Distribution and Abundance of Juvenile Chum Salmon (Oncorhynchus keta)

Catches of chum salmon in Hokkaido increased after the 1970s and have remained over 30 million since the 1990s (Mayama and Ishida 2003). However, there are large differences in the amount of chum salmon catch among regions of Hokkaido (Saito and Nagasawa 2009; Nagata et al. 2012a, b). In the Nemuro region, catches of chum salmon constitute about 30 % of the total catch in Hokkaido, however, the catches in the northern and southern areas differ (Fig. 1). Although the number of juvenile chum salmon released in both areas is almost the same, the catch in the southern area is about onethird the catch in the northern area. Mortality of juvenile chum salmon in coastal waters just after entering the sea is thought to be higher than during othe