Threats to Wild Pacific Salmon

Winslow C. Johnson


Summary of Salmon Life Cycle and Threats to Wild Populations

U.S. Fish and Wildlife Service: Wildlife Species Information (ACCESSED 4-18-2007)

Threats to Salmon: The Four H’s

Oregon State University Extension Service:

Costs of Restoring Wild Salmon Runs

Blaine Harden, “Salmon or power? In Pacific Northwest, pressure is building.” The Seattle Times: 03-07-2004 (ACCESSED 4-19-2007)


Summary of In-Class Discussion

Talked about aspects of the salmon life cycle that make it particularly susceptible to human impacts.

  • They only breed once in their lives
  • They have a large habitat (tributary, river, coast, ocean) which is affected by the entire watershed.
  • They require well-oxygenated water, being one of the first species of fish to show ill-effects from pollution.
  • Their physiological changes on downstream require a very specific time line.
  • As a given population always returns to the same stream, it is difficult to re-establish extinct populations

Summarized the threats facing wild salmon populations (The Four H’s):

  • Hydroelectric Dams - Kill or delay young smolts on their downstream journey, block adult salmon on their upstream journey.
  • over-Harvesting - In the past, fishermen over-fished wild stocks, leading to the current low populations. Also, because only certain runs are considered endangered or threatened, it is difficult to separate threatened fish from not.
  • Hatcheries - Hatchery fish out-compete wild salmon on the journey downstream.
  • Habitat destruction - Cities and towns have taken over thousands of acres of wetlands, the prime spawning habitat for salmon.

Looked at the costs of protecting wild salmon, particularly the costs associated with habitat restoration and summertime spill, where dams forego millions of dollars worth of electricity to allow young salmon to pass more easily through dams.

Asked whether the costs of protecting salmon were worth the benefits: economic, ecological, and to northwest cultural identity.



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