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American Eel | Daily Animal Facts

Animal profile

American Eel

Anguilla rostrata

ActinopterygiiRivers, lakes and estuaries of the Atlantic coast of the Americas, with a marine spawning area in the Sargasso SeaEndangered

Field profile

The American eel occupies an unusually wide range of fresh, brackish and coastal waters for a single species. All individuals are thought to spawn in the Sargasso Sea, so the entire species behaves as one interbreeding population. Sex is not fixed at hatching.

Scope note

This is an editorial profile, not a diagnostic field-identification guide or a substitute for current conservation assessments. Follow the cited sources on each fact for the evidence trail.

Published field notes

2025-11-22

American Eel

An eel's sex is decided after it arrives

American eels do not hatch male or female. Sex is determined during the freshwater growth phase, and density is the strongest known influence: crowded, downstream habitats tend to produce males, while sparse upstream ones tend to produce females.

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