Difference between revisions of "Coho Salmon Crisis in the Central California Coast ESU"

Revision as of 13:35, 2 February 2010

A watershed-related issue examined by the ENVS 560/L Watershed Systems class at CSUMB.

Summary

Current Issue

Marin County's Lagunitas Creek Watershed, once held out as a statewide model for fisheries restoration, is now hanging in the balance with an unprecedented 90% decline in coho salmon returning to spawn so far this year^[1]. Fisheries and watershed biologists say that several years of exceptionally reduced winter rainfall have contributed to the worst coho salmon return in recorded history. The decreased rainfall translates as reduced creek flow which prevents salmon from effectively swimming upstream and being more vulnerable to predation in the open ocean.

History^[2]

Lagunitas Creek Watershed offers unique spawning grounds in that it is in the midst of a developed area. While historic Coho salmon runs numbered in the thousands a hundred years ago, subsequent redwood logging operations followed by road and housing construction reduced the original salmon habitat to 40% of its original size. The 7 dams spread throughout the area also significantly blocked off historic salmon habitat while also reducing gravel needed for spawning while also increasing creek sediment. In the early 1980s, restoration efforts started with the lobbying of a Trout Unlimited to the county make efforts to halt the salmon fishery decline.

Significance

This unprecedented decline is particularly troublesome because the Lagunitas Creek Watershed is considered one of California's most critical ecosystems for endangered coho salmon^[3]. Historically the Lagunitas Creek Watershed has supported California's largest wild salmon run, regularly supporting 10% of the state's Coho Salmon population^[4]. The Lagunitas Creek watershed salmon population is also considered considered critical for the coho salmon population of the entire central California coast ^[2]. Salmon have been regularly taken from this watershed to supplement populations in regional watersheds There are now probably less than 5,000 native coho salmon (with no known hatchery ancestry) spawning in California each year, many of them in populations of less than 100 individuals. Coho populations today are probably less than 6% of what they were in the 1940s, and there has been at least a 70% decline since the 1960s. There is every reason to believe that California coho populations, including hatchery stocks, will continue to decline, The reasons for the decline of coho salmon in California include: stream alterations brought about by poor land-use practices (especially those related to logging and urbanization) and by the effects of periodic floods and drought, the breakdown of genetic integrity of native stocks, introduced diseases, over harvest, and climatic change. This local scale salmon decline is consistent with the recent plummeting of statewide salmon populations that prompted the chinook salmon fishery collapse and subsequent closure along the west coast.

Reason for Decline

Location

Lagunitas Creek Watershed winds through San Geronimo Valley on the northwest side of Mount Tamalpaisis in Marin County, California^[5]. The Lagunitas Creek Watershed coho salmon are part of the Central California Coast Evolutionarily Significant Unit (ESU) that extends from Punta Gorda in northern California south to and including the San Lorenzo River in central California^[6]. This ESU status was designated 1999^[3].

Resource/s at stake

Fishery biologists fear that the severe decline in returning Coho Salmon may result in a spawning failure and possible extinction for the year. Biologically speaking, diminished population size can negatively effect the genetic diversity of the population and reduce fitness or viability for the future. Genetic diversity is a significant concern with with most native spawning coho salmon populations consisting of less than 100 individuals^[1]. Economically, reduced salmon numbers can negatively impact human communities that have relied on salmon fishing for income and tourism.

Stakeholders

• SPAWN (Salmon Protection and Watershed Network)
  • Created in 1996, sponsors salmon-watching creek walks during spawning season and has saved more than 15,000 salmonids from diminishing summer pools.
• Trout Unlimited
  • Trout Unlimited- lobbyists
• The Marin Municipal Water District
  • Required by the state to help the coho as mitigation for raising Peter's Dam, started counting coho redds in the early 1990s and now works with SPAWN to monitor releases from the dam, install woody debris in the creeks and replant vegetation.
• National Marine Fisheries biologists
  • What do the biologists do? Study salmon populations
• National Oceanic and Atmospheric Administration (NOAA)
  • Studying and monitoring endangered species
• Area Residents
  • Community members and schools organize work parties and teach children about the historic coho migration
• Regional Fishers & Fish-related industry
  • Many communities depend on the fish as a source of income

Laws, policies, & regulations

• In 2005 Coho salmon were listed as endangered under the United States Federal Endangered Species Act^[7]

Systems

• Climate change may be contributing to warmer and drier winters with less rainfall. The resulting creek flow limits salmon ability to navigate to the spawning grounds.
• The salmon form part of the food web that with their disappearance may become deranged
• The Coho salmon habitat and watershed integrity were negatively impacted by logging and development which reduced available habitat, stream connectivity and flow^[2]. The resulting decreased creek gravel and increased sediment contribute to reducing critical spawning habitatCite error: Closing </ref> missing for <ref> tag

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