Role of a riverine plume as a nursery area for chum salmon Oncorhynchus keta

Abstract

We examined the spatial distribution of juveniles in coastal water to assess how riverine plumes serve as nursery areas for chum salmon in early ocean life. The distribution of juveniles was restncted withln a low-salinity water mass that was formed by nverine discharges. We detected 2 juvenile sizes at which distributions changed. Distributions of small juveniles (550 mm in fork length) and medium-size juveniles (50 to 75 mm) were found in nearshore reglons and were less affected by water temperature and salinity. Distributions of large juveniles (>75 mm) were located in waters whose salinity was 25 to 30 psu, and were less-affected by the distance from the shoreline. Results suggested that the juvenile distribution was affected by tolerance to environmental stress (high temperature or high salinity) and by refuge from fish predators. Juvenile chum salmon can use riverine plume habitats to avoid environmental stress, to search for prey patches, and to expend less energy for migration.