Temporal and Spatial Variations in Body Size of Chum Salmon in Hokkaido

Abstract Excerpt:
In Hokkaido, chum salmon (Oncorhynchus keta) is one of the most commercially important species. A decline in body size of Hokkaido chum salmon has been reported over the last century, and density-dependent growth had been suggested as a possible cause (Ishida et al. 1993; Kaeriyama 1998). Changes in body size relate to both behavioral and physiological traits such as survival, number of eggs per body, and mating success in many marine fish species. These changes may cause fisheries problems, one example being a reduction of recruitment. The coastal catch of chum salmon in Hokkaido has been decreasing in recent years, however, trends and geographic variation of decline are uncertain. To understand the biological condition deeply, we analyzed the changes in body size of chum salmon in Hokkaido.