Lake trout growth is sensitive to spring temperature in southwest Alaska lakes

In high-latitude lakes, air temperature is an important driver of ice cover thickness and duration, which in turn influence water temperature and primary production supporting lake consumers and predators. In lieu of multidecadal observational records necessary to assess the response of lakes to long-term warming, we used otolith-based growth records from a long-lived resident lake fish, lake trout (Salvelinus namaycush),as a proxy for production. Lake trout were collected from seven deep, oligotrophic lakes in Lake Clark National Park and Preserve on in southwest Alaska that varied in the presence of marine-derived nutrients (MDN) from anadromous sockeye salmon (Oncorhynchus nerka). Linear mixed-effects models were used to partition variation in lake trout growth by age and calendar-year and model comparisons tested for a mean increase in lake trout growth with sockeye salmon presence. Year effects from the best mixed-effects model were subsequently compared to indices of temperature, lake ice, and regional indices of sockeye salmon escapement. A strong positive correlation between annual lake trout growth and temperature suggested that warmer springs, earlier lake ice break-up, and a longer ice-free growing season increase lake trout growth via previously identified bottom-up increases in production with warming. Accounting for differences in the presence or annual escapement of sockeye salmon with available data did not improve model fit. Collectively with other studies, the results suggest that productivity of subarctic lakes has benefitted from warming spring temperatures and that temperature can synchronise otolith growth across lakes with and without sockeye salmon MDN.