Fish and Wildlife

Given the variety of fish and wildlife species in Oregon, the effects of climate change on them could be far-reaching. Below is an example of how climate change may impact native salmon.

Concerns have been clearly voiced about the effects of climate change on the distribution and fitness of native salmon in the Pacific Northwest. A great deal of discussion dedicated to monitoring and predicting climate change effects on salmon populations in this region has occurred, with analysis of how various factors such as temperature, flow, sedimentation and snowpack will impact fish at each stage of their life cycle (e.g. Bratten et al. 2007; Farrell et al. 2008; Yates et al. 2008). However, the implications of climate change for altered disease effects are rarely considered despite the role that pathogens play in regulating these host populations (Marcogliese 2001). Disease transmission and development may be critical factors at increased temperatures (Rand et al. 2006), and for salmon, temperatures above the threshold of 17-18˚C increase loss associated with disease and parasites (Farrell et al. 2008).

Epizootics in salmon as a result of viral, bacterial, fungal and parasitic pathogens have been documented under conditions of increased temperature (Doppelt et al. 2009, Traxler and Rankin 1989). Examples include the 2002 adult fish kill in the Klamath River (Guillen 2003) and similar circumstances in 2004 where fish perished in the Fraser River as a result of disease during periods of high temperature (Rand et al. 2006).  More important for long-term effects on salmon are parasites that cause chronic loss of juvenile fish. In the Klamath River, the primary pathogen for outmigrant smolts is Ceratomyxa shasta (Nichols et al. 2009). This myxozoan is endemic in most large rivers in the Pacific Northwest and infects all species of Pacific salmon.  The C. shasta life cycle is complex and involves the polychaete Manayunkia speciosa (Bartholomew et al. 1997), with myxospore stages of the parasite released from the fish infecting the polychaete, and actinospore stages released from the polychaete infecting the fish.

It is clear that the consequences of climate change on host:pathogen interactions are numerous and for salmonids include: 1) altered impacts of pathogens as their virulence and/or densities increase and as the fitness of salmon is challenged by increasing temperatures; 2) changes in seasonal disease cycles with milder winter temperatures; and 3) altered distribution of pathogens as cold-temperature constraints are reduced. Added to this is the altered effectiveness of management strategies as the amount of cold, fresh water becomes limited. These changes will be seen not only in the microcosm of the Klamath River, but will occur throughout the Pacific Northwest. The challenge will be to predict changes in disease in response to climate so that we can understand and mitigate the effects on wild populations and aquaculture programs that rely on surface water.


Battin, J. M. Wiley, W., Ruckelshaus, M. H., Palmer, R. N., Korb, E., Bartz, K. K. and Imaki, H. (2007) Projected impacts of climate change on salmon habitat restoration. Proceedings of the National Academy of Sciences 104: 6720-6725.

Farrell, A. P., Hinch, S. G., Cooke, S. J., Patterson, D. A., Crossin, G. T., Lapointe, M. and Mathes, M. T. (2008) Pacific salmon in hot water: applying aerobic scope models and biotelemetry to predict the success of spawning migrations. Physiological and Biochemical Zoology 81:697-708.

Yates, D., Galbraith, H., Purkey, D., Huber-Lee, A., West, J., Herrod-Julius, S. and Joyce, B. 2008. Climate warming, water storage, and Chinook salmon in California’s Sacramento Valley. Climate Change 91:335-350.

Marcogliese, D.J. (2001) Implications of climate change for parasitism of animals in the aquatic environment. Canadian Journal of Zoology 79: 1331–1352.