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Science Frontiers ONLINE No. 79: Jan-Feb 1992 |
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Those slippery (adult) eels
Every year untold millions of adult eels swim down the rivers of the continents toward the sea, where they are literally swallowed up. They are never seen again! In the Atlantic, the oft-told sci-entific tale is that all the adult eels from Europe and eastern North America converge on the Sargasso Sea. Here, they mate and die. It is in this area of the Atlantic that one finds high concentrations of eel larva, called leptocephali; and this alone is why the eels are thought to spawn here.
In a long article in Science News, E. Pennisi is the latest to wonder where the adult eels are. She relates how, despite several ambitious expeditions well-armed with nets, traps, and sundry eel-catching devices, "...no one has ever spotted adult eels in the spawning grounds."
Actually, Pennisi's article focusses on the Pacific and a 1991 Japanese expedition that searched for the spawning grounds of Anguilla Japonica, the Japanese eel. Earlier searches had been in conclusive. The 1991 attempt, after arduous labors and 16,000 kilometers of cruising, found the highest concentrations of leptocephali east of the Philippines. But, as in the Atlantic, even though many larvae were captured, no adult eels turned up in the nets. (Pennisi, Elizabeth; "Gone Eeling," Science News, 140:297, 1991.)
Comment. It is our understanding that adult eels are never caught anywhere once they leave their home rivers. Can anyone refute this?