Future of Pacific Salmon in the Face of Environmental Change: Lessons from One of the World's Remaining Productive Salmon Regions

Abstract

Pacific salmon Oncorhynchus spp. face serious challenges from climate and landscape change, particularly in the southern portion of their native range. Conversely, climate warming appears to be allowing salmon to expand northwards into the Arctic. Between these geographic extremes, in the Gulf of Alaska region, salmon are at historically high abundances but face an uncertain future due to rapid environmental change. We examined changes in climate, hydrology, land cover, salmon populations, and fisheries over the past 30–70 years in this region. We focused on the Kenai River, which supports world‐famous fisheries but where Chinook Salmon O. tshawytscha populations have declined, raising concerns about their future resilience. The region is warming and experiencing drier summers and wetter autumns. The landscape is also changing, with melting glaciers, wetland loss, wildfires, and human development. This environmental transformation will likely harm some salmon populations while benefiting others. Lowland salmon streams are especially vulnerable, but retreating glaciers may allow production gains in other streams. Some fishing communities harvest a diverse portfolio of fluctuating resources, whereas others have specialized over time, potentially limiting their resilience. Maintaining diverse habitats and salmon runs may allow ecosystems and fisheries to continue to thrive amidst these changes.

Sockeye salmon population dynamics over the past 4000 years in Upper Russian Lake, south-central Alaska

“…An unknown portion of the Russian River's late run has been harvested by Cook Inlet's commercial fisheries since they began, shown in recent years by genetic stock identification, to average 28% (2006-2008Eskelin et al 2013), so it is possible that commercial harvest has not impacted escapement enough to elicit the dramatic 15 N depletion seen in other systems. Harvest rates on Russian River salmon have presumably increased in recent decades (Schoen et al 2017), with the growth of sport fisheries that harvest approximately 50% of the early run and 29% of the late run and a personal-use fishery that harvests 7% of the late run (Begich and Pawluk 2007;Eskelin et al 2013;Fair et al 2013). This additional harvest may be too recent to be reflected in Upper Russian Lake sediments (Rogers et al 2013), especially given the relatively low temporal resolution of our core subsampling.…”

“…The Kenai River is the most productive sockeye salmon system in south-central Alaska's Cook Inlet Watershed, producing over half of the Inlet's average annual return of 5.2 million sockeye salmon (Willette and Shields 2015;Schoen et al 2017). The Cook Inlet commercial fishery harvests an average of 2.9 million sockeye salmon with an ex-vessel value of $26.3 million (1966-2014Shields and Dupuis 2016).…”

Fishing for conservation of freshwater tropical fishes in the Anthropocene

“…The river also supports Chinook ( Oncorhynchus tshawytscha ) and sockeye salmon ( Oncorhynchus nerka ) populations, and their anadromous migrations are vital to both freshwater and terrestrial ecosystems because of nutrient input from post‐spawning decomposition of their bodies (Gende, Edwards, Willson, & Wipfli, ). Salmon also have important socioeconomic value to local communities and the state of Alaska by supporting commercial and sport fisheries worth over a billion US dollars annually (Schoen et al, ). Alaskan salmon have a strong cultural value as an important food source for many subsistence fishers.…”

Hydrologic Resilience from Summertime Fog and Recharge: A Case Study for Coho Salmon Recovery Planning

“…Warming due to climate change has exacerbated the ongoing decline of salmonids by rendering stretches of instream habitat thermally unsuitable (Isaak et al 2012;Lawrence et al 2014;Ward et al 2015;Schoen et al 2017). The CCC coho is one of the salmon species in precipitous decline, in danger of extinction (NMFS 2012c; Katz et al 2013), and highly sensitive to water temperature and streamflow (Grantham et al 2012;Arismendi et al 2013;Flitcroft et al 2016).…”