Fat content as a factor inducing migratory behavior in the eel (Anguilla anguilla L.) to the Sargasso Sea

摘要: The eel, which is one of the few obligatory catadromous fish found at high latitudes [1], has a unique life cycle. The planktonic marine stage (Leptocephalus larvae) of the eel is relatively short (2-3 years) compared with its total life-span. The larvae drift from the presumed spawning areas in the Sargasso Sea to the coasts of Europe. Upon arrival at the coastal areas the larvae metamorphose into glass-eels, which are small and transparent, but have the shape of the adult. As the glass-eel migrates upstream the rivers it develops pigmentation, turning black with a yellowish abdomen. Most (> 90%) of the eels migrating upstream are juvenile females. The majority of males inhabit coastal waters. Sex-related differences in habitat choice are especially pronounced at higher latitudes [2]. At maturity, females are larger than males. The female eels remain in freshwater for 10-20 years, after which they stop feeding and return …