Impacts of Climatic Change and Fishing on Pacific Salmon Abundance Over the Past 300 Years

Abstract

The effects of climate variability on Pacific salmon abundance are uncertain because historical records are short and are complicated by commercial harvesting and habitat alteration. We use lake sediment records of delta15N and biological indicators to reconstruct sockeye salmon abundance in the Bristol Bay and Kodiak Island regions of Alaska over the past 300 years. Marked shifts in populations occurred over decades during this period, and some pronounced changes appear to be related to climatic change. Variations in salmon returns due to climate or harvesting can have strong impacts on sockeye nursery lake productivity in systems where adult salmon carcasses are important nutrient sources.

Nonlinear dynamics in ecosystem response to climatic change: Case studies and policy implications

“…Significant and coherent linkages between shifts in North Pacific Ocean physical and atmospheric conditions and a marine biological response in Alaskan salmon are well documented (Beamish and Bouillon, 1993;Francis and Hare, 1994;Mantua et al, 1997;Finney et al, 2000). Climate prediction models and our understanding of the mechanisms linking salmon and climate response in the North Pacific Ocean continue to improve as we learn more about the biological response of Pacific salmon to environmental variation and as our long-term data records on ocean condition and salmon production increase (Beamish et al, 1999).…”

Impact of climate change and human-mediated introgression on southern European Atlantic salmon populations

“…Finney et al, 2000;McFarlane et al, 2000, MacKenzie & Koster 2004. Among the species potentially sensitive to global warming (De Young et al, 2004), the migratory Atlantic salmon (Salmo salar, Salmonidae) provides an opportunity for a case study because of its broad distribution on both sides of the Atlantic Ocean and its sensitivity to environmental effects, particularly temperature (Mills, 1991).…”

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

“…The d 15 N values averaged 4.7% throughout the dated portion of the core, which is substantially higher than in salmon-free control lakes and generally consistent with expected values for similar spawning densities, suggesting that variation in d 15 N was related to MDN input (Finney et al 2000;Rogers et al 2013). For the first 1900 years (* 2000 BCE to 100 BCE) of the * 4000-year time series represented in the core, d 15 N averaged 4.9% (Figs.…”

“…1; 60.339°N, 149.880°W) because it is the Kenai River Watershed's most productive clear-water sockeye salmon nursery lake Willette 2011, 2014) and because its relatively high escapement density (* 20,000 spawners/km 2 ) makes it amenable to paleolimnological reconstruction of salmon abundance (Finney et al 2000). Upper Russian Lake is a relatively small lake (4.6 km 2 ) drained by the Russian River, which in turn flows into the Kenai River 119 km upstream from its mouth at Cook Inlet.…”

“…Paleolimnological analyses have led to reconstructions of sockeye salmon (Oncorhynchus nerka) abundance spanning hundreds or thousands of years in many nursery lakes (Finney 1998(Finney , 2000(Finney , 2002Gregory-Eaves et al 2003;Rogers et al 2013). These insights are possible because adult sockeye salmon, after gaining nearly all of their body mass at sea, return to natal river systems where they spawn and die, primarily in lakes and associated feeder streams.…”