Forecasting the Impacts of Climate Change in the Columbia River Basin—Implications for Fish Habitat Connectivity
In the Methow River Basin (MRB), an arid east-central part of Washington State, the USGS and partners have been examining climate change effects on the connectivity of fish habitats and the resultant effects on populations of fish listed under the Endangered Species Act (ESA). In a project with the Bureau of Reclamation, the USGS is studying the fish response to restoration efforts and constructing a model relating stream habitat with fish population dynamics based on empirical data, which include water temperature and flow, fish distribution and abundance, stream productivity (nutrients, macroinvertebrate production), and measures of lateral and longitudinal connectivity of habitat (e.g., side channels, springs).
Numerous Pacific Northwest species are listed under the ESA, including five iconic Pacific salmon species and several other non-anadromous salmonids such as the bull trout (Salvelinus confluentus) and westslope cutthroat trout (Oncorhynchus clarkii). All of these fish need a variety of habitat types that include appropriate water temperatures, flows, refuge from predators, and adequate food. Key to fish using these resources is the connectivity of habitats in which they are found. This connectivity is seriously threatened by changes in flow and temperature predicted with global climate change.
Great Northern LCC-funded Study Addresses Three Tasks
In 2010, we received funding from the Great Northern LCC to accomplish three tasks using fish growth, distribution and movement, foodweb data, river flow and water temperature to develop spatially-explicit bioenergetics models to assess effects of climate change on the viability of salmonid populations. The bioenergetics models, which predict growth of fish based on fish species and size, diet, activity and water temperature, will integrate such things as climate-driven alterations in the physical environment (water flow, temperature, habitat connectivity), changes in food availability from the perspective of fish as prey and predators, fish movements within the MRB and into the Columbia River, and the growth of individuals.
Migration of large predators (mountain whitefish)
Mountain whitefish (Prosopium williamsoni) are among the most abundant native fishes in western North America, yet their role in ecosystems is largely unknown. Without needed information, mountain whitefish have often been viewed by both the public and fisheries managers as undesirable and perceived as competitors with other more desired game species. We have begun exploring the importance of this species, as a surrogate for other large fish that are ESA-listed, as a competitor or predator of ESA-listed salmon and steelhead in the MRB. This is being accomplished by documenting movement of fish between the MRB and Columbia River (using PIT tag technology and otolith analysis) and sampling their diet.
Diet data will be used to explore what prey items are important in subsidizing these fish in each location and allow us to assess the overlap in resources between mountain whitefish and other salmonids. We are also collecting otoliths (small bones in the ears of all vertebrates) that can be used to determine the annual growth rate of fish by counting rings similar to those on a tree. We can also determine where the fish was when it grew by the chemical composition of the otoliths, which will be the same as the water in which the fish fed.
Bioenergetics of fish
Bioenergetics models are useful tools for fisheries management and researchers because they can predict consumption, growth, and production of fish relative to things such as water temperature, diet, and fish size. During the past year, we completed the bioenergetics model for bull trout (Mesa, M.G., L.K. Weiland, H.E. Christiansen, S.T. Sauter and D.A. Beauchamp. In review. Development and Evaluation of a Bioenergetics Model for Bull Trout).
To help understand the relationship between predator and prey, along with predicting responses to climate-driven changes in the environment, we are developing a bioenergetics model for mountain whitefish. Data for these models are generated in the laboratory by putting fish in a respirometer where water temperature, diet, and fish size are known and the amount of oxygen used by a fish is a measure of the calories burned (respiration). Calories used in respiration are not available for growth, which is important for survival of the fish.
Modeling habitat connectivity
We are helping develop a 2-D hydrodynamic model of the Methow River between the towns of Winthrop and Twisp by measuring the bathymetry of flood plain areas along the reach. We will identify habitat criteria for each fish species, by life-stage, in the MRB, develop spatially explicit models and maps of salmonid habitat, create habitat-discharge response curves, identify habitat amount and connectivity between side-channel and main-stem reaches across a range of flows, and quantify effects of climate change on salmonid habitats and connectivity. Tasks will require defining, quantifying, and identifying salmonid habitats with a hydrograph produced under baseline climatic conditions (e.g., 1980–2009) and then altering the hydrograph to simulate future climatic conditions (e.g., 2010–2039, 2040–2069, 2070–2099), thus resulting in a new set of habitat maps.
Perhaps the most important element of our ongoing project will be a workshop involving many of the fish biologists working in the MRB. The goal of this workshop will be to ensure that all of our work is reasonable and connects with the research being conducted by other Federal, State, Tribal and non-governmental agencies. The workshop is not yet not scheduled.