LTREB: Climatic and Density-dependent Effects on the Ecology of Sockeye Salmon and their Freshwater Ecosystems

University Of Washington, Seattle WA

Investigators

Abstract

0128902 Quinn Despite the general appreciation for climatic effects on ecological dynamics, most biological studies are too brief to test for interactions between climatic and biological processes. Alternatively, many long-term studies do not span enough levels of biological organization to provide meaningful insights into the complexity of ecological responses to environmental change. In the last century, population dynamics of anadromous Pacific salmon have been influenced by interactions among large-scale shifts in regional climate, inherent density-dependent regulation, and fisheries activities. We propose to take advantage of unique, highly detailed biological and physical time series that extend for 40-50 years to test for interactions between climatic and biological processes in the freshwater ecosystems used as nursery habitats by sockeye salmon in southwestern Alaska. Sockeye are not only an important fishery resource to commercial and subsistence communities in this region, but are also keystone species, driving many components of freshwater and riparian ecosystems. We have established a series of working hypotheses to investigate interactions among climatic variables (e.g., hydrology, ice-out date) and biological variables (e.g., bear predation, juvenile competition) that interact to control life history evolution and the ecology of sockeye in freshwater ecosystems. Our main research themes are to explore: 1) interactions among habitat features, climate-driven variation in hydrology, bear predation and salmon density controlling the life history patterns and productivity of adult sockeye, 2) sockeye population dynamics and climate as controllers of limnological conditions in lakes used as nursery habitats, and 3) biological and climatic factors controlling growth rates and age at seaward migration in juvenile sockeye salmon. Sockeye are an ideal species for such studies because they occupy stream, lake and open ocean habitats at discrete life history stages, exert top-down control on zooplankton communities, provide important marine-derived nutrients to freshwater ecosystems when they die and decompose, and occur in large, well-studied populations. This LTREB research will: 1) maintain sampling programs to build on existing data sets established over four decades ago in two lake systems of Bristol Bay, Southwest Alaska, 2) continue to develop a state-of-the-art data archive system to ensure long-term data security, and 3) initiate new and retrospective studies to test several hypotheses central to understanding the interactions between climate and the ecology of sockeye and their ecosystems. A major objective is to develop a living database available to investigators from all avenues of freshwater ecology and fisheries biology. These data sets include the abundance, size- and age-structure of adult sockeye salmon, regional climate, limnological conditions in nursery lakes, and abundance and growth of juvenile sockeye salmon and other lacustrine fishes. More specifically, we will evaluate the consequences of climate change for life history evolution and population dynamics of a fish species that plays an exceptionally important role in the structure and function of its ecosystems, and the local economy and culture of people in the region.