Title Status of hatchery production of chum salmon populations in Japan
Authers Masaya TAKAHASHI
Keywords artificial enhancement, egg reservation, coastal sea surface temperature, chum salmon, fry release, body size
Citation Bull. Fish. Res. Agen. No.39, 49-84, 2015
This review paper compared trends of artificial enhancement activities (timing of spawning operations, effective population size, timing of fry releases and body size of released fry) among seven regional populations of chum salmon (Okhotsk, Hokkaido Sea of Japan, Nemuro, East Hokkaido Pacific, West Hokkaido Pacific, Honshu Pacific, and Honshu Sea of Japan) in northern Japan. Seasonal changes of coastal sea surface temperature (SST) in each region were also compared. In 2010, a total of 246 chum salmon hatcheries was operated in northern Japan, and the mean number of fry releases per facility was 7,527 thousand fish. Relatively small hatcheries were abundant in the west Hokkaido Pacific and Honshu Sea of Japan regions. The timing of taking eggs peaked in late October for the Okhotsk and east Hokkaido Pacific populations, and late November for the Honshu Pacific population. The recent e f fe ct ive p opu l at ion s i z e (Ne) exceeded 10,000 adults/year in five river populations (Tokushibetsu, Ishikari, Nishibetsu, Tokachi, and Yurappu) representing each regional population in Hokkaido. Patterns of coastal SST changes during juvenile salmon migration varied among regions: SST increased faster in the Sea of Japan regions than in the Pacific regions. The peak of fry releases was almost stable in late March for the Honshu Sea of Japan population, and in late May for the Okhotsk population, but it fluctuated in other regional populations. The mean body size of released fry increased in three regional populations (Okhotsk, Hokkaido Sea of Japan, and East Hokkaido Pacific), but did not change in other regional populations since 1990s. Future issues to maintain Japanese chum salmon populations are: 1) well understanding the features of each regional population, 2) conserving the diversity of each population, and 3) identifying the best timing of fry releases and their body size in each population to maximize their survival in the ocean.
URI http://www.fra.affrc.go.jp/bulletin/bull/bull39/39-05.pdf