Perspectives on wild and hatchery salmon interactions at sea,potential climate effects on Japanese chum salmon,and the need for sustainable salmon fishery management reform in Japan |
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Authors: | Masahide Kaeriyama Hyunju Seo Hideaki Kudo Mitsuhiro Nagata |
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Institution: | (1) Faculty of Fisheries Sciences, Hokkaido University, Hakodate Hokkaido, 041-8611, Japan;(2) Salmon and Freshwater Fisheries Institute, Eniwa Hokkaido, 061-1423, Japan |
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Abstract: | Pacific salmon (Oncorhynchus spp.) play an important role as a keystone species and provider of ecosystem services in the North Pacific ecosystem. We
review our studies on recent production trends, marine carrying capacity, climate effects and biological interactions between
wild and hatchery origin populations of Pacific salmon in the open sea, with a particular focus on Japanese chum salmon (O. keta). Salmon catch data indicates that the abundance of Pacific salmon increased since the 1976/77 ocean regime shift. Chum and
pink salmon (O. gorbuscha) maintained high abundances with a sharp increase in hatchery-released populations since the late 1980s. Since the 1990s,
the biomass contribution of hatchery returns to the total catch amounts to 50% for chum salmon, more than 10% for pink salmon,
and less than 10% for sockeye salmon (O. nerka). We show evidence of density-dependence of growth and survival at sea and how it might vary across spatial scales, and we
provide some new information on foraging plasticity that may offer new insight into competitive interactions. The marine carrying
capacity of these three species is synchronized with long-term patterns in climate change. At the present time, global warming
has positively affected growth and survival of Hokkaido populations of chum salmon. In the future, however, global warming
may decrease the marine carrying capacity and the area of suitable habitat for chum salmon in the North Pacific Ocean. We
outline future challenges for salmon sustainable conservation management in Japan, and recommend fishery management reform
to sustain the hatchery-supported salmon fishery while conserving natural spawning populations. |
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