Changes in habitat use and preference by newly emerged masu salmon fry, Oncorhynchus masou, in Hokkaido streams

Abstract

Visual and electrofishing observations were conducted in the Atsuta and Shakotan rivers of Hokkaido to investigate changes in habitat use and preference for newly emerged masu salmon fry. Fry favored stream margins with shallow slow moving water, aquatic vegetation and large gravel. As fry grew and energetic requirements increased, they moved to new habitats with faster, deeper water, and less cover where food was presumably more abundant. To optimize growth and survival of young stream-rearing masu salmon, it is essential to restore and conserve stream margins with habitats suitable for these valuable fish.