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September 2009 cover image hunting dog

Wild Thing: American Eel

The strange life cycle of a (mostly) freshwater eel.

By Sheryl Smith-Rogers

Three years ago, Jennifer Bixby fought hard to reel in her fishing line at a Port Lavaca pier. “I was ready to cut it,” she recalls. Then, unexpectedly, she landed her catch — a slimy, serpentine American eel (Anguilla rostrata).

“I’d never caught one before nor seen one either, but I knew what it was from my college classes,” Bixby says of the fish species. Nowadays, she’s got another eel in her life. This one lurks in a saltwater exhibit at Sea Center Texas, where she works as a hatchery biologist.

Pulled from Galveston Bay's brackish waters, the male eel someday would have migrated back to the faraway Sargasso Sea northeast of Bermuda. Why? Amazingly, all American eels end their complex, often lengthy life cycle where they began.

No one’s ever documented their breeding behaviors, but biologists believe that American (and European) eels die soon after spawning in the Sargasso Sea. The transparent larvae (called leptocephali) drift with ocean currents and morph into “glass” eels. For a year or so, the transparent juveniles float until they reach coastal waters, which can be anywhere from Greenland to Brazil (including the Gulf Coast).

Moving into estuaries and rivers, the grayish or greenish “elvers” turn into sexually immature “yellow” adults. (Before modern dams, American eels once ranged upstream as far as New Mexico and the Red River.) Hiding under rocks by day, eels feed at night on fish, fish eggs, worms, clams and frogs. At maturity, females can measure 3 to 4 feet long and weigh 4 to 5 pounds whereas males generally reach 1.5 feet long and 3 pounds.

American eels are North America’s only catadromous species, meaning they live in freshwater but spawn in the ocean. (The life cycle of anadromous fish, like salmon, goes the other way.) After three or as many as 30 years, the eels turn “silver.” This final stage readies them for ocean travel with enlarged eyes, ample reserves of fat and a thicker, darker skin.

Finally, off they go, headed back to the Sargasso Sea to complete their life cycle — unless they happen onto someone’s fishing line.

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