Salmon Research and Climate Change

A male coho salmon from the Russian River Coho Salmon Captive Broodstock Program.

Photo Credit: NOAA

By Tom Hom, John Stein, and John W. Ferguson

Concern about the expected impacts of long-term climate changes on natural climate variability is increasing. Ecosystems respond to, and are highly coupled with, climate variability. The effects are particularly acute in the Pacific Northwest, where ocean productivity, snow pack, and river hydrology respond quickly to changes in climate. This region supports a wide diversity of wildlife, including many valuable commercial and recreational fisheries, as well as endangered and threatened salmon populations.

In the Pacific Northwest, the effects of climate change will probably alter the timing of stream flows, reduce summer flows, increase stream temperatures, raise sea level, and change shorelines and ocean current patterns. Concurrently, human population growth in the Northwest will lead to increased demand in coastal communities for fresh water and erosion protection, which could cause additional changes in freshwater, terrestrial, and coastal ecosystems. A critical challenge for the National Marine Fisheries Service (NMFS) and other parts of the National Oceanic and Atmospheric Administration (NOAA) is to increase our understanding of how climate affects ecosystems that support salmon and to develop long-term strategies for maintaining ecological health.

In our watersheds, the effects of climate can alter rainfall patterns, thus increasing the risk of floods and reducing snowpack, which lowers summer stream flows. In the coastal ocean, climate affects the key process of coastal upwelling, a process that brings deep, nutrient-rich waters to the surface and fuels the growth of phytoplankton, which forms the base of the marine food web. Changes in this upwelling can propagate through the food web to such species as salmon by affecting the survival of juvenile fish when they swim from their natal stream into the ocean. Changes in marine water temperature can also affect salmon survival by influencing the distribution and abundance of predators. Thus, to conserve Pacific salmon, it is important to investigate climate effects from the “snowcaps to white caps” and provide scientific advice for mitigating and adapting to climate change.

Chinook salmon.

Photo Credit: NOAA

For Pacific salmon, NMFS research priorities are to identify sensitive and resilient ecosystems and communities, then characterize the likely ecological effects of predicted changes in climate. The findings will provide NMFS, states, tribes, and local governments with a sound scientific basis for developing longterm management responses to climate change.

Climate-related Salmon Research

Climate-related research for the conservation of Pacific salmon takes place at NMFS’ Northwest Fisheries Science Center (NWFSC) in Seattle, Washington. Scientists at the NWFSC are: 1) investigating how to predict changes in watershed processes (including, but not limited to, stream flows) at local-tobasin scales, 2) identifying physical and ecological characteristics that indicate the status of freshwater and coastal marine ecosystems, 3) combining field observations with models to predict the future response of salmon and other species to climate change, and 4) identifying and developing recovery strategies for listed salmon populations. Geographically, our research extends from headwater streams through the watershed to the estuary and into the ocean, and biologically from the base of the food web to top predators, such as killer whales. Some highlights of current research follow:

Ocean and Climate

Climate fluctuations can alter oceanic processes that affect the growth, survival, and abundance of marine and anadromous fish (species that become sexually mature in the ocean and migrate to freshwater rivers to spawn), along with their predators and prey. For example, changing water temperature influences the distribution and abundance of predators, and climate overall affects patterns of larval dispersal, growth and settlement, and survival to adulthood of prey species.

The NWFSC conducts ecological research to predict how human activities and management decisions may affect species abundance and status. This includes investigations of ocean habitats that juvenile salmon prefer; climatedriven physical forces that affect ocean conditions, plankton production, and fish community structure; and the interactions among freshwater, estuarine, and ocean ecosystems that affect salmon recruitment. The NWFSC maintains an online database on changing ocean conditions in the northern California Current (see www.nwfsc.noaa.gov) that provides information about key ecosystem indicators that forecast adult salmon returns. Other research topics include the effects of climate on salmon feeding and bioenergetics (in this case, increased food requirements for juvenile salmon in warmer waters) and the potential impacts of climate on salmon predators, such as killer whales (Orcinus orca). The southern resident killer whale, the term given to a group that visits the Puget Sound every summer, was listed in 2005 as endangered.

Sockeye salmon.

Photo Credit: NOAA

Estuary and Climate

In the Columbia River estuary, NWFSC scientists are investigating how juvenile salmon use a variety of habitats, which habitats are most important for their survival, and how the timing of juveniles moving through the estuary into the ocean is affected by river flow and ocean conditions, both of which are influenced by climate variability. In the Puget Sound, an integrated assessment is underway to identify ecosystem indicators, assess risks to key ecosystem components, and evaluate management strategies to maintain and restore ecosystem processes and productivity in the face of climate change. In addition, we are modeling climate, hydrology, and salmon population dynamics to support salmon recovery efforts.

Freshwater and Climate

Freshwater ecosystems are critical for salmon and other anadromous fishes. Climate directly affects the hydrologic cycle and stream temperatures, which can affect spawning, migration timing, and juvenile survival. Models have been developed to estimate the impact of flood strength on survival of salmon eggs and fry (newly hatched salmon), and there are ongoing studies on migration behavior in response to changing river conditions. An example of the latter is a study on the migration timing and survival of wild Snake River juvenile spring/summer Chinook salmon (Oncorhynchus tshawytscha) in response to changes in river flow and elevated water temperature. Research is also underway on whether, and how, restoration strategies could mitigate the effects of climate change and aid salmon recovery. In examining restoration strategies, models of climate, land cover, and hydrology are linked with the salmon population biology to identify the best strategies for salmon conservation in the face of climate change.

Tom Hom is the leader of the NWFSC’s Outreach and Science Communication Team (tom.hom@noaa.gov, 206-860-3337), Dr. John E. Stein is the Deputy Science and Research Director of the NWFSC (john.e.stein@noaa.gov, 206-860-3438), and Dr. John W. Ferguson is the Director of the Fish Ecology Division at the NWFSC (john.w.ferguson@noaa.gov, 206-860-3270).