Non-stationary and interactive effects of climate and competition on pink salmon productivity

Jan Ohlberger; Eric J Ward; Richard E Brenner; Mary E Hunsicker; Stormy B Haught; David Finnoff; Michael A Litzow; Tobias Schwoerer; Gregory T Ruggerone; Claudine Hauri

doi:10.1111/gcb.16049

Non-stationary and interactive effects of climate and competition on pink salmon productivity

Glob Chang Biol. 2022 Mar;28(6):2026-2040. doi: 10.1111/gcb.16049. Epub 2021 Dec 24.

Authors

Affiliations

¹ School of Aquatic and Fishery Sciences, University of Washington, Seattle, Washington, USA.
² Conservation Biology Division, Northwest Fisheries Science Center, National Oceanic and Atmospheric Administration, Seattle, Washington, USA.
³ Division of Commercial Fisheries, Alaska Department of Fish and Game, Juneau, Alaska, USA.
⁴ Fish Ecology Division, Northwest Fisheries Science Center, National Oceanic and Atmospheric Administration, Newport, Oregon, USA.
⁵ Department of Economics, College of Business, University of Wyoming, Laramie, Wyoming, USA.
⁶ Alaska Fisheries Science Center, National Oceanic and Atmospheric Administration, Kodiak, Alaska, USA.
⁷ Institute of Social and Economic Research, University of Alaska Anchorage, Anchorage, Alaska, USA.
⁸ Natural Resources Consultants, Inc, Seattle, Washington, USA.
⁹ International Arctic Research Center, University of Alaska Fairbanks, Fairbanks, Alaska, USA.

Abstract

Pacific salmon (Oncorhynchus spp.) are exposed to increased environmental change and multiple human stressors. To anticipate future impacts of global change and to improve sustainable resource management, it is critical to understand how wild salmon populations respond to stressors associated with human-caused changes such as climate warming and ocean acidification, as well as competition in the ocean, which is intensified by the large-scale production and release of hatchery reared salmon. Pink salmon (O. gorbuscha) are a keystone species in the North Pacific Ocean and support highly valuable commercial fisheries. We investigated the joint effects of changes in ocean conditions and salmon abundances on the productivity of wild pink salmon. Our analysis focused on Prince William Sound in Alaska, because the region accounts for ~50% of the global production of hatchery pink salmon with local hatcheries releasing 600-700 million pink salmon fry annually. Using 60 years of data on wild pink salmon abundances, hatchery releases, and ecological conditions in the ocean, we find evidence that hatchery pink salmon releases negatively affect wild pink salmon productivity, likely through competition between wild and hatchery juveniles in nearshore marine habitats. We find no evidence for effects of ocean acidification on pink salmon productivity. However, a change in the leading mode of North Pacific climate in 1988-1989 weakened the temperature-productivity relationship and altered the strength of intraspecific density dependence. Therefore, our results suggest non-stationary (i.e., time varying) and interactive effects of ocean climate and competition on pink salmon productivity. Our findings further highlight the need for salmon management to consider potential adverse effects of large-scale hatchery production within the context of ocean change.

Keywords: climate; competition; density dependence; hatcheries; ocean acidification; population productivity; salmon.

MeSH terms

Animals
Climate
Fisheries
Humans
Hydrogen-Ion Concentration
Salmon*
Seawater*