American Eel
  • Side view adult.
  • Side view adult.
  • Side view adult.
  • Top view of adult.
  • Bottom view of adult.
  • Head-on view (juvenile).
  • Close-up flank.
  • Close-up head.
  • Close-up mouth and snout.
  • Close-up tail.
  • Close-up dorsal fin.
  • Close-up anal fin.
  • Close-up pectoral fin.
  • Note gill slit at base of pectoral fin.
  • Jaws.
  • The body shows an elongated shape; pelvic fins are lacking; the dorsal and anal fins are continuous with tail.
  • The flank shows small, inconspicuous, embedded scales.
  • Juvenile specimen in hand.
  • Close-up of juvenile head: Juveniles are similar to adults.
  • Side view of juvenile: Juveniles are similar to adults.
DescriptionSimilar Species
Family
Freshwater Eels (Anguillidae)
Body
Mouth and Snout: The mouth is terminal and fairly large. Eels have jaws with teeth. No barbels. Body Pattern: The body and fins are solid dark brown or dark olive with no patterning on back grading to a dull yellow, cream or white on belly. Cycloid scales are extremely tiny and numerous. Body Shape: Elongate, flexible, snake-like body. In Wisconsin waters, typically 350-1000 mm TL, with a maximum size of 1100 mm (3 feet).
Fins
Tail rouned and continuous with long (greater than half the body length) single dorsal and anal fins that lack spines. There are no pelvic fins. No adipose fin.
Distinguishing Characteristics
The eel has a long, flexible body and no pelvic fins. It also has a terminal mouth with teeth in jaws. No pelvic fins, dorsal and anal fins long (longest ray much shorter than length of fin base) and continuous with caudal fin. Single small gill slit at base of pectoral fin, and body covered with small, inconspicuous, embedded scales. Distinctive Features: Elongate, flexible, snake-like body. See also similar species information.
Breeding Adults
The appearance of breeding fish is similar to nonbreeding adults. This species spawns in the ocean. Only females are found in Wisconsin; males remain in the lower reaches of coastal tributaries. The body color is more silver or gray during migration to the ocean, but this silver eel form is not known with certainty from Wisconsin.
Juveniles
Juveniles exist in a larval form (leptocephalus) that is not found in Wisconsin. These fish spawn in the Sargasso Sea, which is east of Florida and the Bahamas, and make a 3,000 mile migration to Wisconsin via the Mississippi River or the Great Lakes. The larval form is transparent, shaped like a leaf, and never occurs in freshwaters.
Hybrids
None known from Wisconsin.
Compare Similar Species
Body Shape
Eel, Americanelongated, flexible, snake-like
Lamprey, American Brookelongated, but not snake-like
Lamprey, Chestnutelongated, but not snake-like
Lamprey, Northern Brookelongated, but not snake-like
Lamprey, Seaelongated, but not snake-like
Lamprey, Silverelongated, but not snake-like
Lamprey, Southern Brookelongated, but not snake-like
Mouth/Teeth
Eel, AmericanTerminal mouth with teeth in jaws
Lamprey, American BrookSucking disk or flexible filtering "hood" instead of jaws
Lamprey, ChestnutSucking disk or flexible filtering "hood" instead of jaws
Lamprey, Northern BrookSucking disk or flexible filtering "hood" instead of jaws
Lamprey, SeaSucking disk or flexible filtering "hood" instead of jaws
Lamprey, SilverSucking disk or flexible filtering "hood" instead of jaws
Lamprey, Southern BrookSucking disk or flexible filtering "hood" instead of jaws
Pectoral Fin
Eel, AmericanPresent
Lamprey, American BrookAbsent
Lamprey, ChestnutAbsent
Lamprey, Northern BrookAbsent
Lamprey, SeaAbsent
Lamprey, SilverAbsent
Lamprey, Southern BrookAbsent
Gills
Eel, AmericanSingle small gill slit
Lamprey, American BrookSeven conspicuous circular gill openings
Lamprey, ChestnutSeven conspicuous circular gill openings
Lamprey, Northern BrookSeven conspicuous circular gill openings
Lamprey, SeaSeven conspicuous circular gill openings
Lamprey, SilverSeven conspicuous circular gill openings
Lamprey, Southern BrookSeven conspicuous circular gill openings
Scales
Eel, AmericanSmall, inconspicuous, embedded scales
Lamprey, American BrookNo scales
Lamprey, ChestnutNo scales
Lamprey, Northern BrookNo scales
Lamprey, SeaNo scales
Lamprey, SilverNo scales
Lamprey, Southern BrookNo scales
Similarity Index
Eel, AmericanN/A
Lamprey, American BrookSlightly similar
Lamprey, ChestnutSlightly similar
Lamprey, Northern BrookSlightly similar
Lamprey, SeaSlightly similar
Lamprey, SilverSlightly similar
Lamprey, Southern BrookSlightly similar
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