National Geographic : 1954 Mar
400 Silver Sides Gleaming, Hungry Fish Flash Through the Photographer's Light Seen under the boat's electric lamp, tiny organisms swarmed in the water like dust motes in a sunbeam. At the bottom of the sea's eat-or-be-eaten food chain, such plankton fell prey to small herringlike fishes like these. They in turn disappeared down the maws of bigger fishes lurking in the shadows. would metamorphose into real eels, larvae of this type were for years considered a distinct species unrelated to the adult eel. They had their own scientific name, Leptocephalus. We caught at least three different types of leptocephali. Some individuals were flat, some wholly snakelike, some had an enigmatic single red dot, said to be the spleen, in the otherwise glassy abdominal region. Dane Tracked Down Eel Birthplace The man who first cracked the riddle of the eel's origin was Johannes Schmidt, a Danish marine specialist. His painstaking studies of the world-wide distribution of lepto cephali pointed, unexpectedly, away from con tinental waters and, instead, toward the south west Atlantic as the birthplace and cradle of leptocephali. Although full details are still lacking, we now know the highlights of the life story of the common eel. After a growth period of between 5 and 10 years, or even longer, in rivers and coastal waters of the continents, the mature eels return to the deep ocean. They migrate several thousand miles to the Sargasso Sea, a great area of the warm At lantic lying between Bermuda and the West Indies and fed by eddies from the Gulf Stream. There the returning eels descend to a considerable but yet undetermined depth, deposit their eggs, and then apparently die. The eggs hatch into transparent lepto cephali, which soon set out on their long predestined journey to the rivers and estuar ies of Europe, North America, and perhaps Africa. Those bound for Europe face a 21/2 year trip, those to North America a journey of less than a year, during which time they feed and grow. By the time of arrival at their destinations they are about to enter an other metamorphic phase, the elver stage. In this form they move into the rivers to grow into the common eel, so important for food in many European countries. Now the sexes separate. The males pre fer the brackish water of river mouths and estuaries; the females go far upstream.