From: familyman
Category: Fish Report
Date: 11/29/2004
Time: 12:20:14 PM
A long read, all you ever needed to know about eels...
Eels of the family Anguillidae, are freshwater and return to the ocean to spawn. These freshwater eels, which are the most important as food and are often sold live in markets, have dense capillary systems close to the skin that can absorb oxygen directly from air or water. The eels hatch from eggs as leptocephali, which are transparent, very thin, leaflike larvae bearing little resemblance to the adults. They drift about ocean surfaces for as long as three years, feeding on plankton, then metamorphose into round-bodied young eels called elvers, or grass eels, and begin to feed on fish, crabs, and other invertebrates until they reach full size.
The migration and reproduction of freshwater eels remained a mystery until the 20th century, when their spawning beds were discovered in the Sargasso Sea between Bermuda and Puerto Rico. When the very similar European eel, Anguilla anguilla, and the American eel, A. rostrata, reach maturity in freshwater lakes and rivers, they take watercourses, sometimes slithering overland through dewy grass, to reach the ocean, where they swim or drift with currents for as long as a year until they reach the sluggish, weed-filled Sargasso. Here the eels spawn in deep water, and, before dying, the female produces as many as 20 million free-floating eggs. The leptocephali drift with the Gulf Stream, taking one year to reach North America and three years to reach Europe. By this time they have become elvers and accumulate at the mouths of rivers in great masses. The yellow elvers swim upstream and feed on lake- and river-bottom animals until they become black-and-silver-bodied adults, completing the cycle.