DISTINGUISHING FEATURES OF NORTH AMERICAN FISH FAMILIES

 

 

 

1. Petromyzontidae ‑ (lampreys) eel‑shaped bodies; sucking‑disc mouth with teeth; jaws absent; pectoral and pelvic fins absent; seven external gill openings on each side.

 

2. Acipenseridae ‑ (sturgeons) caudal fin heterocercal; 5 rows of bony scutes on body (1 dorsal, 2 lateral, 2 ventral); mouth ventral and protractile; 4 barbels anterior to mouth; jaws toothless.

 

3. Polyodontidae ‑ (paddlefish) caudal fin heterocercal, no bony scutes; snout elongated in shape of paddle; body naked or with sparse scales; mouth non‑protractile and entirely behind eye; 2 barbels; jaws with small teeth.

 

4. Lepisosteidae ‑ (gars) caudal fin abbreviate‑heterocercal; snout very elongated with sharp teeth; external nares at tip of snout; scales thick and diamond‑shaped (ganoid) and not overlapping.

 

5. Amiidae ‑ (bowfin) caudal fin abbreviate‑heterocercal; scales cycloid, dorsal fin extremely long with 40 or more fin rays; underside of head with large, bony gular plate.

 

6. Anguillidae ‑ (eels) body long and slender; jaws present; pelvic fins absent; dorsal, caudal and anal fins continuous as a median fin fold;     opercular opening a small slot at base of rounded pectoral fins; scales minute and embedded deeply in skin.

 

7. Clupeidae ‑ (herring, shad) body deep and laterally compressed; midline of belly with a sharp keel formed of modified scales; axillary process (small scale projection at upper surface of pelvic fin) present; principal anal fin rays 17 or more; dorsal fin ahead of anal fin; teeth absent in adult; gill openings extending forward on throat to beneath eye; lateral line absent or much reduced, scales with circuli running more or less vertically rather than concentrically.

 

8. Salmonidae ‑ (salmon, trout, whitefish, grayling) adipose fin present; axillary process of pelvic fins present; spires in fins absent; lateral line scales more than 100, at least in the subfamily Salmonidae (trout, salmon charrs). If scales in lateral line less than 100, then jaws lack teeth.

 

9. Esocidae ‑ (pikes and pickerels) snout moderately elongated with large number of teeth; dorsal and anal fins situated far back on body; daudal fin forked; scales present on sides of head; lateral line scales more than 95; scale cycloid; no spines; ventral fins abdominal.

 

10. Cyprinidae ‑ (minnows, chubs, shiners) jaws without true teeth; pharyngeal teeth present; Weberian apparatus present; adipose fin absent; spines absent; air bladder divided into two parts, ventral fins abdominal; distance from front of anal fin to base of caudal fin going less than 2 1/2 times into distance from front of anal fin to tip of snout.

 

 

11. Catostomidae ‑ (suckers, carpsuckers) Weberian apparatus present; jaws without teeth; pharyngeal teeth present; adipose fin absent; ventral fins abdominal; spines absent; mouth ventral with sucking lips (don't be completely "sucked in" by this usually reliable character); distance from front of anal fin to base of caudal fin going more than 2 1/2 times into distance from front anal fin to tip of snout.

 

12. Ictaluridae ‑ (catfish) Weberian apparatus present; jaws without teeth; pharyngeal teeth present; adipose fin present; body scaleless; dorsal and pectoral fins with a stout spine; large barbels near mouth.

 

13. Fundulidae ‑ (Topminnows) small fishes less than 4 inches usually; ventral fins abdominal with not more than 7 rays; single dorsal and anal fin usually far back on body more or less opposite and equal and rounded; fins without spines; head scaly; no lateral line; caudal fin rounded or square but never forked; third anal ray branched; egg layers.

 

14. Poeciliidae ‑ (Livebearers, Topminnows) small fishes less than 4 inches usually; ventral fins abdominal with not more than 7 rays; single dorsal and anal fin usually far back on body more or less opposite and equal and rounded; fins without spines; head scaly; no lateral line; caudal fin rounded or square but never forked; third anal ray unbranched; anal fin of male modified as an intromittent organ; gives birth to live young.

 

15. Atherinidae ‑ (silverside) long slender fishes; dorsal fin double with first dorsal possessing 4‑5 weak spines; pectoral fins located high on body; base of pelvic fin closer to front of anal fin than to hind margin of gill cover; pelvic fins I, 5; anal fin I, 20+.

 

16. Moronidae ‑ (Basses) dorsal fin double (or nearly so) with more than 6 spines; pelvic fins I, 5; anal fin with 3 or more spines, free margin of preopercle strongly serrate, serrate.

 

17. Centrarchidae ‑ (freshwater basses, crappies, sunfishes) dorsal fin single with more than 6 spines; pelvic fins I, 5; anal fin with 3 or more spines;free margin of preopercle usually smooth.

 

18. Percidae ‑ (walleyes, perch) dorsal fin double with more than 6 spines; pelvic fins I, 5; anal fin with 1 or 2 spines; soft dorsal fin not longer than spinous dorsal with fewer than 23 rays; second spine of anal fin, if present slender and not much longer than first; lateral line not extending onto caudal fin.

19. Sciaenidae ‑ (freshwater drum) pelvic fin I, 5, anal fin II, 7‑8; dorsal fin single but slightly notched with 10 spines and 31‑32 soft rays; second spine of anal fin much stouter than first; lateral line extending onto caudal fin.

 

 

20. Cottidae ‑ (sculpins) pectoral fins much expanded; body without scales; dorsal fin with more than 6 spines; pelvic fin I 3‑4; no anal spines.

 

2l. Hiodontidae ‑ (mooneyes) body laterally compressed with belly possessing a keel, but no scutes. Lateral line present; mouth with teeth; axillary scale present on pelvic fins. Dorsal fin positioned over anal fin; eyes proportionally large.

 

22. Umbridae ‑ (mudminnows) ventral fins abdominal, fins without spines, caudal fin rounded or truncate, head partially scaled, mesocoracoid absent, dorsal fin posterior, scales cycloid. Pectoral radials ossified. Pectoral rays 12‑16.

 

23. Dalliidae ‑ (Alaska Blackfish) ventral fins abdominal, fins without spines,caudal fin rounded, head partially scaled, mesocoracoid absent, dorsal fin posterior, scales cycloid, pectoral radials not ossified, pectoral rays 33‑37.

 

24. Characidae ‑ (characins) adipose fin present. Weberian apparatus present. Strong teeth in jaws. Pseudobranchiae absent. Body often deeply laterally compressed.

 

25. Gadidae ‑ (cods) ventral fins jugular with many rays. Single mental barbel. 2‑3 dorsal and 1‑2 anal fins. Tail isocercal and rounded. No spines in fins. Scales cycloid. Scales present but small.

 

26. Percopsidae ‑ (Troutperch) single dorsal fin. Adipose fin present. Caudal fin deeply forked. Ctenoid scales. Anal and dorsal fins with one or more weak spines.

 

27. Aphredoderidae ‑ (Pirate Perch) single dorsal fin and ctenoid scales. Anus in throat region. Gill cover with a sharp spine. preopercle strongly serrate. Dorsal and anal fins with 2 or 3 weak spines. Lateral line absent or incomplete.

 

28. Embiotocidae ‑ (Surfperch) viviparous, spiny rayed fishes with small mouths, unarmed heads, and cycloid scales. Dorsal fin when depressed fits into a furrow.

 

29. Cichlidae ‑ (Cichlids) body laterally compressed as in the sunfishes. Dorsal fin single with spinous and soft portions, nostrils single. (In contrast to sunfishes).

 

30. Gasterosteidae ‑ (Sticklebacks) two or more free spines in front of dorsal fin. Ventral fins thoracic and composed of 1 large spine and 0‑2 rays. Pectoral fin positioned more posterior than usual in most fishes. Dermal bony plates on body.

 

31. Amblyopsidae ‑(cavefish family) anus thoracic in position, caudal fin rounded or truncated. Head often depressed. Spines absent in fins. Body often white in color. Eyes generally absent or reduced in size. Pelvic fins often absent.

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