How to Identify American Eel

To identify American Eel (Anguilla rostrata), look at these key features.

Physical Characteristics

Body shape

eel-like

Coloration

Varies significantly with life stage. Leptocephalus larvae are transparent and leaf-like. Glass eels are transparent. Elvers are pigmented but still translucent. Yellow eels (juvenile and adult freshwater stage) are typically olive-green to yellowish-brown dorsally, with a lighter, often yellowish, ventral surface. Silver eels (migratory adult stage) develop a darker, often blackish, dorsal surface and a silvery-white belly, with enlarged eyes.

Scale type

cycloid

Mouth position

terminal

Distinctive features

Elongated, snake-like body, Small, embedded scales (often not visible to the naked eye), Continuous dorsal, caudal, and anal fins, Prominent lower jaw, Small, rounded pectoral fins, Absence of pelvic fins

Dorsal fin

Long, continuous, originating far behind the pectoral fins and merging with the caudal and anal fins.

Tail fin

Rounded, confluent with the dorsal and anal fins.

Pectoral fin

Small, rounded, located just behind the head.

Distinctive fins

Absence of pelvic fins. The dorsal, caudal, and anal fins form a single, continuous fringe around the posterior half of the body.

Identification Tips

1. 1

   Body Shape

   Its distinctly elongated, snake-like body is the most obvious identifier. Unlike lampreys, eels have jaws and paired pectoral fins.

2. 2

   Fins

   The continuous dorsal, caudal, and anal fins forming a single fringe around the tail is characteristic. The absence of pelvic fins is also a key feature.

3. 3

   Scales

   While present, the scales are very small and deeply embedded in the skin, making the eel appear scaleless and feel slimy.

4. 4

   Mouth

   The lower jaw typically protrudes slightly beyond the upper jaw.

5. 5

   Coloration (Life Stage Dependent)

   Observe coloration to infer life stage: transparent (glass eel), yellowish-brown (yellow eel), or silvery-black (silver eel).

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