Background
The authors write that "Pacific salmon (Oncorhynchus spp.) play an important role as both keystone species in North Pacific ecosystems and as an ecosystem service that provides human food resources for countries of the North Pacific rim," citing Kaeriyama (2008); and they note that the Hokkaido chum salmon (O. keta) experiences a period of critical mortality that "is characterized by size-dependent mortality and size-selective predation, immediately after seaward migration," citing the work of Healey (1982), Kaeriyama (1986), Kaeriyama and Ueda (1998) and Kaeriyama et al. (2007)."

What was done
In an effort to determine the effect of global warming on this critical mortality period in the life of Hokkaido chum salmon, Seo et al. used multiple regression and path analysis to examine the effects of regional and larger spatial scales of climatic/oceanic conditions on the growth, survival and population dynamics of the species.

What was learned
The three researchers, all of them with the Faculty of Fisheries Sciences at Japan's Hokkaido University, determined that growth of one-year-old chum salmon in the Okhotsk Sea "was less during the period from the 1940s to the mid-1970s compared to the period from the mid-1980s to the present," which result "was directly affected by warmer sea surface temperatures associated with global warming." And they add that "the increased growth at age one led directly to higher survival rates and indirectly to larger population sizes."

What it means
There's nothing like getting off to a good start in life, and in the case of Hokkaido chum salmon, that good start appears to be due to a good dose of late 20th century/early 21st century global warming.

References
Healey, M.C. 1982. Timing and relative intensity of size-selective mortality of juvenile chum salmon (Oncorhynchus keta) during early sea life. Canadian Journal of Fisheries and Aquatic Sciences 39: 952-957.

Kaeriyama, M. 1986. Ecological study on early life of the chum salmon, Oncorhynchus keta (Walbaum). Scientific Reports of the Hokkaido Salmon Hatchery 40: 31-92.

Kaeriyama, M. 2008. Ecosystem-based sustainable conservation and management of Pacific salmon. In: Tsukamoto, K., Kawamura, T., Takeuchi, T., Beard Jr., T.D. and Kaiser, M.J. (Eds.) Fisheries for Global Welfare and Environment. TERRA-PUB, Tokyo, Japan, pp. 371-380.

Kaeriyama, M. and Ueda, H. 1998. Life history strategy and migration pattern of juvenile sockeye (Oncorhynchus nerka) and chum salmon (O. keta) in Japan: a review. North Pacific Anadromous Fish Commission Bulletin 1: 163-171.

Kaeriyama, M., Yatsu, A., Noto, M. and Saitoh, S. 2007. Spatial and temporal changes in the growth patterns and survival of Hokkaido chum salmon populations in 1970-2001. North Pacific Anadromous Fish Commission Bulletin 4: 251-256.