Interspecific differences in the vertical distribution patterns of Sebastes inermis and S. ventricosus

Abstract

— Information on behavioral variation among sympatric congeneric species is important for understanding the mechanisms that enable their coexistence. The aim of this study was to elucidate the characteristics of diurnal vertical distribution of congeneric Sebastes inermis and S. ventricosus through observations during laboratory experiments in 2011. When 25 individuals of each species were accommodated in a 1-kL tank, S. inermis stayed mainly at the bottom, whereas S. ventricosus actively swam 0–60 cm above the bottom. At various intraspecific densities, S. inermis were similarly distributed at the bottom, S. ventri-cosus were distributed more widely, and the frequency of individuals in the upper layers of water in the tank increased with density. These results indicate that the different behaviors of the 2 species make their coexistence possible without severe competition for microhabitats.