Sex Ratio of American Eels, Anguilla rostrata, from the Matamek River System, Quebec, with Remarks on Problems in Sexual Identification

Abstract

The failure to examine gonadal tissue of American eels, Anguilla rostrata, histologically could result in considerable errors in sexual identification. Two "organs of Syrski", usually considered to be the male testes, and several small, ribbon-like gonads, generally thought to indicate female ovaries, revealed contradictory results when sectioned histologically. Other sources of error in determining a representative sex ratio of eels were noted. In the Matamek River system, Quebec, the range in length at which gonadal formation commenced was considerable. Male eels were rare (5 of 613 fish), which is consistent with other reports for the northern limits of this species.