American Eel

Fascinating facts about the American Eel

• A female American eel can dump up to 4 million buoyant eggs in the Sargasso Sea and then dies, while the biggest individuals may release as many as 8.5 million – a single reproductive burst that fuels the entire species for the next generation.
• From their birth in the Sargasso Sea, young eels drift westward on the Gulf Stream for 7–12 months, then travel as far as 6,000 km inland to freshwater habitats, a journey that can span many years before they return to spawn.
• An adult American eel can reach 1.22 m (4 ft) in length and weigh 7.5 kg (17 lb); across all life stages it carries a consistent vertebral count of about 107 (mean 107.2) and 108 myomeres, a skeletal fingerprint that sets it apart from its relatives.
• Stomach analysis of 169 eels showed that 99% had eaten macroinvertebrates, with the stonefly Acroneuria appearing in 67% of those guts, highlighting how these slim predators rely heavily on tiny insects during their nocturnal hunts.
• Hydroelectric dams have slammed the door on eel migrations, wiping out local populations in many watersheds; in Canada, once-abundant runs in the St. Lawrence and Ottawa Rivers have sharply declined as barriers block their upstream and downstream journeys.

At a glance

About the American Eel

The American eel (Anguilla rostrata) glides through North America’s waterways with a slender, snake-like body cloaked in a slippery mucus layer that hides its minute, irregularly arranged cycloid scales. Its long dorsal fin merges seamlessly with a similar anal fin, while tiny pectoral fins sit near the midline and pelvic fins are absent. Coloration shifts from olive-green and brown in tannic streams to lighter green-yellow or gray in clear water, and individuals can reach 1.22 m (4 ft) and 7.5 kg (17 lb), females typically outsize the males. By day they vanish into mud, sand or gravel at depths of about 5–6 ft (1.5–1.8 m), emerging at night to hunt a banquet of crustaceans, aquatic insects, small fish and mollusks, guided by an acute sense of smell. A surprising trait lies in their life-cycle: after a semelparous spawning plunge into the distant Sargasso Sea, a female may release up to 4 million buoyant eggs, then die, while the tiny leptocephalus larvae drift for months on the Gulf Stream before transforming into glass eels that climb inland streams, a journey that can span up to 6,000 km.

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