The mouth is strongly superior and oblique. The pectoral fins are limb-like. The first dorsal fin spine, located near the snout tip, is separated from the rest of the long dorsal fin and modified into a “fishing pole” with a “lure” at its tip. Frogfishes feed by waiting in ambush, or by enticing other fishes. The “lure” is wiggled to mimic a live animal, attracting potential prey. Faster than the eye can follow, the frogfish gulps the unsuspecting victim.
9 genera and 62 species worldwide; 4 genera and 11 species in North America (10 Atlantic, 1 Pacific). Batfishes occur mostly in tropical seas over open rubble or mud-clay bottoms from the shore to depths of 6,000’ (1,830 m). They have disk-shaped, ventrally flat bodies and small ventral mouths. The snout extends in front of the eyes, and varies from short and blunt to long and pointed, depending on a combination of size and age of individual and the species involved. The gill openings are reduced to small holes behind the pectoral fins. The pelvic fins are well in front of the pectoral fins; these paired fins are limb-like, with the pectoral fins functioning as legs for “walking” along the bottom. The short first dorsal fin spine extends beyond and below the snout; this spine is modi fied to form a short “fishing pole,” and is usually retracted into a groove beneath the snout. Batfishes feed on snails, clams, small fishes, and crustaceans, but it is not known which food, if any, is attracted to the modified first dorsal fin spine. The scales are highly modified to form bucklers, which are especially large and well developed on the back.
This order consists of a single family: about 17 genera and at least 66 species worldwide; 2 genera and 7 species in North America, plus 2 genera and 5 species confined to Mexican waters. Mullets live primarily in coastal waters and in estuaries in warm-temperate and tropical regions throughout the world. Early development is in the ocean; adults of some species enter fresh water and may ascend rivers for considerable distances, and others spend their entire adult life in fresh water. These fast-swimming fishes often jump clear of the surface. They range in size from small to fairly large, reaching lengths of 3’ (91 cm). They have elongate bodies that are almost cylindrical near the head, but become compressed posteriorly. The snout is blunt, the mouth is small and wide, and the premaxilla is protractile. The adipose eyelid is sometimes well developed. The pelvic fins are located about midway between the middle of the abdomen and the pectoral fin base. The pectoral fins are inserted above the axis of the body. The dorsal fins are well separated, the first consisting of four spines. The scales are usually described as cycloid; however, they actually change from a cycloid to a ctenoid condition in adults of many species. The lateral line is very faint or absent. This group was previously placed in the order Perciformes, and shares a number of characteristics generally associated with that order, such as spiny pelvic, dorsal, and anal fins, abdominal pelvic fins, and scales either cycloid or ctenoid.
Order Atheriniformes
This order contains eight families, two of which occur in North America north of Mexico. Members of this order are morphologically diverse and are distributed worldwide in virtually all tropical and temperate marine, brackish, and freshwater environments. The pelvic fins are abdominal, subabdominal, or thoracic. There are usually two dorsal fins; when present, the first consists of weak flexible spines. The anal fin usually has a single spine preceding the rays. The lateral line is absent or very faint, and the pores are not joined by tubes. The nostril openings are paired. Classification of the order has undergone radical changes, with many families now included in the orders Beloniformes and Cyprinodontiformes. One indication of the close relationship among these orders is the evolution of live-bearing species and the ability of the eggs in certain genera to completely develop in a dry environment.
13 genera and about 74 species worldwide; 6 genera and 13 species in North America, plus 6 genera and 44 species confined to Mexico, mostly in fresh water. These fishes, found in temperate and tropical marine, brackish, or fresh waters, are mostly small, delicate, elongate, and slightly compressed. All have a silvery lateral stripe on each side extending from the pectoral fin to the caudal fin. The mouth is terminal and oblique. The two dorsal fins are well separated; the first consists of a few weak spines. The pelvic, second dorsal, and anal fins each have a single spine preceding the rays. The scales are large and cycloid, and the lateral line, when present, is placed low on the side. This family was formerly included in the family Atherinidae (now known as the Old World silversides); external characteristics are virtually identical in both families.
Order Beloniformes
This order contains five families, four of which are found in North America. Many species are confined to fresh water or weak brackish water. These fishes have elongate bodies; the back is not elevated. The jaws are very elongate in some groups; the upper jaw is not protractile. The pelvic fins are usually abdominal, sometimes subabdominal; the pectoral fins are usually high on the body. The dorsal and anal fins are far back on the body. The lower lobe of the caudal fin has more rays than the upper lobe. Reproduction in these fishes is usually oviparous, occasionally viviparous.
10 genera and 32 species worldwide; 4 genera and 8 species in North America. Needlefishes are found in tropical to temperate waters; most species are marine, but some occasionally occur in fresh water. They have very elongate bodies that are either cylindrical or compressed. The jaws are usually very long, beak-like, and armed with numerous sharp teeth. The spineless fins are similar to those of flyingfishes (family Exocoetidae) and halfbeaks (family Hemiramphidae). The pelvic fins are abdominal; the dorsal and anal fins are far back on the body and similar in size and shape; and the lower lobe of the caudal fin is longer than the upper. Needlefishes are found near the surface and skitter over the water. They are predators that feed primarily on small fishes. These fishes are often called gars or saltwater gars because of their physical and behavioral similarities to freshwater gars (family Lepisosteidae), but the two families are not closely related.
7-8 genera and about 53 species worldwide; 6 genera and 14 species in North America (10 Atlantic, 3 Pacific, 1 shared), plus 1 genus and 13 species confined to Mexican waters. Flyingfishes are found in tropical to temperate seas. They have nearly cylindrical bodies that are bluish above, shading to silvery on the sides, and white on the belly. All fins are spineless. The pelvic fins are abdominal, sometimes very elongate and extending beyond the anus. The pectoral fins are located high on the sides and are usually greatly enlarged (only slightly enlarged in the genus Oxyporhamphus). The dorsal and anal fins are placed far back on the body. The lower lobe of the caudal fin is longer than the upper. The elongate caudal fin lobe propels the fish out of the water, and the enlarged pectoral fins function as 'wings' as the fish glides through the air (although actual flapping of the fins does not occur). The scales are cycloid, and the lateral line pores follow the ventral contour of the body. Young flyingfishes have a very elongate lower jaw, which regresses during development and is equal in length to the upper jaw in adults. In the closely related halfbeaks (family Hemiramphidae), the elongate lower jaw in most species is retained throughout life. Flyingfishes live near the surface of open oceans, where they are often abundant, but the young may enter bays, and adults approach shores of oceanic islands to spawn. They are commercially important food fishes in some areas in the Greater Antilles.
12 genera and about 85 species worldwide; 4 genera and 9 species in North America (5 Atlantic, 3 Pacific, 1 shared). These fishes are found in tropical to temperate waters; four genera occur in fresh water. Until recently, they were included in the closely related flyingfish family (Exocoetidae). They have similar cylindrical bodies that are bluish above, shading to silvery on the sides, and white on the belly. The upper jaw is usually much shorter than the lower jaw throughout life (in flyingfishes, this is true only in young). All fins are spineless. The pelvic fins are abdominal, and the pectoral fins are located high on the sides; in contrast to the flyingfishes, the paired fins are not enlarged. The dorsal and anal fins are placed far back on the body. The lower lobe of the caudal fin is elongate in some species. Some halfbeaks have internal fertilization and viviparous reproduction (none in North America).
Order Cyprinodontiformes
This order contains eight families, seven of which are found in North America. Members of this order inhabit marine, estuarine, and fresh waters. They are characterized by a symmetrical caudal fin, well-developed sensory canal pores on the head, pitted scales, and the absence of a lateral line. They exhibit marked sexual dimorphism, with brightly colored males.
4 genera and about 48 species worldwide; 4 genera and 36 species in North America, plus 3 species in Mexico. These small fishes occur in fresh, brackish, and coastal marine waters; they spend most of their time near the surface of the water, where they are easily observed. Topminnows have teeth, and the single dorsal fin is far back on the body. The males lack external reproductive organs, and the females lay eggs; both characteristics are important in distinguishing topminnows from the closely related livebearers (family Poeciliidae).
30 genera and about 300 species world- wide; 4 genera and 13 species native to North America north of Mexico, plus 8 genera and 77 species in Mexico. Mem- bers of this family are found in North America, Central America, South America, and Africa; they occur in a variety of habitats in fresh, brackish, and salt waters. Livebearers are elongate, small-bodied fishes, usually reaching lengths of less than 8” (20 cm), with a small upturned mouth. They have a single dorsal fin placed near the mid-body. There are 35 or fewer rows of scales in the lateral series. Unlike the closely related topminnows (family Fundulidae), these fishes give birth to live young after internal fertilization. The male transmits packets of sperm into the female by a complex copulatory organ (the gonipodium) formed from the first few rays of the anal fin. The sperm packets may be held by the female for up to 10 months and used to fertilize several broods.
19 genera and 40 species confined to fresh waters of Nevada and Mexico. Goodeids from the two regions differ in morphology and reproductive biology and are placed in different subfamilies. The subfamily Empetrichthyinae (2 genera and 4 species) is found only in desert springs in southern Nevada. They lack pelvic fins; the dorsal fin, which has 10 to 12 rays, and the anal fin are both located on the posterior part of the body. There are 25 to 33 scales in the lateral series. Members of this subfamily are small, reaching a maximum length of 3 1/2" (9 cm), and the eggs are deposited in vegetation and fertilized externally. The subfamily Goodeinae (17 genera and 36 species) is found only in west-central Mexico. They are morphologically similar to the Empetrichthyinae, except males have short crowded anterior anal fin rays that are separated from the remainder of the fin by a deep notch; this structure is used by the males to accomplish internal fertilization. The young are born live; embryos and newborns typically have ribbon-like extensions on the anal region, which are associated with nutrition and respiration during development. Members of this subfamily often reach a length of 8” (20 cm). The differences between the subfamilies reflect the long period of geographic isolation between the two groups.
9 genera and about 100 species worldwide; 3 genera and 14 species in North America, plus 2 genera and 23 species in Mexico. Pupfishes are found in fresh and brackish waters and coastal marine habitats in North America, parts of northern South America, northern Africa, and the Mediterranean region. They have relatively short deep bodies with upturned mouths. Some lack pelvic fins (present in most North American species), and all have a single dorsal fin. These fishes tolerate extreme environmental conditions, with some species inhabiting waters ranging from near freezing to 113 degrees fahrenheit (45 degrees celsius), saline waters more than four times saltier than seawater, or waters with the lowest levels of dissolved oxygen known for any gill-breathing fish.
Order Beryciformes
This order contains seven families, three of which occur in North American Atlantic inshore waters. Other families are found in deeper waters offshore. Many of these fishes are bottom dwellers. Most have large eyes, and one family, the Anomalopidae (flashlight fishes), is bioluminescent. Members of this order have a relatively deep body. The pelvic, dorsal, and anal fins each have a single strong spine preceding the rays. Each pelvic fin has more than five rays, and is either thoracic or placed beneath the middle of the pectoral fin. The caudal fin has 18 to 19 rays. Several families formerly included in this group have been placed in different orders.
8 genera and about 65 species worldwide; 7 genera and 11 species in North America, plus 5 species confined to Mexican waters. These relatively deep-backed, compressed fishes are usually colored various shades of red. They have large eyes, a large ter minal mouth, and hard spiny scales. The bones around the eye and opercle are serrate. Most species have a large spine at the angle of the preopercle and another on the upper edge of the opercle; these spines can inflict wounds. Each pelvic fin has a single spine preceding seven rays. The dorsal fin is long-based; the well-developed spiny segment has 10 to 12 spines and is nearly separated from the much shorter soft segment. The anal fin has four spines, the third one greatly enlarged. Most squirrelfishes live in shallow tropical coral reefs; some occur over sand or mud to depths of 900’ (275 m) or more. They are most active at night.
Order Gasterosteiformes
This order contains 11 families, six of which occur in North America. Members of this order are found in tropical to cold-temperate marine and fresh waters throughout the world. Most species are marine, but nearly one-fourth occur in either fresh or brackish waters. Many families are highly modified morphologically. These fishes usually have a very elongate, tube-like snout with a tiny mouth at the end. The body is usually pencil-like, often partially or completely covered with bony plates, and sometimes has long fleshy appendages and a prehensile tail. A brood pouch may be present on the belly in males. Classification of the order is unsettled, with some families proposed for addition.
2 genera and 2 species worldwide; 1 species in North America. These fishes are confined to the cold-temperate waters of the North Pacific Ocean from Japan and Korea to California. The body is elongate, with a series of 24 to 26 very short and isolated dorsal fin spines followed by a soft dorsal fin with about 20 rays; the soft dorsal fin is situated directly above the anal fin on the posterior one-third of the body. The small pelvic fins are located beneath the pectoral fins. The sides of the body are covered with thin bony plates. The snout is tube-like (hence the family's common name), with a terminal, moderately prominent mouth. Tubesnouts were previously included in the stickleback family (Gasterosteidae).
5 genera and about 7 species worldwide; 4 genera and 5 species in North America. Sticklebacks are widely distributed in the Northern Hemisphere in fresh, brackish, and salt waters. These small fishes are characterized by the presence of three to 16 isolated dorsal fin spines followed by a soft dorsal fin with 14 to 16 rays. They have a fusiform body with a very long slender caudal peduncle. They are unscaled, but the sides are often covered with bony plates. Sticklebacks are widely known for their complex mating behavior and nest-building activity.
52 genera and about 215 species (190 pipefishes, 25 seahorses) worldwide; 9 genera and 28 species (24 pipefishes, 4 seahorses) in North America (21 At- lantic, 7 Pacific), plus 1 genus and 5 species in Mexican waters. Members of this family are found in tropical to cold- t emperate waters. All North American species are marine, with two pipefish species also occurring in fresh water; one of these may have some permanent freshwater populations. They are small atypical fishes, with bodies encased in bony rings perpendicular to several discontinuous longitudinal ridges running along the sides of the body. Pipefishes have a straight body, and seahorses have a curved prehensile tail; a few genera are morphologically intermediate and appear to bridge the gap between the two groups. Characteristics important in identification include the number of bony rings on the body, particularly the total number and relative numbers before and behind the anal fin; length and position of longitudinal ridges along the sides of the body; snout length; position of the dorsal fin relative to the body rings; number of dorsal fin rays; presence or absence of an anal fin; and length, position, and morphology of the brood pouch on the belly of the male.
1 genus with 3 species worldwide; 1 species in North America. These unmistakable fishes are found in tropical seas. They are similar to the pipefishes and seahorses (family Syngnathidae) and the cornetfishes (Fistulariidae) in that they have a very long body with the mouth at the end of a tubular snout. They differ by having a chin barbel; a series of seven to 12 isolated dorsal fin spines, together resembling a small sail, followed by a short soft dorsal fin; the anal fin placed below, and about equal in size and shape to, the soft dorsal fin; and the pelvic fins located below the middle dorsal fin spines.
1 genus with 4 species worldwide; 3 species in North America (2 Atlantic, 1 Pacific), plus 1 species confined to Mexican waters. These fishes are found in subtropical coastal waters. They are more slender than trumpetfishes (family Aulostomidae) and have depressed, mostly unscaled bodies (some species are completely unscaled). The head is long, and the mouth is at the end of a tubular snout. They do not have chin barbels. The dorsal and anal fins are spineless, short-based, posteriorly placed, and similar in size and shape. The small caudal fin is forked, with the middle two rays forming a long filament.
Order Scorpaeniformes
This order contains 24 families, 12 of which occur in North America. Nearly all species are marine, the exception being about 52 species in the sculpin family (Cottidae), which are confined to fresh water in cool-temperate regions of North America, Asia, and Europe. The head and body usually have spines and sometimes bony plates. The pelvic, pectoral, dorsal, and anal fins often have well-developed spines. The pectoral fins are usually rounded; the caudal fin is also usually rounded, rarely forked. This group was previously included in the order Perciformes, and the relationships among these fishes are not completely resolved.
At least 56 genera and about 388 species worldwide; 8 genera and 92 species in North America (24 Atlantic, 68 Pacific). These fishes, found in tropical to cold-temperate waters throughout the world, have fusiform compressed bodies. They have ridges and spines on the head, including coronal spines (those located where the top of the head and the nape come together); in addition, there are usually five spines on the preopercle and two on the opercle. All members of the family have a bone beneath the eye that extends across the cheek. They have a single dorsal fin, often notched, with 11 to 17 spines and eight to 18 rays. The anal fin has one to three spines and three to nine rays. The pelvic, dorsal, and anal fin spines often contain venom glands that may cause very painful wounds. When present, the scales are ctenoid or cycloid. Fertilization is internal, and some species lay eggs. Many of the species in the genus Sebastes are difficult to distinguish from one another; they all have palatine teeth and a dorsal fin with 12 to 15 (usually 13) spines and nine to 16 rays, and all are ovoviviparous. Those family members found in the North Pacific are often known as rockfishes.
10 genera and about 70 species worldwide; 2 genera and 17 species in North America (15 Atlantic, 2 Pacific), plus 5 species confined to Mexican Pacific waters. Searobins are small to medium, variably colored fishes that live on the bottom. They are easily recognized by their large heads with many ridges and spines; broad flat snouts and equally broad, terminal or slightly inferior mouths; and usually large, wing-like, often brightly colored pectoral fins with the first three rays free and detached from the rest of the fin. The free pectoral fin rays are used in "walking" along the bottom and as sense organs for probing the bottom in search of food. The spiny dorsal fin is triangular, with 10 spines in the genus Prionotus and 11 in Bellator. The soft dorsal fin and the anal fins are long and continuous. The body is covered with small, firmly set ctenoid scales. These fishes inhabit continental and insular shelves of tropical and temperate seas to depths of about 570’ (174 m). Until recently, the armored gurnards (now classified as the family Peristediidae), which occur in deeper water than searobins, were considered a subfamily of the Triglidae; they have two free pectoral fin rays, two forward-projecting spines on the snout, long fleshy barbels on the lower jaw, and scales modified into four rows of bony scutes.
2 genera and 2 species worldwide; both species in North America. Members of this family are confined to temperate waters of the North Pacific. Sablefishes have elongate, fusiform, slightly compressed bodies. They lack spines, ridges, and cirri on the head. The dorsal fin is divided; the spiny first segment is rounded, and the soft second segment is smaller and triangular. The small triangular anal fin has three or fewer weak spines (sometimes absent) and 11 to 23 rays. The caudal fin is truncate or indented. The scales are ctenoid, and a lateral line is present.
5 genera and 11 species worldwide; 5 genera and 9 species in North America. Restricted to the North Pacific, the colorful greenlings have elongate, slender, slightly compressed bodies with cirri but no ridges or spines on the head. The snout is sharp, blunt, or rounded. The long dorsal fin usually has a notch separating the 15 to 27 spines from the 11 to 26 rays. The long anal fin has four or fewer spines, which are sometimes longer than one-third of the body length. The caudal fin is truncate or forked. These fishes have one to five lateral lines, and the scales are either ctenoid or cycloid. Combfishes (genus Zaniolepis), which have the unique ability of contorting their bodies into a U-shape, are sometimes considered a separate family.
1 species worldwide. Grunt sculpins are found in the North Pacific from Japan to Alaska and south to southern California. These distinctive fishes have a very long head, about half as long as the length of the body from the tip of the snout to the base of the tail, and an elongate snout. There are six branchiostegal rays, and all fin rays are unbranched. This family was formerly included in the sculpin family (Cottidae).
About 70 genera and about 300 species worldwide; 34 genera and 108 species in North America (5 Atlantic, 69 Pacific, 8 shared, 26 freshwater), plus a few species in deeper offshore waters. These fishes are mostly marine, but some (nearly all in the genus Cottus) are strictly freshwater. The family is restricted to cold-temperate and arctic waters, with the majority of marine species concentrated in the North Pacific; they frequently occur in rocky intertidal zones. Most sculpins have a large head and mouth, and an elongate tapering body partly covered with scales or prickles; a few are completely unscaled. The large eyes are placed high on the head, and there are usually one to five well-developed preopercular spines. These fishes have a lateral line. Each pelvic fin has a single spine and two to five rays. The pectoral fins are broad and fan-like. Most species have a deeply notched or divided dorsal fin. The soft-rayed anal fin is usually about as long as the second dorsal fin. Fourteen North American marine species recently included in this family are now placed in the closely related families Rhamphocottidae (grunt sculpins), Psychrolutidae (fathead sculpins), and Hemitripteridae (searavens).
3 genera and 8 species worldwide; 3 genera and 7 species in North America (1 Atlantic, 6 Pacific). The characteristics distinguishing this family from other closely related families in the order Scorpaeniformes mostly involve details of the internal anatomy. The one prominent external feature that sets apart the searavens is the presence of minute spines covering the body.
20 genera and 44 species worldwide; 15 genera and 27 species in North America (24 Pacific, 3 Atlantic and Pacific). These fishes are restricted to cold temperate to arctic marine waters. One species is confined to the eastern North Atlantic, and another four species are restricted to the area around the southern tip of South America. Most poachers have elongate slender bodies tapering to small caudal fins and dorsal fins divided into two distinct segments. When separate, the first dorsal fin is spiny and the second is soft-rayed. The pelvic fins have one spine and two rays and are situated below the pectoral fins. There are no spines in the anal fin. A few species have cirri, usually on the lower jaw. Poachers are sometimes confused with juvenile sturgeons (order Acipenseriformes), since both groups have scales modified as bony plates.
7 genera and 28 species worldwide; 5 genera and 11 species in North America (7 Pacific, 2 Atlantic, 2 shared). Lumpfishes are found in cold-temperate to arctic waters of the Northern Hemisphere. They have a globose body usually covered with tubercles (one genus has a naked body). When present, the pelvic fins are modified into sucking disk. The dorsal fin is usually divided into two short segments, the first with four to eight spines (concealed beneath the skin in some species),the second with eight to 13 rays; it is never joined to the caudal fin. The anal fin is short, with seven to 13 rays. This family formerly included the snailfishes (family Liparidae).
About 19 genera and at least 195 species worldwide; 6 genera and 36 species in North America (7 Atlantic, 26 Pacific, 3 shared). Most species occur in cold temperate to arctic waters of the Northern Hemisphere, but at least 45 species are found in the Antartic region and perhaps some in deep waters in intervening tropical latitudes. These fishes occur over a wide depth range, from the shoreline to depths of more than 23,100' (7,046 m). the body is elongated and unscaled (some species have small prickles), and sometimes tadpole-like in appearance. Snailfishes have either single or paired nostrils, and the skin is very soft and flabby. When present, the pelvic fins are joined together as an adhesive disk; this disk is absent in at least 45 species(including three in North America). The dorsal and anal fins are long and continuous (or nearly so) with the caudal fin. Members of this family reach a maximum length of about 20' (51 cm). They were formerly including in the lumpfish family (Cyclopteridae).
This order contains a single family: 2 genera and 7 species worldwide; 1 Species in North America. This group, which at various times has been allied with either the orders Syngnathiformes or Scorpaeniformes, is now regarded as a separate orders, closely related to the Scorpaeniformes. These bottom-dwelling fishes are found in tropical to temperate seas, absent only from the eastern Pacific; the sole North American representative of the order is widespread in the tropical and warm-tempereate areas of the Atlantic. The elongated body is squarish in cross section, tapers posteriorly, and is covered with scute-like scales. Thick bones on the top of the large blunt head are fused into a bony shield, and there is a large, spine-like apparatus on each side of the nape. The mouth is small and low. The eyes are relatively large, and there is a pointed, extremely long preopercular spine on each side of the head. The pelvic fins are thoracic, each with one spine and four rays. Each pectoral fin is separated into two segments, the upper part relatively short and the lower part greatly expanded and reaching almost to the caudal fin base. The dorsal fin is also separated into two segments; the first one or two spines of the first part are free, not connected to the rest of the fin. The caudal fin is emarginated, and there are two sharp keels on each side of the caudal peduncle.
Order Perciformes
This is the largest order of bony fishes, which as presently constituted includes 18 suborders and 148 families; 13 suborders and 81 families are found in North America, plus at least 200 species in Mexican waters. Classification of the order is unsettled; there have been many recent changes, and others are expected in the future. These typical spiny-rayed fishes occur in marine and fresh waters. The pelvic fins usually consist of a single spine and five rays, and there are spines on the anterior parts of the dorsal and anal fins. The scales are typically ctenoid, and a lateral line is almost always present.
3 genera and 22 species worldwide; 1 genus with 4 species in marine and fresh waters of eastern North America, plus 8 species confined to Mexican Atlantic and Pacific waters. These rather large fishes have elongate compressed bodies with well-separated dorsal fins. The short-based anal fin has three spines, with the second spine enlarged. The lateral line extends to the caudal fin tip. The snout is pointed, the mouth is large, and the lower jaw projects well beyond the upper. Snooks inhabit tropical coastal waters, estuaries, and lagoons, and often enter fresh water.
1 genus with 4 species confined to North America. These fishes are found in fresh, brackish, and salt waters. They are characterized by the presence of one or two preopercular spines; two dorsal fins, deeply divided or separate, the first with eight to 10 spines and the second with one spine and 10 to 13 rays; an anal fin with three spines and nine to 12 rays; and a complete lateral line extending onto a forked caudal fin. Many temperate basses are important food and sport fishes. During the past few decades, fishery biologists have cultured hybrids of several species. The cross between a female White Bass (Morone chrysops) and a male Striped Bass (M. saxatilis) is known as Sunshine Bass; the reciprocal cross is called Palmetto Bass. Other names for hybrids between White Bass and Striped Bass are Wiper (or Wiper Bass) and White Rock Bass. The cross between a male Yellow Bass (M. mississippiensis) and a female Striped Bass is known as Paradise Bass. Crosses between White Perch (M. americana) and Striped Bass are called Virginia Bass and Maryland Bass. Of all these crosses, the most frequently stocked were Sunshine Bass and Palmetto Bass. However, with increased success in stocking Striped Bass in inland waters, the interest in releasing hybrids has declined in many states. Some of the hybrids are known to backcross with the parental species, which genetically contaminates the stock of the native species.
2 genera and 2 species worldwide; both species in North America (1 Atlantic, 1 Pacific). These very large fishes are widespread in the Atlantic and in the eastern and western North Pacific (but absent from intervening boreal waters) and occur disjunctly in temperate regions of the South Pacific and Indian Oceans. They are very similar externally to members of other generalized perciform families; this has led to past uncertainty in classification, and the species at various times have been included in the sea bass family (Serranidae) or the temperate perch family (Percichthyidae). One of the most distinctive external features is the dorsal fin ray count (nine to 12), which is lower than for other perciform fishes of similar appearance and size.
About 62 genera and 449 species worldwide; 21 genera and 80 species in North America (66 Atlantic, 14 Pacific), plus 28 species confined to Mexican waters. As the common name implies, all sea basses are marine. Since these are generalized perciform fishes, our understanding of interrelationships within the family is still not completely resolved. Some groups formerly placed in other families, including the soapfishes (formerly the Grammistidae), are now included in the Serranidae; others have been removed and placed in other families, such as the cardinalfishes (Apogonidae). Some, including the temperate basses and the wreckfishes, have been accorded family status (Moronidae and Polyprionidae, respectively). As now constituted, the sea basses can be characterized as perch-like fishes with a usually slightly notched dorsal fin and an anal fin with usually three to five spines. The mouth is generally large, with a broad exposed maxilla and teeth on the jaws and the roof of the mouth. The upper edge of the opercle is free and usually has three flat spines. The lateral line is complete and extends to the caudal fin base. Sizes of species within this family vary tremendously; some are less than an inch long and weigh only a few ounces, while others reach a length of 8’ (2.4 m) and a weight of at least 700 lb (318 kg). Many sea basses change color patterns during the transformation from juvenile to adult. Coloration may also alter as the fish moves around and as the light intensity changes, so that red colors become more prominent as the light dims. Sex reversal has been documented in a number of species; typically, younger individuals are females, changing into males with increasing age. The common name grouper is often applied to large species in the closely related genera Mycteroperca and Epinephelus and in other related genera, including Cephalopholis.
3 genera and about 90 species (some unnamed) worldwide; 2 genera and 8 species in North America, plus 8 species confined to Mexican waters. Jawfishes are found in tropical seas; the North American species all occur in the Atlantic. These fishes dwell in burrows, usually with only their heads exposed, and they use their large mouths for excavation. Males often have an extremely well-developed maxilla. The body is covered with cycloid scales, but the head is unscaled. The pectoral fins are located on the mid-side of the body, and the pelvic fins are slightly in front of the pectoral fins. Each pelvic fin has a single spine and five rays. The dorsal fin is of even height throughout, without an obvious notch between the spiny and soft segments; there are nine to 12 dorsal fin spines. The low anal fin is also even throughout; it has three spines and is about half the length of the dorsal fin. Both the dorsal and anal fins terminate at the same level, and are not connected to the rounded or lanceolate caudal fin. Jawfishes have a high lateral line, ending near the middle of the dorsal fin. These fishes reach lengths of about 4-16" (10-41 cm), depending upon the species. Males practice oral incubation.
7 genera and 31 species confined to North America. Sunfishes are one of the most widespread and popular groups of freshwater sport fishes in North America. The dorsal fin usually has a notch between the spiny and soft segments, and the anal fin has at least three spines. The caudal fin is usually forked. The gill membranes are usually separate. Most members of the genus Lepomis are characterized by a fleshy extension of the posterior edge of the opercle, which is referred to as the "ear flap" this structure is important in the identification of many species. Most sunfishes are nest builders; the nest is usually a depression 12-24" (30-61 cm) wide in shallow waters. The male excavates the nest using his anal and caudal fins, then guards the eggs after spawning. Except for a single species native to California, Sacramento Perch (Archoplites interruptus), sunfishes are indigenous to warm waters of North America east of the Rocky Mountains. However, as a result of their popularity with anglers, they have been introduced in other areas.
10 genera and more than 190 species worldwide; 6 genera and more than 180 species in North America, plus Ruffe (Gymnocephalus cernuus), an introduced European native now firmly established in the Great Lakes. Perches occur in the fresh waters of Eurasia and North America. The dorsal fin of these fishes is usually separated into two segments. The anal fin has one to two spines, and the second spine is not enlarged. The larger species, which reach lengths of 3’ (91 cm), are important sport fishes and have been widely introduced. The smaller species are among the most colorful fishes in the world. The four genera of darters, Percina, Ammocrypta, Crystallaria, and Etheostoma, together total more than 175 species and form one of the most diverse and colorful groups of North American freshwater fishes. With few exceptions, darters are found in North America east of the Continental Divide. Many have very restricted ranges and habitats. The collective common name describes their habit of “darting” about, using the tail and pectoral fins for locomotion. These movements are largely confined to the bottom, since most species lack a swim bladder. Percina (40 species) darters tend to be tan or brown with darker markings (any bright coloration is usually yellow or orange) and have two anal fin spines and a complete lateral line; males have specialized scales on the midline of the belly that are used during spawning to maintain their position and stimulate the female. Ammocrypta (six species) and Crystallaria (one species) darters are translucent with a faint yellow to orange wash, have a single anal fin spine and a complete lateral line, and males lack specialized scales on the midline of the belly. Etheostoma (130 species) darters have one to two anal fin spines and either a complete or incomplete lateral line, and males lack specialized scales on the belly. Males in the genus Etheostoma are usually brightly colored, as are some Percina males.
4 genera and 18 species worldwide; 3 genera and 5 species in North America (4 Atlantic, 1 Pacific), plus 1 species confined to Mexican Pacific waters. Bigeyes are found in tropical and temperate seas, and occur primarily in rock or coral reef habitats at depths of 6-420' (1.8-128 m) or more. These small to medium fishes are easily distinguished by their deep bodies and very large eyes. The mouth is large and quite oblique, and the lower jaw projects beyond the upper. The large pelvic fins are anteriorly placed and broadly joined to the body by a membrane. The dorsal fin has 10 spines and 11 to 15 rays. The anal fin has three spines and 10 to 16 rays. The caudal fin is emarginate to rounded. Bigeyes have ctenoid scales; the lateral line does not extend onto the caudal fin.
22 genera and at least 207 species worldwide; 3 genera and 20 species in North America, plus 5 species confined to Mexican waters. Cardinalfishes are found mostly in tropical seas, but a few Indo-Pacific species occur in fresh or brackish waters. These small fishes have large eyes and a large, terminal, oblique mouth. The dorsal fin is well separated into two segments, the first with six to eight spines and the second with a single spine and eight to 14 rays. The anal fin has two spines and eight to 18 rays. The lateral line does not extend onto the caudal fin. Members of this family are found primarily around tropical coral reefs, usually to depths of 150’ (46 m) or more. Because cardinalfishes are generalized perciform fishes, an accurate definition of the family has been difficult. Several groups once included in this family have been removed and placed in other families, most notably the Epigonidae (deepwater cardinalfishes) and Acropomatidae (temperate ocean basses).
5 genera and 39 species worldwide; 3 genera and 9 species in North America (6 Atlantic, 3 Pacific). These fishes reach lengths of 3'6" (1.1 m) and are found to depths of 300’ (92 m). The pelvic fins are thoracic in position, each with one spine and five rays. The very long dorsal and anal fins are continuous and composed mostly of rays. The caudal fin is emarginate to lunate. Tilefishes are elongate, varying from relatively robust to slender. Some species have a ridge or fleshy keel on the nape, and all have an opercular spine that varies from flat to sharp and strong. Some tilefishes are quite colorful. The larger species are important sport and commercial fishes.
2 genera and 3 species worldwide; 1 species in North America, plus 1 genus with 1 species in offshore waters to depths of 656-1,980' (200-604 m) off southern Florida. Bluefishes are found in tropical and temperate seas. Moderately large, robust, and relatively elongate, they superficially resemble certain species in the jack family (Carangidae). The dorsal fin is separated into two segments, the first with seven to eight low spines and the second with one spine and 13 to 28 rays. The anal fin has two to three spines and 12 to 27 rays. The second dorsal fin and the anal fin are covered with scales, and there is a black blotch at the base of each pectoral fin. Members of this family have a membranous flap over the subopercle.
1 species confined to eastern Pacific from California to Peru. Roosterfishes were previously placed in the jack family (Carangidae). Evidence suggests that these two families, together with the remoras (Echeneidae), cobias (Rachycentridae), and dolphinfishes (Coryphaenidae), form a natural lineage.
4 genera and 8 species worldwide; all found in North America (1 Atlantic, 7 Atlantic and Pacific). Seven of the eight species have worldwide distributions in tropical to warm-temperate seas. Remoras are instantly recognizable by the unique sucking disk on the top of the head; this oval disk is actually a modified spiny dorsal fin. Other than the disk, these fishes bear a close resemblance to cobias (family Rachycentridae) and are believed to have evolved from that family. Remoras are elongate fishes with superior mouths that open just anterior to the disk. They attach themselves to a variety of large marine fishes, mammals, and turtles, and sometimes to ships or other floating objects. They not only save energy and get a free ride, but feed on scraps of food left by their hosts. Species in the genus Echeneis are not host-specific, in contrast to the other genera.
1 species worldwide. These fishes are found nearly worldwide, absent only from the eastern Pacific. The depressed head, protruding lower jaw, and short isolated dorsal fin spines distinguish cobias from other fishes. Like their apparent relatives, the remoras (family Echeneidae), they linger around larger fishes for food scraps and protection.
About 32 genera and 140 species worldwide; 14 genera and 40 species in North America (25 Atlantic, 12 Pacific, 3 shared), plus 15 species confined to Mexican waters. Jacks are found in tropical to temperate seas. This is an extremely diverse family morphologically, ranging from streamlined, fast-swimming, torpedo-like fishes to slow-moving fishes with extraordinarily laterally compressed bodies. They have two dorsal fins. In some species, the dorsal and anal fin spines are persistent throughout the life of the fish; in others, the spines are evident only in the young, becoming extremely short and covered by skin as the fish increases in size. Some jacks have finlets behind the dorsal and anal fins. All have a forked caudal fin. Several genera have scutes, usually on the posterior one-third of the lateral line. These fishes usually form schools; their habitats range from inshore brackish waters to open seas. Some species are highly esteemed food and sport fishes, although a few have been linked to ciguatera poisoning.
21 genera and about 125 species worldwide; 5 genera and 21 species in North America (17 Atlantic, 4 Pacific), plus 7 species confined to Mexican waters. Snappers occur in tropical to warm-temperate seas throughout the world, living around reefs and on the outer continental shelf. They are oblong, moderately compressed fishes. Due to their generalized perciform characteristics, it is often difficult to identify them as members of the family Lutjanidae; in particular, snappers can be difficult to distinguish from species of the family Serranidae (sea basses). When the large terminal mouth is closed, the maxilla is nearly covered by the preorbital bone. The teeth are conical and sharp, never molar-like, and there are teeth on the roof of the mouth. The chin has no barbels or pores, and there are no spines on the opercle. Small ctenoid scales cover the body, except between the mouth and eyes. A prominent, narrowly triangular scale is present in the axil of the pelvic fin. The dorsal fin is continuous, and the caudal fin varies from deeply forked to truncate. The lateral line extends to the base of the caudal fin. Most snap pers are carnivorous. They are very important economically as commercial and sport fishes.
2 genera and about 7 species worldwide; 1 genus with 2 species in North America (1 Atlantic, 1 Pacific). Species in the genus Lobotes are marine, whereas those in the genus Datnoides occur in Indo-Pacific fresh and brackish waters. The collective common name is derived from the long rounded posterior dorsal and anal fin lobes that extend well beyond the base of the caudal fin, giving the appearance of three tails. The body is deep and compressed. The dorsal fin is very slightly notched, and has 12 stiff spines and 15 to 16 rays. There are two spines on the opercle, and the top of the head is scaled. The vomer and palatine bones are toothless. Adults float on their sides in the shade of flotsam; the young do the same, mimicking drifting leaves.
8 genera and about 40 species worldwide; 4 genera and 12 species in North America (9 Atlantic, 2 Pacific, 1 shared), plus 10 species confined to Mexican waters. Members of this family occur in tropical and warm-temperate waters; they are mostly marine, but some species enter fresh water and a few are found there permanently. These usually small fishes are never brightly colored, but may have pigment patterns of tan and brown. They are covered with silvery scales; the scales are usually embedded and adherent, but are sometimes deciduous. The top of the head, cheek, and opercle are scaled. The body is moderately to deeply compressed, and the snout is pointed. The ventral profile of the head is concave. The jaws are extremely protractile; this is made possible by long extensions of the premaxillary bone, which slip into a sheath that extends along the upper snout. When extended, the jaws point downward. A prominent axillary scale is present at the insertion of each pelvic fin. The dorsal fin, which has nine to 10 spines and nine to 17 rays, is interrupted by a shallow notch; it and the anal fin each fold into a deep sheath of scales. The anal fin has two to three (usually three) spines; the second spine is longest and often very stout. The caudal fin is deeply forked. Mojarras are bottom-dwelling fishes, usually less than 12" (30 cm) long, and are found mostly in relatively shallow water over grass, sand, or other open bottoms, but seldom around reefs. Some species, particularly those in the genus Eucinostomus, are very similar in appearance and are difficult to identify.
29 genera and about 100 species worldwide; 6 genera and 16 species in North America (15 Atlantic, 1 Pacific), plus 2 species confined to Mexican waters and 2 species sometimes entering coastal fresh waters in Florida. Porgies have oblong compressed bodies and large steep heads. The mouth is small and terminal; the maxilla is covered by a sheath when the mouth is closed, and never reaches beyond the middle of the eye. The opercle is scaled, but has no spines or serrations. The teeth are well developed, and include incisors or canines in the front of the jaws and molars in the sides. Most North American porgies have a slit-like posterior nostril. The pectoral fins are long. The continuous dorsal fin usually has l0 to 13 spines and 10 to 15 rays. The anal fin has three spines and eight to 14 rays. Some porgies live over hard bottoms, others over mud; a few species are sometimes found around coral reefs, but this is not the usual habitat. Practically all porgies occur inshore, but some are found in brackish or fresh waters.
7 genera and 33 species worldwide; 1 genus with 5 species in North America (3 Atlantic, 2 Pacific). Members of this family occur in shallow tropical to warm-temperate marine and brackish waters; four species, none in North America, are found in fresh water. The young are pelagic. Most threadfins are small to medium fishes less than 18” (46 cm) long; one Indo-Pacific species reaches a length of 6' (1.8 m). Each subabdominal pelvic fin has a single spine and five rays. Each pectoral fin is divided into two segments, the upper with attached rays and the lower with three to 15 long unattached rays. The dorsal fin is widely separated into spiny and soft-rayed segments, and the caudal fin is deeply forked. The mouth is on the underside of the head. Threadfins are important food fishes in some parts of world, but not in North America.
70 genera and about 270 species worldwide; 18 genera and 32 species in North America (23 Atlantic, 8 Pacific, 1 restricted to fresh water), plus 5 genera and 43 species confined to Mexican waters (2 Atlantic, 41 Pacific). Family members occur in tropical and temperate waters; one North American species, the only species in the genus Aplodinotus, is restricted to fresh water. These elongate and moderately compressed fishes occur in a variety of habitats, but most are bottom dwellers that live close to shore over open sand or mud. They often have chin and rostral pores, and some have chin barbels. The top of the head in some species is very cavernous. Teeth are present in the jaws, but absent on the roof of the mouth; some species have molar-like teeth on the pharyngeal bones. The dorsal fin is divided into two segments, separated by a distinct notch. The anal fin usually has two weak spines. The caudal fin is usually square or lanceolate, occasionally emarginate or shallowly forked; when lanceolate, the middle rays are often longer than the rays above and below. Drums and croakers have ctenoid scales, often covering the bases of the fins, and the lateral line always extends to the tip of the caudal fin. This is one of the most commercially important families in North America. Members of this family make a drumming sound (which gives the family its common name) by vibrating the muscles attached to the swim bladder.
6 genera and about 55 species worldwide; 4 genera and 5 species in North America (4 Atlantic, 1 Pacific), plus 1 species confined to Mexican Pacific waters. These rather elongate bottom dwellers, usually bright red or yellow, are found in tropical and warm-temperate seas. The dorsal fin is divided into two well-separated segments; the first segment has six to eight spines and the second has eight to nine rays. The anal fin has two small spines and five to eight rays. Goatfishes locate food with two large barbels that trail from the chin and fit into a groove on the throat; these movable tactile structures are used to stir up the bottom and dislodge the small organisms that occur there.
2 genera and about 25 species worldwide; 1 genus with 2 species in North America. Sweepers are found in tropical seas, but are absent from the eastern Pacific; both North American sweepers occur in the tropical western Atlantic. These usually coppery red, nocturnal fishes form large schools at mid-depths around coral reefs or rock ledges, where they feed on small planktonic organisms. Most species inhabit shallow water, but some may occur to depths of 300’ (91 m). They have a deep compressed body that usually tapers strongly to a slender caudal peduncle. The maxilla does not reach beyond the middle of the eye. The preorbital area is smooth, and the eyes are large, without adipose lids. The dorsal fin is continuous, located midway along the back, with four to seven spines and seven to 12 rays. The anal fin has two (rarely three) spines and 17 to 45 rays. The pelvic fins are thoracic in position, each with a single spine and five rays. There are usually 40 to 82 scales in the lateral line, which extends onto the caudal fin. Most sweepers are less than 6” (15 cm) long; one Indo-Pacific species reaches a length of 12” (30 cm).
10 genera and 114 species worldwide; 2 genera and 8 species in North America (6 Atlantic, 2 Pacific), plus 2 genera and 3 species confined to Mexican Pacific waters. Butterflyfishes are found in tropical coral reefs throughout the world; they are among the most characteristic and obvious fishes in this type of habitat. These small to medium fishes have deep, compressed, disk-shaped bodies. Yellow coloration dominates in many species, and most have a dark band through the eye. The snout is pointed, and the small mouth has protractile jaws. The long continuous dorsal fin has only a slight notch (sometimes no notch) between the spiny and soft-rayed segments; there are six to 16 dorsal fin spines and 15 to 30 rays. The anal fin has three to five (usually three) spines and 14 to 23 rays. The lateral line extends onto the caudal peduncle. Some butterflyfish species are solitary; others pair off early and for life.
9 genera and 74 species worldwide; 3 genera and 7 species in North America (6 Atlantic, 1 Pacific), plus 2 species confined to Mexican Pacific waters. Found in tropical seas, these brightly colored fishes have deep compressed bodies. They are so close anatomically to butterflyfishes (family Chaetodontidae) that they once were included in that group. Angelfishes differ in having a blunter snout and a large spine on the angle of the preopercle; in addition, the rays of the dorsal and anal fins are often long and filamentous. Some angelfishes are small, but others reach lengths of 24” (61 cm), larger than any species in the family. Most species inhabit shallow reefs, and are active during the day and lethargic at night. The young of some species feed on ectoparasites of other fishes, and adults sometimes feed on sponges. The color pattern of the young is sometimes different from that of adults. Two species found in the western Atlantic, Queen Angelfish (Holacanthus ciliaris) and Blue Angelfish (H. bermudensis), commonly hybridize, an extremely rare phenomenon in reef-dwelling marine fishes.
15 genera and about 42 species worldwide; 5 genera and 7 species in North America (2 Atlantic, 5 Pacific), plus 2 species confined to Mexican Pacific waters. This family is found in tropical to temperate marine waters throughout the world; it has recently been expanded to include several groups once considered distinct families, among them the nibblers (formerly family Girellidae) and the halfmoons (formerly family Scorpidae), each with a single species in North American eastern Pacific waters. Sea chubs are perch-like fishes, with oval compressed bodies and small mouths. The dorsal fin has nine to 17 spines and 11 to 28 rays. The anal fin has three spines and 10 to 21 rays. The caudal fin is lunate to almost truncate. Most species feed on algae. Some are referred to as rudderfishes because of their penchant for following ships.
9 genera and about 32 species worldwide; 1 species in North America, plus 3 genera and 3 species confined to Mexican Pacific waters. Hawkfishes are small to medium, brightly colored fishes. The lower five to seven pectoral fin rays are thickened and unbranched, with the rays projecting well beyond the fin membrane. The dorsal fin has 10 spines with cirri at the tips and 11 to 17 rays. The anal fin has three spines and five to seven rays. Hawkfishes have cycloid or ctenoid scales. Found in tropical marine shore waters, these bottom-dwelling fishes live in rock and coral habitats, where they may be observed resting on the bottom propped up by their pectoral fins.
1 genus with 6 species confined to North America. In the recent past, these fishes were considered to be part of the sunfish family (Centrarchidae). As currently recognized, the family's single genus, Elassoma, is confined to fresh water in the central and southeastern United States. Pygmy sunfishes are small fishes, all less than 2” (5 cm) long, with cycloid scales. The dorsal fin has three to five spines, and the anal fin has three spines. The caudal fin is rounded. These fishes lack a lateral line.
13 genera and about 22 species worldwide; 11 genera and 19 species in North America. Members of this family are found in cold-temperate waters along the Pacific coasts of North America and northeastern Asia, including Japan; one North American species is confined to fresh water. Surfperches have a deep compressed body with a fully exposed maxilla. The continuous dorsal fin is usually slightly notched but never deeply divided, with usually six to 11 spines (15 to 19 in one species) and nine to 28 rays. The anal fin has three spines and 15 to 35 rays. The caudal fin is notched or deeply forked. These fishes have cycloid scales, and there is usually a sheath of scales extending onto the dorsal fin. All species are viviparous; internal fertilization is facilitated by the thickened forward end of the anal fin, which aids in the transfer of sperm from the male to the female. The developing embryos receive nourishment from the female through a series of capillaries in their enlarged dorsal and anal fins.
28 genera and about 320 species world- wide; 5 genera and 19 species in North America (14 Atlantic, 5 Pacific), plus 11 species confined to Mexican Pacific waters. Damselfishes are mostly found in tropical seas, and the vast majority are associated with coral reefs; a few species occur in temperate waters. Most species are small, but a few attain lengths of more than 12” (30 cm). These fishes usually have deep, moderately compressed bodies and are brightly colored, especially when young. The mouth is small, but the jaws are very protractile. There is usually a single nostril on each side of the snout (a small obscure second nostril is present in two genera), a characteristic that distinguishes this family from all similar ones except the mostly freshwater cichlids (family Cichlidae). The slightly notched dorsal fin has eight to 17 (usually 10 to 14) spines and 11 to 18 rays, and the base of the spiny segment is always longer than the soft-rayed segment. The anal fin almost always has two spines (rarely three) and nine to 16 rays. The scales are ctenoid, and the incomplete lateral line usually ends under the soft dorsal fin. Males assume parental care of the eggs. Included in this family are the brightly colored and distinctively patterned Indo-Pacific anemonefishes (genus Amphiprion), which have the unusual habit of living among the tentacles of poisonous sea anemones. Because of their interesting habits and attractive colors, members of this family are a common component of home and public marine aquariums. The taxonomy of certain genera is difficult, mainly because of pronounced color changes between the young and adults. All Atlantic and eastern Pacific species formerly classified as members of the genera Pomacentrus and Eupomacentrus are now included in the genus Stegastes.
At least 60 genera and roughly 500 species worldwide; 13 genera and 25 species in North America (21 Atlantic, 4 Pacific), plus 2 genera and 15 species confined to Mexican Pacific waters. The second-largest marine fish family, Labridae is one of the most diverse in terms of shape, color, size, and temperature requirements. Most wrasses live in tropical or subtropical seas, but some occur in warm-temperate or even cold-temperate waters. The body shape ranges from pencil-like to deep and extremely compressed. Many species are highly colorful, making them popular aquarium fishes, and several color patterns (often sexually oriented) may exist within a single species. The mouth is terminal and protractile, with conspicuously thick lips. There are often strong canine teeth in the jaws and conical teeth on the pharyngeal bones, but none on the roof of the mouth; the jaw teeth are mostly separate and usually project outward. The dorsal fin has eight to 21 (usually fewer than 15) weak spines, lying low to the back, and six to 21 rays; the spiny and soft segments are not obviously separate. The anal fin has two to six (usually three) spines and seven to 18 rays. These fishes have medium to large cycloid scales; there are 25 to 80 scales in the lateral line, which follows the contour of the back. Some species reach a length of only 2" (5 cm), whereas at least one Indo-Pacific species reaches a length of more than 7’ (2.1 m). Most small species are cleaners, picking ectoparasites off larger fishes. Wrasses propel themselves by sculling movements of the pectoral fins, and the majority bury themselves in sand at night. They are closely related to parrotfishes (family Scaridae), and display many of the same physical and behavioral characteristics.
9 genera and 83 species worldwide; 4 genera and 15 species in North America (14 Atlantic, 1 Pacific), plus 1 genus and 5 species confined to Mexican Pacific waters. These colorful, diurnal, herbivorous fishes abound on reefs of shallow tropical seas. The teeth are fused to form a pair of beak-like dental plates in each jaw (the basis for the family's common name), which are joined at the front of the jaws and in most genera are separated by a median groove; the groove is absent and the individual teeth fused together but distinguishable in a few of the more primitive genera. The paired upper and lower pharyngeal bones contain rows of molar-like teeth (the pharyngeal mill), which are used to grind up algae associated with the coral rock or sediment that is often ingested (parrotfishes thus are the primary producers of the coralline sand found around reefs). Most species have an oblong, moderately compressed body, with the head usually bluntly rounded anteriorly. All species have a continu ous dorsal fin with nine flexible spines and 10 rays, and an anal fin with three spines and nine rays. All fins are unscaled. The scales on the body are large and cycloid. The lateral line usually has 22 to 24 scales and follows the contour of the back to below the rear portion of the dorsal fin. Sexual dimorphism is pronounced in many species, which has led to past taxonomic confusion. The drab- colored young are male or female (the primary phase), with many maintaining this coloration into sexual maturity; some females apparently later change into brightly colored (with combinations of red, green, and blue) terminal males, which have been found to exhibit different reproductive behavior than primary-phase mature males. Parrotfishes are related to the wrasses (family Labridae) and exhibit many of the same physical and behavioral features. Slender-bodied parrotfish genera, such as Cryptotomus, so closely resemble wrasses in outward appearance that even specialists can be fooled. Both families are strongly diurnal and undergo a form of sleep at night, at which time some species may secrete a protective transparent mucal cocoon.
3 genera and at least 7 species worldwide; 3 genera and at least 6 species in North America. This family is confined to cold-temperate inshore marine waters on both sides of the North Pacific. They are slender elongate fishes with large eyes; they reach lengths of up to 12" (30 cm). Both the dorsal and anal fins are long, continuous, and uniformly parallel with the body, and neither is joined to the caudal fin. The dorsal and anal fins are composed almost entirely of rays (some species have a few weak spines at the front of the fins); there are 41 to 48 dorsal fin rays and 30 to 36 anal fin rays. The thoracic pelvic fins are just in front of the pectoral fins, and each has a single weak spine and five rays. The pectoral and caudal fins are rounded. The body is covered with numerous small, deeply embedded ctenoid scales. Ronquils have a straight lateral line, located high on the body and extending only to near the end of the dorsal fin.
About 46 genera and about 220 species worldwide; 10 genera and 34 species in North America (7 Atlantic, 20 Pacific, 7 shared), with additional species in deeper waters farther offshore. Eelpouts are mostly confined to cold-temperate to arctic waters of the North Pacific, North Atlantic, and Arctic Oceans; a few species inhabit seas of comparable temperatures around the southern continents, including Antarctica, but the family is absent from intervening tropical regions. North American eelpouts are found in shallow to moderately deep waters, usually to depths of 656' (200 m). Most are bottom dwellers; a few are free-swimming mid-water fishes, as are the early-life stages of some bottom species. These fishes have an elongate tapering body with a relatively large head. The mouth is often big, with thick lips, and the upper jaw usually projects beyond the lower jaw. The long dorsal and anal fins are usually joined to the pointed caudal fin, extending unbroken around the end of the body. The pelvic fins, when present, are tiny and thoracic, just in front of the pectoral fins. Most species have fins without spines. When present, the scales are tiny and cycloid, embedded in the skin and difficult to see. Most species are oviparous, but a few are ovoviviparous. The concepts of the evolutionary relationships of this family to other fish families have changed greatly through time; prior to their current position in the order Perciformes, the eelpouts were thought to be closer to the codfishes (family Gadidae), cusk-eels (family Ophidiidae), and their relatives in the order Gadiformes.
About 36 genera and about 65 species worldwide; 22 genera and 33 species in North America (3 Atlantic, 25 Pacific, 5 shared). This family is confined to cold-temperate waters of the North Pacific and Atlantic Oceans, with the greatest abundance in the Pacific. Most of these eel-like, elongate, compressed bottom fishes live in the tidal zone among rocks and vegetation. When present, the pelvic fins are small and thoracic, each with one spine and two to four rays. The dorsal and anal fins are long, extending almost to the tail, but they are joined to the caudal fin in only a few species. The dorsal fin origin is just behind the head. The anal fin, which consists of one to five small spines, begins at or before the mid-body. Some pricklebacks are unscaled; when present, the scales are tiny, cycloid, and deeply embedded. The lateral line is either faint, incomplete, or absent; when present, it occasionally has four main branches with vertical side branches. The gill membranes are sometimes medially joined. Pricklebacks have brown, red, or yellow coloring, and, in some species, faint bars or stripes. They are similar to the gunnels (family Pholidae), and are best distinguished by their longer anal fin.
4 genera and about 13 species worldwide; 4 genera and 10 species in North America (1 Atlantic, 8 Pacific, 1 shared). Gunnels are confined to cold-temperate marine waters of the North Pacific and Atlantic Oceans, with the greatest abundance in the Pacific. They are eel-like fishes with long, slender, compressed bodies; most species are less than 12” (30 cm) long. The teeth are small and conical. The pelvic fins are rudimentary or absent; when present, they have a single spine and a single ray. When present, the pectoral fins are very small, with seven to 17 rays. The dorsal fin is twice as long as the anal fin; both fins are usually joined to the caudal fin. The dorsal fin consists of 75 to 100 flexible spines; the anal fin has one to two spines and usually 30 to 45 rays. The cycloid scales are usually inconspicuous and covered with thick mucus. The lateral line is short or absent altogether. Most gunnels live in the intertidal zone in shallow water, hiding among rocks and crevices near algae. They are very similar to the pricklebacks (family Stichaeidae), and are best distinguished by their shorter anal fin.
2 genera and 5 species worldwide; all found in North America (2 Atlantic, 2 Pacific, 1 shared). This family is confined to cold-temperate marine waters of the North Pacific and Atlantic Oceans. The largest of these eel-like fishes exceeds a length of 8' (2.4 m). Pelvic fins are absent, and the pectoral fins are large. The dorsal fin is composed of numerous flexible spines. The anal fin has numerous rays and sometimes a single spine. The small caudal fin is usually pointed. The gill membranes are attached to the isthmus. Wolffishes are usually unscaled and lack a lateral line; when present, the scales are small and cycloid. They have strong jaws with large, peg-like canine teeth in the front and molar-like teeth in the rear, with which they can cause serious wounds.
5 genera and about 18 species worldwide; 1 genus with 3 species in North America, plus 1 species confined to Mexican Pacific waters. This family is found in cool to tropical waters in the Arctic, Atlantic, Indian, and Pacific Oceans; species in tropical regions occur in deeper colder waters. These small, eel-like fishes are quite long, and swim with an undulating motion. Unlike eels, they have wide gill openings, a large opercle, a forked caudal fin, and small cycloid scales. Sand lances have long dorsal and anal fins, both without spines; the dorsal fin has 40 to 69 rays, and the anal fin has 14 to 36 rays. Pelvic fins are usually absent (present in one genus). The lateral line is high, close to the dorsal fin. Sand lances lack teeth, and the premaxillae are protractile in all but one genus.
8 genera and about 50 species worldwide; 3 genera and 6 species in North America (4 Atlantic, 2 Pacific). This family is found in shallow to moderately deep tropical to temperate seas throughout the world, usually along continental shores with open bottoms. Stargazers are heavy-bodied fishes with flat to broadly rounded heads. The mouth is large and extremely oblique, with fringed lips. Some species have a small, worm-like filament extending from the floor of the mouth, which functions as a “lure.” Two large, double- grooved spines, each with a venom gland at the base, may be present just above the pectoral fin and behind the opercle. The small eyes project dorsally upward. The body is unscaled or covered with small scales. The pelvic fins each have a single spine and five rays, narrowly separated from one another, and are located under the throat well ahead of the large rounded pectoral fins. The dorsal fin in some species is composed entirely of rays; in others, there are usually four short, relatively low spines completely separated from the soft dorsal fin. In all stargazers, the soft dorsal fin is moderately long, usually containing 10 to 13 rays. The anal fin has 12 to 18 rays. Members of this family burrow, covering themselves with a layer of sand or silt, the eyes protruding just above the head; the fish ambushes its prey as it passes by or comes to investigate the worm-like “lure” in the floor of the mouth. Portions of the eye muscle in members of the genus Astroscopus are modified into weak electric organs; whether the electric organ is used as an aid in capturing prey is uncertain.
20 genera and at least 115 species worldwide; 1 genus with 3 species in North America, plus 2 genera and 8 species confined to Mexican Pacific and Atlantic waters. This family occurs in shallow tropical to temperate seas, usually around coral reefs or rocks. The pelvic fins are located under the throat, in front of the well-developed pectoral fins. The dorsal fin is divided into three distinct and often completely separated segments. The first dorsal fin segment is shorter than the second, and both are composed entirely of spines: three to six in the first segment, and 11 to 23 (usually 16 or more) in the second. The third dorsal fin segment consists of seven to 14 rays. The anal fin is either spineless or has one to two (usually two) spines and 15 to 28 rays. There are no cirri on the nape. The gill membranes of triplefins are broadly attached across the isthmus. The premaxillae are protractile. The scales are usually ctenoid. The maximum length of these fishes is about 10” (25 cm), but most species reach lengths of less than 2 1/4" (6 cm). This family was once included in the wide-ranging family Clinidae (now known as the kelp blennies).
9 genera and 41 species worldwide; 3 genera and 8 species in North America, plus 12 species confined to Mexican Pacific waters. This family is restricted to sandy shores and sandy areas around coral reefs or along coasts in tropical to warm-temperate seas from North to South America; it is one of only a few marine families confined to the Western Hemisphere. Sand stargazers are small fishes with moderately elon gate, tapering bodies that are compressed posteriorly. The pelvic fins, each with a single spine and three rays, are located under the throat, in front of the well-developed pectoral fins. The dorsal fin is long and continuous, sometimes with one or two notches, and has seven to 23 spines and 12 to 36 rays. The long anal fin begins under the middle of the pectoral fin and has two spines and 21 to 41 rays. The dorsal and anal fins are not joined to the rounded caudal fin. The scales are cycloid, with 33 to 73 in the lateral line; the lateral line is high anteriorly, then arches abruptly downward near the pectoral fin and continues posteriorly on the mid-side of the body. These fishes have extremely oblique mouths; many species have fringed lips, which permit a free flow of water over the gills and keep out sand particles. The eyes are high on the body, somewhat protruding, and often on a stalk. The upper edge of the gill cover is subdivided into finger- like protrusions, and the gill membranes are separate and free from the isthmus. Sand stargazers are never brightly colored, but the overall pigmentation varies from nearly pallid to strongly marked by broad crossbands. These fishes bury themselves in the sand, leaving only their eyes barely exposed, lying in wait for passing prey.
14 genera and about 91 species worldwide; 7 genera and 22 species in North America (19 Atlantic, 3 Pacific), plus 3 genera and 33 species confined to Mexican Atlantic and Pacific waters. The Labrisomidae is one of the very few marine families al most entirely confined to the Western Hemisphere; the exceptions are two species from western Africa (one of which is also found in the western Atlantic). These moderately elongate, usually tapering fishes typically inhabit tropical to warm-temperate seas from shallow waters to mid-depths around coral reefs or rocky coasts. Labrisomid blennies are covered with large cycloid scales that are never embedded; as a group they are sometimes known as scaly blennies. Fleshy cirri may be present on the nape and near the eyes or nostrils. The dorsal fin is continuous; the relative number of dorsal fin spines and rays is variable (some species have only spines), but there are always more spines than rays. The long anal fin has numerous rays, and the caudal fin is rounded. The pectoral fins are large and located along the mid-sides; the thoracic pelvic fins have two to three visible rays and are located just in front of the pectoral fins. Most species have external fertilization, but males of the genus Starksia have the anteriormost anal fin ray modified into a long organ that serves as a conduit for transmitting sperm. A few eastern Pacific species are viviparous. Previously included in the wide-ranging family Clinidae (now known as the kelp blennies), this group was only recently elevated to family status. Phylogenetic relationships of the labrisomid blennies are still under study, and two genera (Stathmonotus and Neoclinus) once included in this family were recently placed in the closely related tube blenny family (Chaenopsidae).
About 20 genera and 73 species worldwide; 2 genera and 4 species in North America (all Pacific). This family occurs mostly in cool-temperate waters in rocky habitats of both the Northern and Southern Hemispheres, but is absent from intervening tropical waters; no kelp blennies are found in the western North Atlantic, and only one Mediterranean species occurs in the eastern North Atlantic. These fishes have moderately to markedly elongate bodies that are compressed posteriorly. The long dorsal and anal fins are sometimes joined to the caudal fin. The continuous dorsal fin is sometimes slightly notched, containing a combination of spines and rays, but always with more spines than rays; the anal fin has two spines and numerous rays. The cycloid scales are usually small and embedded. Kelp blennies do not have cirri on the nape. The maximum length of these fishes is 24” (61 cm); most species are much smaller. Ongoing studies have brought about radical changes in the classification of the Clinidae in recent years; several groups once included in the family have been recognized as distinct families, including the labrisomid blennies (Labrisomidae), the tube blennies (Chaenopsidae), and the triplefins (Tripterygiidae).
11 genera and at least 67 species worldwide; 7 genera and 17 species in North America (13 Atlantic, 4 Pacific), plus 2 genera and 22 species confined to Mexican Atlantic and Pacific waters. This family is almost entirely confined to coral reef or rocky habitats in tropical waters of North and South America. Tube blennies have a slender elongate body that is not usually notably tapering toward the tail. The body is usually unscaled and lacks a lateral line. Cirri are sometimes present above the eyes, on the rim of the nostrils, and on the sides of the nape. The head is often spiny or rough, with various types of bony protuberances in some species. The pectoral fins have 12 to 15 rays; the pelvic fins are located on the throat, slightly ahead of the pectoral fins. The continuous dorsal fin has 17 to 28 spines and 10 to 38 rays; in some species the anterior portion is much higher than the rest of the fin. The anal fin has two spines and 19 to 38 rays. The rounded caudal fin is either separate or variously united with the dorsal and anal fins. Classification of the family has changed considerably; until recently the group was included in the family Clinidae (now known as the kelp blennies), along with the related families Labrisomidae (labrisomid blennies) and Tripterygiidae (triplefins). More recently, two genera (Stathmonotus and Neoclinus) formerly included in the family Labrisomidae were transferred to the Chaenopsidae; this action resulted in the expansion of the range limits of the Chaenopsidae to include a limited area of the western North Pacific Ocean (Taiwan to Japan). Members of this family are sometimes collectively referred to as pikeblennies or flagblennies.
53 genera and about 345 species worldwide; 9 genera and 22 species in North America, plus 3 species confined to Mexican Pacific waters. These bottom-dwelling fishes occur mostly in shallow waters of temperate to tropical seas, very rarely in fresh water but occasionally in brackish water. They are small, unscaled, and usually drably colored. Robust and deep-bodied, they have a blunt snout and a steep head profile. Each jaw has a single row of comb-like incisor teeth, and some species also have canine teeth; the incisor teeth are either firmly set in the jaws or are freely movable. Feather-like cirri are present above the eyes and sometimes on the nape. The pelvic fins, each with only two to four visible rays, are inserted in front of the pectoral fins. The dorsal fin is long and continuous or slightly notched, with three to 17 flexible spines and nine to 19 rays (most species have fewer spines than rays); the base of the spiny segment is shorter than the soft-rayed segment. Combtooth blennies usually have two flexible anal fin spines.
About 36 genera and about 120 spe cies worldwide; 4 genera and 10 species in North America (3 Atlantic, 7 Pacific), plus 3 genera and 24 species confined to Mexican waters (including 3 freshwater species). Clingfishes are found mostly in tropical to warm- and cold-temperate seas throughout the world; four Mexican and Central American species are restricted to fresh water. The family has a peculiar distribution: The greatest diversity of genera and species worldwide is in cold-temperate waters, particular those of the Southern Hemisphere, yet in North America the greatest diversity is in the tropics, particularly in the Gulf of California. These small, unscaled, tadpole-shaped fishes have a complex sucker-like disk on the ventral surface composed of modified pelvic fins and parts of the pectoral fins. They use the disk mostly to attach themselves to rocky bottoms in the surf zone, but sometimes they cling to plants. The disk has patches of short papillae; the arrangement of these patches is useful for identification. The dorsal and anal fins are soft-rayed. Most clingfishes are less than 2" (5 cm) long, but two species reach lengths of about 12" (30 cm). Phylogenetic relationships of this family have long puzzled ichthyologists, and its placement within fish classifications has changed many times throughout the years.
18 genera and about 130 species worldwide; 4 genera and 5 species in North America (4 Atlantic, 1 Pacific). Dragonets occur in tropical to warm-temperate seas; the great majority of species are found in the tropical Indo-Pacific region, from near shore to depths of 2,100’ (641 m) or more. These benthic fishes live over soft to hard bottoms, and many are found around coral reefs. They have a tapering body with a slender caudal peduncle, and are usually brightly colored and strikingly pigmented, particularly those species inhabiting coral reefs. They reach lengths of about 10” (25 cm). The pectoral and pelvic fins are well developed, the latter thoracic and in front of the pectoral fins; the inner ray of each pelvic fin is connected to the body by a membrane. The dorsal fin is divided into two distinct segments. The first dorsal fin has four flexible spines and is usually short-based, highly elevated, and brightly colored (especially in males); the second dorsal fin has six to 11 rays. The anal fin is composed of four to 10 rays. The caudal fin is rather elongate, with the middle rays sometimes greatly extended in males. The head is triangular when viewed from above. The eyes are large and bulbous, situated near the top of the head and directed upward. The small terminal mouth has strongly protractile jaws. The small gill opening is on the upper side of the head. The preopercle is usually armed with a strong spine at the tip that sometimes has up to three forward-projecting, supplementary hooks on the inner edge; the opercle and subopercle lack spines. Dragonets have a complete lateral line that extends to the caudal fin base. Sexual dimorphism is usually apparent in these fishes, especially in regard to the size and development of the dorsal fin.
About 212 genera and roughly 1,875 species worldwide; about 35 genera and 71 species in North America (59 Atlantic, 12 Pacific), plus 6 species introduced and established in Canada and United States and 7 genera and 51 species confined to Mexican waters. The vast majority of gobies are found around tropical reefs, but many live in warm- or cold-temperate marine waters, and some (including 11 North American species) permanently or occasionally occur in fresh water. The Gobiidae is one of the two largest families of fishes in the world, equaled or exceeded only by the freshwater family Cyprinidae (carps and minnows). These small fishes have elongate robust bodies and are variably colored and marked. The family includes some of the smallest fishes known; a number of gobies are less than 1/2" (1.5 cm) long when fully grown. In most species, the inner rays of the pelvic fins are united by a membrane, forming a sucking disk with which the fish clings to the bottom. There may be another membrane (the frenum) across the front of the disk between the pelvic fin spines. In some species, the pelvic fins are separate. The broad-based pectoral fins are inserted just above the pelvic fins. The dorsal fin is either deeply notched or divided into two separate segments; North American gobies usually have six to seven dorsal fin spines. The distance between the end of the second dorsal fin and the caudal fin base is less than the length of the second dorsal fin base. The dorsal and anal fins are not joined to the caudal fin. The species now assigned to the sleeper family (Eleotridae) were once included with the Gobiidae, primarily because of confusion over the significance of the separated pelvic fins found in certain goby species.
About 35 genera and at least 150 species worldwide; 5 genera and 8 species in North America (6 Atlantic, 2 Pacific), plus 3 species confined to Mexican waters. This family is found in tropical to temperate marine, brackish, and fresh waters; only one North American species appears to be entirely restricted to a marine habitat. These elongate robust fishes are drably colored and often have irregular mottling. The pelvic fins are inserted close to each other near the insertion of the pectoral fins but, unlike those of most gobies, are not united to form a disk. The distance from the end of the second dorsal fin to the base of the caudal fin rays is equal to or longer than the length of the second dorsal fin base. This group was once included in the family Gobiidae, primarily because of confusion over the significance of the separated pelvic fins found in certain gobies.
7 genera and about 20 species world- wide; 1 genus with 2 species in North America (1 Atlantic, 1 Pacific), plus 1 species confined to Mexican Pacific waters. Most members of this family are found in tropical marine or brackish waters. Spadefishes are similar to butterflyfishes (family Chaetodontidae) in that their bodies are very deep, disk-shaped, and compressed; this body shape allows them to make quick and easy lateral movements in confined places such as shipwrecks. The small mouth is not protractile, a feature that distinguishes spadefishes from butterflyfishes. The stout dorsal fin spines are separate from or slightly connected to the dorsal fin rays.
6 genera and about 72 species worldwide; 1 genus with 3 species in North America (all Atlantic), plus 1 genus and 5 species confined to Mexican Pacific waters. Surgeonfishes occur in tropical coral reefs. The body is deep and compressed, and the eyes are located high on the head. The small mouth has spatula-shaped, finely serrate teeth. These fishes have a continuous dorsal fin with nine spines. The caudal fin is emarginate. The collective common name is derived from the hinged scalpel-like spine that folds into a groove on either side of the caudal peduncle; these spines (each actually a modified scale) are present in most species. When the fish is moving, it can lash out the spines at other fishes, either to warn or injure. Surgeonfishes are not known to attack divers, but they should be handled carefully. All species are strictly herbivorous. Members of this family are also known as doctorfishes or tangs.
1 genus with 20 species worldwide; 6 species in North America (4 Atlantic, 2 Pacific), plus 1 species confined to Mexican Pacific waters. Barracudas are found in a variety of habitats, ranging from coral reefs to estuaries, in tropical and subtropical waters throughout the world. These elongate fishes have dark bars, chevrons, stripes, or dark blotches. The pelvic and pectoral fins are small; the pelvic fins are inserted more or less under the dorsal fin origin, and the pectoral fins are inserted in front of the pelvic fin bases. There are two widely separated dorsal fins; the first consists of five spines, the second has a spine in front of the rays. The second dorsal and anal fins are mirror images. Barracudas are voracious predators that feed mainly on other fishes. They may be solitary or gregarious, largely depending on the species and the size of the individual. Although they are good food fish, care should be taken in eating large individuals, as they have often been implicated in ciguatera poisoning. Barracudas have formidable teeth that are capable of inflicting serious wounds; in North America, only Great Barracuda (Sphyraena barracuda) reaches a sufficiently large size to be of any potential danger. In general, their danger to people has been greatly exaggerated, and the attacks that have occurred have been by accident. Once allied with the mullets (family Mugilidae), largely because of the similar positions of the widely separated dorsal fins, this family is now believed to have a closer relationship to the mackerels and tunas (family Scombridae).
16 genera and about 23 species worldwide; 4 genera and 7 species in North America (3 Atlantic, 4 Pacific). These silvery elongate fishes are found in tropical and subtropical seas, often in very deep water. Their long jaws are armed with large canine or lance-like teeth. When present, the pelvic fins are small. The long dorsal fin usually continues from behind the head to the tip of the tail.
15 genera and 49 species worldwide; 9 genera and 24 species in North America (9 Atlantic, 8 Pacific, 7 shared). Members of this family, which includes mackerels and tunas, are found in tropical to cold-temperate seas throughout the world. These torpedo- shaped fishes are prized commercially and for sport. The pelvic fins are either beneath or slightly in front of the pectoral fins, and the pectoral fins are inserted above the mid-axis of the body. The dorsal fin is divided into two sometimes well-separated segments; when depressed, each segment fits into a groove. The first dorsal fin begins well behind the head, and has nine to 27 spines. There are five to 12 finlets between the second dorsal fin and the caudal fin, and between the anal fin and the caudal fin. Mackerels and tunas have two or three pairs of keels on the caudal peduncle. The scales are small and cycloid; some species have a corselet of large thick modified scales behind the head that encircles the back and extends along the lateral line. Some species are endothermic, with elevated body temperatures. Because mackerels and tunas are fast-swimming, schooling fishes occurring in open seas, some have cosmopolitan distributions.
1 species worldwide. This family occurs in tropical and temperate open seas throughout the world. These large distinctive fishes have a long snout; the anterior upper jaw and nasal bones are modified to form a sword, and the jaws lack teeth. The gill membranes are free from the isthmus. Adult swordfishes lack pelvic fins. The two dorsal fins are widely separated, the first much larger than the second. The caudal peduncle has a single keel. Adults are unscaled. Although swordfishes superficially resemble the closely related billfishes (family Istiophoridae), a group that has sometimes been considered a subfamily of the Xiphiidae, the two families may be readily distinguished by the presence or absence of teeth, pelvic fins, keels on the caudal peduncle, and body scales.
3 genera and about 11 species worldwide; 3 genera and 7 species in North America (2 Atlantic, 3 Pacific, 2 shared). Members of this family are found in tropical and temperate open seas throughout the world. They are closely related to swordfishes (family Xiphiidae), and until recently were included in that family. Billfishes and swordfishes have an elongate snout that forms a sword or spear and a deeply forked, lunate caudal fin. Billfishes differ from swordfishes in having the snout rounded rather than flat in cross section, teeth in the jaws, pelvic fins, scales, and, in adults, two keels on the caudal peduncle. The pectoral fins are on the lower mid-sides of the body, usually pointed backward but not downward. The dorsal fin is divided into two narrowly separated segments. The first dorsal fin is long-based, depressible into a groove, and is very high and fan-like in all individuals less than 3’ (91 cm) long; with the exception of the genus Istiophorus, all but the anteriormost rays become notably shorter in larger individuals. The anal fin is divided into two widely separated segments. There is usually one lateral line, but it may be branched to form a chain-like pattern.
3 genera and about 15 species worldwide; 3 genera and 7 species in North America (5 Atlantic, 1 Pacific, 1 shared), plus 1 species confined to Mexican Pacific waters. These fishes live near the surface of tropical and subtropical open seas, often in association with floating seaweed or other objects. The pelvic fins may be either large or small. There are two joined dorsal fins, the first with nine to 12 spines, the second with up to three spines and 15 to 32 rays. The anal fin has one to three spines and 14 to 31 rays. The caudal fin is forked. The lateral line runs high on the side, along the dorsal fin base. Driftfishes also have a system of mucous canals along the side that is usually visible through the skin.
3 genera and about 13 species worldwide; 1 genus with 5 species in North America (3 Atlantic, 2 Pacific), plus 2 species confined to Mexican Pacific waters. This family is found in tropical to temperate coastal waters throughout the world. These fishes are short, deep, and compressed; the upper profile is a mirror image of the lower. Butterfishes are gray to blue or green above and have intense silvery reflections, especially on the lower sides and the belly. The mouth is small, not protractile, and located at the end of a blunt snout. Pelvic fins are absent in adults. The pectoral fins are long and pointed. The dorsal and anal fins are long-based, and each has only two to six weak spines. The caudal peduncle is narrow and lacks keels. The scales are cycloid, and the lateral line is parallel to the dorsal profile. Until recently this family included species now placed in five other families, the Nomeidae (driftfishes), Centrolophidae (medusafishes), Ariommatidae (ariommatids), Tetragonuridae (squaretails), and Amarsipidae (which consists of a single Indo-Pacific species).
Order Pleuronectiformes
This order consists of 11 families, six of which are found in North America; it contains the flounders, halibuts, soles, and tonguefishes, which are collectively known as flatfishes due to their highly compressed bodies. When first hatched, flatfishes have one eye on each side of the head, like any other vertebrate, but as they develop one eye moves to the opposite side. In some families, the eyes are on the left side; other families have the eyes on the right side. (Rarely, however, an individual that would normally be left-eyed has eyes on the right side, or vice versa.) The eyed side is usually pigmented, and the blind side has very little pigment or is plain white. Some species have distinct spots or rings on the eyed side. The pelvic fins are usually asymmetrical in both size and position (the relative size and position of these fins are of considerable taxonomic importance). The pectoral fin on the blind side is often reduced or absent; occasionally both pectoral fins are absent. The dorsal and anal fins are long, continuous, and soft-rayed. Many species are capable of remarkable instantaneous color changes to match their environment. Flatfishes live on the ocean bottom, resting with the blind side downward; they swim on their side with the eyes facing upward. They usually lie partially buried on the seafloor and dart quickly upward to seize passing prey. All flatfishes are edible.
20 genera and at least 115 species worldwide; 5 genera and 9 species in North America (8 Atlantic, 1 Pacific), plus 2 species confined to Mexican Pacific waters. These highly compressed flatfishes are found over open bottoms in tropical to temperate seas throughout the world. The eyes and pigmentation are usually on the left side of the body. The pigmented side is usually brownish, often with markings, and the blind side is white; these fishes are capable of changing color patterns to match the substrate. The edge of the preopercle is visible and not hidden by skin. The pelvic fin base on the eyed side is longer than on the blind side. The dorsal fin base is long, beginning above or in front of the eyes and, like the anal fin, is not connected to the caudal fin. Some species exhibit sexual dimorphism, most notably in a greater distance between the eyes and longer pectoral fins in males. Many species formerly included in this family are now placed in the families Scophthalmidae (turbots) and Paralichthyidae (sand flounders); the most obvious external differences by which these families may be distinguished pertain to the placement and relative lengths of the pelvic fin bases.
5 genera and about 18 species world- wide; 1 species in North America. Turbots are confined to temperate waters of the Atlantic and the Mediterranean Sea. The eyes are usually on the left side of the body. The mouth is large, with a prominent lower jaw. These flatfishes were recently separated from the lefteye flounders (family Bothidae) as a distinct family; external morphological characteristics are virtually identical in the two groups, the principal difference being that both pelvic fin bases are elongate in turbots.
About 16 genera and at least 85 species worldwide; 9 genera and 32 species in North America (24 Atlantic, 8 Pacific), plus 13 species confined to Mexican Atlantic and Pacific waters. Sand flounders are found mostly in tropical to warm-temperate waters of the Atlantic, Pacific, and Indian Oceans; some species occasionally enter fresh water. The eyes are usually on the left side of the body. The size of the mouth varies from large to small, with teeth ranging from large and strong to small and weak. These fishes were recently separated from the lefteye flounders (family Bothidae) as a distinct family; external morphological characteristics are virtually identical in both groups, the principal differences being that sand flounders have pectoral fins with branched rays and pelvic fins with short bases of nearly equal length (the base on the eyed side is attached to the ventral ridge).
26 genera and about 59 species worldwide; 16 genera and 33 species in North America (6 Atlantic, 26 Pacific, 1 shared), plus 1 species confined to Mexican Pacific waters. This family is found in cold-temperate to arctic waters of the North Atlantic and Pacific; one eastern Pacific species commonly enters fresh water. Most righteye flounders are found over soft bottoms. They almost always have the eyes on the right side. These flatfishes have a deep, very compressed body. The pelvic fins are symmetrically placed. The dorsal fin origin is usually near the eyes, and the anal fin origin is below the pectoral fin; both are elongate, extending almost to the caudal fin base, and are composed of only rays. The caudal fin is truncate, rounded, pointed, or slightly notched. The scales are either ctenoid or cycloid; in some species, they are ctenoid on the eyed side and cycloid on the blind side. The lateral line is straight or highly arched over the pectoral fin, and some species have a dorsal branch off the lateral line. As a result of recent studies, the 20 species from cold-temperate oceans of the Southern Hemisphere formerly included in the Pleuronectidae have been placed in different families.
9 genera and about 28 species worldwide; 3 genera and 6 species in North America (5 Atlantic, 1 Pacific) plus 7 species confined to Mexican waters. This family is found mostly in shallow coastal waters to depths of about 600' (183 m) on the Atlantic and Pacific coast of the American continents; one Atlantic species regularly occurs in fresh water during the juvenile stage. Formerly included in the sole family (Soleidae), this group has only recently been accorded family status; it is one of the few marine families restricted to the American continents. These flatfishes have a rounded or oval body, with tiny, closely set eyes on the right side. They are usually blackish brown, with blotches or bars. The head is rounded, and the snout is basically absent. The tiny mouth is oblique, and the lips are fleshy and usually fringed with dermal flaps. The edge of the preopercle is hidden by skin. All fins are soft-rayed. Pectoral fins are sometimes absent. The long dorsal and anal fins are not joined to the caudal fin. Tiny ctenoid scales are usually present, but are completely absent in the genus Gymnachirus. The lateral line is almost straight and often crossed with accessory branches or minute fleshy flaps.
3 genera and more than 110 species worldwide; 1 genus with 14 species in North America (13 Atlantic, 1 Pacific), plus 7 species confined to Mexican Pacific waters. Tonguefishes are found in tropical and subtropical seas throughout the world. They are tongueshaped flatfishes that posteriorly taper to a narrow point. The tiny, closely set eyes are on the left side of the body, which is brownish with darker bars or blotches. The mouth is quite small, and the edge of the preopercle is hidden by skin and scales. The scales are ctenoid. All fins are softrayed. Pectoral fins are absent. The long dorsal and anal fins are joined to the caudal fin. There are 10 to 14 caudal fin rays; the number of caudal fin rays can be an important diagnostic characteristic, which is very unusual among fishes. In the western Atlantic, and perhaps elsewhere, species have markedly distinct depth distributions, which also can be anaid in identification. These flatfishes exhibit an obvious relations hip to the soles (family Soleidae) and American soles (family Achiridae), and have sometimes been placed in the family Soleidae.
11 genera and about 40 species worldwide; 4 genera and 8 species in North America (5 Atlantic, 2 Pacific, 1 shared), plus 2 species confined to Mexican Pacific waters. This family is found in tropical to temperate seas throughout the world. Some family members are brightly colored fishes that live along rocky coasts or around coral reefs and surrounding sea-grass beds, usually in shallow water; others live in open seas. The young are pelagic; those of some species are part of the floating sargassum community. Triggerfishes have an oval compressed body covered with large, thick, diamond-shaped scales in a regular series, resembling a coat of mail. The scales just above the pectoral fin base are usually enlarged and slighty separated to form a flexible tympanum that probably serves to transmit sound to the fish. When present, the pelvic fins are reduced to spiny projections of the pelvic bone. There are two well-separated dorsal fins. The first dorsal fin has three spines, the first spine can be locked into an upright position by the second, and the third is often minute. (only after the second dorsal fin spine has been depressed can be the first to be lowered; hence the collective common name triggerfish.) The upper jaw has an outer series of four strong teeth on each side; the premaxilla has an inner series of three teeth on each side, developed more for crushing than for nibbling. Some triggerfishes are good fishes, but others are toxic.
About 31 genera and about 95 species worldwide; 4 genera and 10 species in North America (9 Atlantic, 1 Atlantic and Pacific), plus 1 species confined to Mexican Pacific water. This family is found in tropical to warm-temperate waters of the Atlantic, Indian, and Pacific Oceans; the greatest abundance of species is found in Australia. Filefishes are small to medium, highly compressed fishes. They have two well-separated dorsal fins. In most species, the first dorsal fin has two spines (a few species have only one) the second spine is tiny and always less than one third the length of the first. The first dorsal fin spine usually can be locked upright by the second. The body is covered with tiny, modified, bristle-like scales that are not discernible to the naked eye. Filefishes have a well-developed pelvic bone that is hinged to the girdle and supports a ventral flap of skin between its tip and the anus; the pelvic bone can be moved to expand or contract the ventral flaps. In some species the flap is highly pigmented and probably used in courtship displays. When present, the pelvic fins are rudimentary, represented by a series of up to three scales covering the end of the pelvic bone. The young of certain species are components of pelagic sargassum communities. Filefishes are closely related to triggerfishes; in the past, the two groups have been lumped together in the family Balistidae and collectively called leatherjackets.
14 genera and about 33 species worldwide; 3 genera and 6 species in North America (5 Atlantic, 1 Pacific), plus 1 species confined to Mexican Pacific waters. Boxfished occur in tropical to warm-temperate seas throughout the world, where they frequent shallow coral reefs and rocky or sandy and grassy areas to depths of about 270' (82 m). The family takes its common name from the immovable protective carapace (a shell formed of modified scales) that almost completely encloses these small, slow moving fishes. The carapace has an opening for the mouth, eyes, gill slits, and fins, leaving only the caudal peduncle unprotected. In some species, the two sides of the carapace are completely joined along the dorsal midline behind the dorsal midline behind the dorsal fin; in others, the carapace is incomplete behind the dorsal fin. Some species have horn-like spines on the head and on the rear underside of the body. Those with a bony projection above each eye are often known as cowfishes. Pelvic fins are absent. Certain boxfishes are highly prized as food in the Caribbean; however, some species are toxic.
19 genera and about 121 species worldwide; 3 genera and 12 species in North America (9 Atlantic, 2 Pacific, 1 shared), plus 1 genus and 4 species confined to Mexican Pacific waters. Puffers are found in tropical to temperate marine and fresh waters throughout the world; the majority are marine. As the common name implies, these fishes are capable of rapidly inflating their bodies with either water or air. Most species are drably colored on the back, with various markings, and are silvery or white on the sides and the belly. The head is moderately pointed, with the eyes high on the sides. The mouth is terminal, and there are two teeth in each jaw. Pelvic fins are absent; the broad pectoral fins are well developed. The short-based dorsal and anal fins are located posteriorly. Puffers are unscaled, but some have spiny prickles, and some have small fleshy flaps on the sides. Some species are toxic.
6 genera and 19 species worldwide; 2 genera and 7 species in North America (4 Atlantic, 1 Pacific, 2 shared). These small to medium fishes are found in tropical waters throughout the world. Like the members of the related puffer family (Tetraodontidae), porcupinefishes are capable of rapidly inflating their bodies with either water or air. They are quite robust and covered with spines. The spines either resemble erectile quills with two-rooted bases (genus diodon), or they are stout and immovable with three-rooted bases (genus Chilomycterus); the bases are visible only when the skin is removed. There is a single tooth in each jaw; the teeth are fused at the midline, forming a parrot-like beak. Pelvic fins are absent, and the pectoral and caudal fins are well developed. The dorsal and anal fins are short-based.
3 genera and 3 species worldwide; all found in North America (1 Atlantic, 2 Atlantic and Pacific). These distinctive and unusual fishes occur in tropical to subtropical seas throughout the world. They have a very deep and compressed body; the posterior portion of the body looks as though it has been cut off. The snout is short and blunt, and the mouth is very small. The gill opening is reduced to a small, round to oblong pore. Molas have very short-based. The caudal fin is reduced to a feathery flap, exept in Sharptail Mola (Mola lanceolata)
