Sexual Dimorphism in the Adipose Fin of Pacific Salmon (Oncorhynchus)

Abstract

Male adipose fins of Oncorhynchus species were 30–50% larger than those of same-sized females, the actual amount depending on the species. Accuracy of classification of the standards ranged from 87% in chinook salmon (O. tshawytscha) to 98% in pink salmon (O. gorbuscha). Testing the method on new samples usually resulted in an accuracy of at least 90% correct identification of sex for any species. Relative size of the adipose fin should allow for easy and accurate external identification of the sexes of silver-bright Oncorhynchus.