Title Biological characteristics of chum salmon in Japan
Authers Toshihiko SAITO, Yasutaka OKAMOTO, and Kei SASAKI
Keywords life-history trait, latitudinal gradient, regional difference, river stock, artificial propagation
Citation Bull. Fish. Res. Agen. No.39, 85-120, 2015
Abstract
To clarify the regional differences in biological characteristics of chum salmon, Oncorhynchus keta, inhabiting the northern Japan, the number of adult returns (coastal and river catches), peak of upriver migration (PUM), coastal sea surface temperature at the PUM, fork length of age 4 adults, age at maturity, egg diameter and fecundity of age 4 females were examined, on the basis of data collected in seven regions of northern Japan during the summerwinter of fiscal year 1994-2008. All biological characteristics showed clear differences among the regions or between some pairs of the ones, and some characteristics of river stocks appeared to change along latitudinal gradients. Particularly, the PUM, fork length, age at maturity, and egg diameter in river stocks along the Sea of Japan coast exhibited an abrupt change at the boundary of the Tsugaru Strait. In Hokkaido, the PUM was earlier as compared with previous observations made before 1960s, which probably resulted from artificial alterations of the run timing in many stocks. Consequently, the advanced PUM enforced fish to experience higher sea temperatures during their spawning migration. Egg diameter, standardized by grand mean of fish length of each stock, demonstrated a decreasing trend over the study period, although it was undeniable that a problem of the dataset might cause an apparent trend. Although some artificial alterations were recognized in biological characteristics of chum salmon stocks, this study demonstrated that regionally distinguishable traits are still present over the wide range of stocks in Japan.
URI http://www.fra.affrc.go.jp/bulletin/bull/bull39/39-06.pdf