Consequences of changing climate and geomorphology for bioenergetics of juvenile sockeye salmon in a shallow Alaskan lake

Abstract

– In high northern latitudes, a wide range of geomorphic processes associated with fluvial, glacial and permafrost activity may interact with climate change to produce unexpected changes in lake thermal regimes with attendant effects on ecological processes. We coupled output from a hydrodynamics model of lake thermal structure to a bioenergetics model to assess how alternative scenarios of climate change, geomorphic evolution and habitat restoration in a shallow Alaskan lake may affect juvenile sockeye salmon bioenergetics and growth. In particular, we evaluated the metabolic costs of different thermal regimes and the potential for changes in consumption to offset those costs. Increased water temperatures associated with future climate increased metabolic costs which were partially offset if fish were able to maintain feeding rates, expressed as a constant proportion of maximum consumption. In this lake, water levels have declined substantially in the last 50 years. Simulated restored lake level had negligible effects on lake temperature and thus on sockeye salmon growth when compared to current conditions. Maintaining lake connectivity to inlet tributaries (cooling lake temperature) was crucial in reducing sockeye salmon metabolic costs particularly with further drops in lake level and climate warming. While considerable research is focused on predicting future thermal and geomorphic conditions in aquatic ecosystems, these processes are rarely considered together, especially for lakes. Understanding the biological responses to geomorphic–climate interactions will be required for developing scenarios for coping with ecosystem responses to global change and evaluating restoration alternatives, especially in high‐latitude systems that support economically and culturally important fisheries.

Prey partitioning and use of insects by juvenile sockeye salmon and a potential competitor, threespine stickleback, in Afognak Lake, Alaska

“…In Black Lake, Alaska, chironomids of all life stages dominated the summer diets of juvenile sockeye salmon until August, after which they switched to zooplankton (Griffiths & Schindler, 2012;Ruggerone, 1994). In Black Lake, Alaska, chironomids of all life stages dominated the summer diets of juvenile sockeye salmon until August, after which they switched to zooplankton (Griffiths & Schindler, 2012;Ruggerone, 1994).…”

Climate variation is filtered differently among lakes to influence growth of juvenile sockeye salmon in an Alaskan watershed

“…The Black Lake stock's negative growth response to both spring and fall increases in air temperature is likely due to the high sensitivity of Black Lake water temperature to changes in air temperature (Griffiths et al 2011). In Black Lake, warmer than average months may have led to water temperatures (> 15°C if food is not limiting, Brett 1971) that increase metabolic stress for juvenile sockeye salmon (Griffiths and Schindler 2012, Griffiths et al 2011). There are not consistent records of Black Lake water temperature, but in 13 of the 15 years of data collected between 1991–2011 daily temperatures exceeded 15°C at least once during summer.…”

“…one or more summer growing periods, Groot and Margolis 1991) as well as overwinter (Quinn and Peterson 1996, Ebersole et al 2006) and marine survival (Koenings et al 1993). Climate conditions can affect juvenile salmon growth by altering the duration of the growing season (Schindler et al 2005), affecting metabolic and consumption rates (Griffiths and Schindler 2012), and altering the dynamics and production of prey resources (Winder and Schindler 2004, Hampton et al 2006, Carter and Schindler 2012).…”

How Stock of Origin Affects Performance of Individuals across a Meta-Ecosystem: An Example from Sockeye Salmon

“…We found no relationship between the proportion of Black Lake juvenile sockeye in Chignik Lake and either Black Lake temperature or the ratio of Black Lake to Chignik Lake adult spawners in the previous year. One hypothesis is that in warm years Black Lake is more stressful [59], which increases the downstream emigration rate. Similarly, greater competition during years of high densities in Black Lake could lead to increased emigration downstream.…”

“…In the Chignik watershed, it has become apparent that Black Lake, while a more productive habitat than downstream Chignik Lake, can become unfavorable for juvenile sockeye salmon as the growing season progresses [59], [63]; this effect is particularly pronounced when lake temperatures are warmer than average [29]. Biologically compromised individuals tend to be the ones that emigrate from Black Lake [29].…”