Neo-Science of Natural History : Integration of Geoscience and Biodiversity Studies;Proceedings


Sexual Difference in Masu Salmon : Female-Biased Sexual Size Dimorphism in a Lacustrine Population, Northern Hokkaido, Japan

Tamate, Tsuyoshi

Permalink :
KEYWORDS : Body size;Sexual differences;Sexual size dimorphism (SSD)


To explore evolutionary processes of sex-specific traits, it is examined whether adult body size or growth during the migration phase (the lacustrine-phase after smolting) differ between the sexes in migratory (lake-run) masu salmon (Oncorhynchus masou) in a lacustrine population (Shumarinai Lake), northern Hokkaido, Japan. Although there was no difference in smolt length between the sexes, female adults were larger in body length than males of the same age, indicating female-biased sexual size dimorphism (SSD) occurs. It is supposed that breeding selection favouring a larger body size for females than for males in this population probably requires that females undertake more intensive foraging behaviour with faster growth rates during the migration phase. It therefore seems to be likely that the selection is the ultimate cause of the female-biased SSD.