Threatened Chinook Salmon Populations

Change in Stream Levels and  effects on Salmon Spawning

Changes in temperature and precipitation will continue to decrease snow pack, and will affect stream flow and water quality throughout the Pacific Northwest region. Warmer temperatures will result in more winter precipitation falling as rain rather than snow throughout much of the Pacific Northwest, particularly in mid-elevation basins where average winter temperatures are near freezing. This change will result in less winter snowfall and more winter precipitation. Coupled with rising winter temperatures, diminished snow pack levels will have earlier melting times, altering seasonal stream levels. Change in peak spring flow by as little as 3 weeks will have a profound effect on salmon, whom rely on rivers and streams to complete their lifecycle.

Increased carbon and green house gas emissions is changing the earth's climate, leading to warmer winter temperatures, decreased winter snowfall, and increased winter precipitation levels. Warmer temperatures are causing already decreased snowpack to melt earlier in season leading to earlier and more intense winter peak stream flow and decreased spring peak stream flow. This change in timing leads to Predator-prey decoupling between plankton blooms and salmon as well as  challenging salmon's ability to reach freshwater habitat for spawning. Warmer stream temperatures negatively affect the quality of salmon's habitat and stronger stream flows can force juvenile Salmon into estuaries before they reach maturity.    Figure credit: Katie Heckel

 

The US Forest Services describes the potential effects of climate change on this PNW species:

" Many effects of climate warming, however, will have negative habitat consequences for salmon. A higher frequency of severe floods will result in increased egg and alevin mortality owing to gravel scour, especially for fall- and winter-spawning species. Retreating winter snowpacks will run off earlier in the spring (Mote et al. 2003), potentially altering the life cycles of salmon whose seaward migration is timed to coincide with nearshore plankton blooms (Pearcy 1997). Summer base flows will be lower, and the network of perennially flowing streams in a drainage system will shrink during the summer dry period, forcing fish into smaller wetted channels and less diverse habitats (Battin et al. 2006). Warmer water temperatures will increase physiological rearing costs and lower growth rates if warmer streams do not produce sufficient food resources to offset heightened metabolic demands. Additionally, summer temperatures may approach or exceed incipient lethal levels for salmon and trout (Crozier et al., 2008), and higher temperatures will likely favor non-salmonid species that are better adapted to warmer water, including potential predators and competitors (Reeves et al. 1987)."
(US Forest Service, 2012)

Climate Change and the effects on Salmon Lifecycle

Climate predictions indicate warmer summer temperatures and changing hydrological regimes in the future of the Pacific Northwest. Predicted conditions will lower the chances of survival for juvenile salmon as well as influence the migratory behavior and fertility of adult salmon. Trends show increasing temperatures in the Salmon River basin exceeding tolerable levels for salmons (13 degrees Celsius). The lifecycle and therefore survival of this species will be greatly impacted by increasing winter and spring temperatures and it's affects on snow pack melt, timing and magnitude of stream levels, and how rising summer temperatures will lead to warmer streams.
(Crozier et. al, 2006)

Predicted Changes in PNW climate:

globachange.gov

Rising stream temperatures will reduce the quality of freshwater habitat and extend beyond the favorable temperature for Salmon. The effects of warmer streams and warmer temperatures combined with alterations in stream flow from earlier peak snow melt will most likely negatively effect reproductive success of Washington salmon populations.

http://www.fws.gov/pacific/Climatechange/changepnw.html

"As more winter precipitation falls as rain rather than snow, higher winter stream flows scour streambeds, damaging spawning nests and washing away incubating eggs for Pacific Northwest salmon.  Earlier peak stream flows flush young salmon from rivers to estuaries before they are physically mature enough for transition, increasing a variety of stressors including the risk of being eaten by predators."
(fws.gov, 2012)

 

 Future Conservation Efforts for a PNW keystone species:

Visit the Conservation Efforts: Preserving the Lake Washington/Cedar River Watershed tab for more information on how you can get involved in helping to protect the habitat of this important ecosystem member!

Targeting areas for conservation and viability of this species and therefore it's habitat is complex as with most conservation efforts.

"Ecologists have long recognized the importance of maintaining diverse habitats and multiple independent populations, but the added threats from climate change make this goal even more imperative. Managers can sometimes influence stream flow and temperature, for example, by reducing water diversions or encouraging riparian cover, so identifying the most important environmental forcing factors for a particular population can have conservation benefits." (Crozier et al, 2006)

However, understanding the specific mechanism for survival is necessary for the survival and stabilization of this species. Salmon are considered ‘keystone’ species because "they transfer marine nutrients to otherwise nutrient-poor environments, and provide a crucial food resource for many vertebrates (Willson & Halupka 1995)." Therefore their demise effects the community and ecosystem on a grander scale. It is clear that climate change poses a direct threat to Salmon as well as other species in their community or ecosystem. (Crozier et. al, 2006)