Masu salmon redds constructed in a straight-line river channel: a case study in the Akka River, Iwate Prefecture, Japan

Abstract

The distribution patterns of masu salmon redds were surveyed in Akka River, Iwate Prefecture, Japan from 2015 to 2018. Contrary to previous studies on spawning habitat preference of salmonid species, our results show that masu salmon redds tended to be constructed at straight-line stream channel. For the masu salmon, current velocity and water depth at the straight section might be suitable for redd construction in Akka River. In order to enhance fisheries resources through natural reproduction and hatchery programs, understanding the relationship between stream morphology and spawning habitat preference of target species is required for each population.