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On the sex and distribution of the freshwater eel (Anguilla anguilla)
Author(s) -
Jones V. R. P. Sinha AND J. W.
Publication year - 1966
Publication title -
journal of zoology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.915
H-Index - 96
eISSN - 1469-7998
pISSN - 0952-8369
DOI - 10.1111/j.1469-7998.1966.tb03012.x
Subject(s) - biology , gonad , fish <actinopterygii> , brackish water , fish migration , sex ratio , zoology , freshwater fish , fresh water , fishery , ecology , demography , anatomy , population , salinity , sociology
This paper reports the result of an examination of about 8000 eels mainly from various parts of several Welsh rivers made to try and find out whether the distribution of eels was determined by their sex. Contrary to the popular belief, males and females were found living together in freshwater and in brackish water. The organ of Syrski, which was supposed to be diagnostic of the male sex has been found ambiguous in nature and not always a precursor of a male gonad. The consequent difficulties of the identification of the sex of moderately sized eels is discussed and it is suggested that the abnormal sex ratio, as reported by some investigators, is related to the obscure structure of the organ of Syrski and the fact that gonad differentiations may not occur until the fish is quite large. The possibility that other factors such as selective fishing and a sex differential in growthrates and duration of freshwater life may also be contributory factors isdiscussed. It is suggested that the environment plays little part in sex determination.