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

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(Reason for DeclineBrown, L.R., Moyle, P.B. 1991. Historical Decline and Current Status of Coho Salmon in California. North American Journal of Fisheries Management http://www.russianriverwatershed.net/docManager/1000000622/brown1991.pdf)
(Reason for DeclineBrown, L.R., Moyle, P.B. 1991. Historical Decline and Current Status of Coho Salmon in California. North American Journal of Fisheries Management http://www.russianriverwatershed.net/docManager/1000000622/brown1991.pdf)
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=== Reason for Decline<ref name="Status">Brown, L.R., Moyle, P.B. 1991. Historical Decline and Current Status of Coho Salmon in California. North American Journal of Fisheries Management http://www.russianriverwatershed.net/docManager/1000000622/brown1991.pdf</ref> ===
 
=== Reason for Decline<ref name="Status">Brown, L.R., Moyle, P.B. 1991. Historical Decline and Current Status of Coho Salmon in California. North American Journal of Fisheries Management http://www.russianriverwatershed.net/docManager/1000000622/brown1991.pdf</ref> ===
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The primary reason for the decline of coho salmon in Lagunitas Creek appears to be due to the construction of the Kent and Nicasio Reservoirs, which restricted the fish to the lowermost portion of the creek.
  
 
Lagunitas Creek is a tributary to Tomales Bay and empties into the southern part of the bay.
 
Lagunitas Creek also known as Papermill Creek, produced a state record coho salmon in 1959
 
(Giddings 1959). Presently the population appears to be very low. The primary reason for the decline
 
appears to be the construction of Kent and Nicasio Reservoirs, which restricted anadromous fishes to
 
the lowermost portions of Nicasio and Lagunitas Creek. When Nicasio Reservoir was first constructed
 
adults were trapped below the dam and transported above the reservoir where they were allowed to
 
spawn naturally. Outmigrant juveniles were trapped in Nicasio and Halleck Creeks and transported
 
below the dam. These programs began in 1961 upon completion of the project (Quinn and Alan
 
1969a). During the 1962-1963 season 44 adult coho salmon were released above the reservoir and in
 
1963-1964, 151 adult coho salmon were released above the reservoir (Quinn and Alan 1969a). Six
 
hundred twenty adult coho salmon were captured in the 1964-1965 season (Quinn and Alan 1969b).
 
No juvenile downstream migrant coho salmon were capture in 1961 or 1962. No data are available for
 
1963. In 1964, 943 coho salmon juveniles were captured and in 1965, 41,697 were captured. This
 
extremely large number was the result of a plant of hatchery-reared coho salmon during the previous
 
winter. The ratio of hatchery yearlings to natural yearlings was roughly 260 to 1. Large numbers of
 
naturally produced young of year also migrated, suggesting that space may have been limiting. This
 
program was eventually discontinued (L. Cronin, pers. comm.).
 
A redd count conducted in 1991 indicated only 20 pairs of coho salmon spawning in the stream
 
(L. Cronin, pers. comm.). Flows were so low that coho never reached a trapping site where eggs have
 
been taken in previous years for enhancement of natural reproduction and to maintain the natural gene
 
pool in the event of scouring flows. The success of the limited spawning in 1991 may be in jeopardy
 
because of superimposition of steelhead redds. Steelhead entered the stream in March 1991 and
 
spawned in the same areas used by the coho salmon (L. Cronin, pers. comm.).
 
Emig (1985) recommended planting of riparian vegetation, erosion control measures and
 
32
 
additional stockings of 100,000 coho smolts for 3 years to restore the depleted coho population. He
 
also recommended using native eggs. At the time, 40,000 smolts were stocked annually as mitigation
 
for the Nicasio project. He also suggested that regulations prohibiting fishing should continue.
 
 
Lack of appropriate spawning gravel is one of the problems affecting coho salmon in this creek.
 
Lack of appropriate spawning gravel is one of the problems affecting coho salmon in this creek.
 
Construction of the reservoirs has prevented recruitment of new gravel into most of the system resulting
 
Construction of the reservoirs has prevented recruitment of new gravel into most of the system resulting
 
in a streambed dominated by relatively large and angular particles. Most spawning now takes place in
 
in a streambed dominated by relatively large and angular particles. Most spawning now takes place in
 
San Geronimo Creek, an unregulated tributary, and the region immediately downstream of its
 
San Geronimo Creek, an unregulated tributary, and the region immediately downstream of its
confluence with Lagunitas Creek (L. Cronin, pers. comm.). Though no numbers are available, the
+
confluence with Lagunitas Creek.
present population appears to be only a small remnant of the population in the early 1900s when special
+
trains brought anglers from the Bay area to fish for adult coho salmon and steelhead (Smith 1986).
+
  
 
== Location ==
 
== Location ==

Revision as of 19:03, 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[5]

The primary reason for the decline of coho salmon in Lagunitas Creek appears to be due to the construction of the Kent and Nicasio Reservoirs, which restricted the fish to the lowermost portion of the creek.

Lack of appropriate spawning gravel is one of the problems affecting coho salmon in this creek. Construction of the reservoirs has prevented recruitment of new gravel into most of the system resulting in a streambed dominated by relatively large and angular particles. Most spawning now takes place in San Geronimo Creek, an unregulated tributary, and the region immediately downstream of its confluence with Lagunitas Creek.

Location

Lagunitas Creek Watershed winds through San Geronimo Valley on the northwest side of Mount Tamalpaisis in Marin County, California[6]. 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[7]. 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

Laws, policies, & regulations

  • In 2005 Coho salmon were listed as endangered under the United States Federal Endangered Species Act[8]

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 habitat [5].

Scientific questions

  • Examining whether restoration efforts actually improved the watershed conditions?
  • Examining whether reduced creek water flow is more due to changes in weather patterns alone or a combination of weather patterns in conjunction with development in the watershed reducing its capacity or decreasing flow.

Relevant scientific tools

  • Fish could be tagged and tracked, but that might be difficult considering life span and size.
  • Fish that are assisted out of drying ponds could be monitored for survival rate with GPS tracking information.
  • Weather models could be implemented to predict required rainfall patterns.
  • Genetic tools to investigate genetic diversity of coho salmon population and what percentage is "pure wild type" versus those with stock ancestry.

Future research

  • Given unlimited money the remaining population's genotype could be assessed to deem if there is sufficient diversity remaining for re-population. If so, a breeding program that tracks and pairs individuals could be started to increase genetic diversity. Especially important if this population was used to restock other locations. Also genetic analyses could be done to test whether distinct morphotypes reflect genotype diversity.

Notes and References

  1. 1.0 1.1 Fimrite, P. 2009. Crisis Situation for Marin's coho salmon. San Francisco Chronicle. 01092009 Section B1
  2. 2.0 2.1 2.2 Brown, L.R., Moyle, P.B. & Yoshiyama, R.M. 1994. Historical Decline and Current Status of Coho Salmon in California. North American Journal of Fisheries Management 14.2:237–261
  3. 3.0 3.1 NOAA Fisheries Office of Protected Resources http://www.nmfs.noaa.gov/pr/species/fish/cohosalmon.htm
  4. http://sfbay.sierraclub.org/yodeler/html/2009/09/winter5.htm
  5. 5.0 5.1 Brown, L.R., Moyle, P.B. 1991. Historical Decline and Current Status of Coho Salmon in California. North American Journal of Fisheries Management http://www.russianriverwatershed.net/docManager/1000000622/brown1991.pdf
  6. http://en.wikipedia.org/wiki/Lagunitas_Creek
  7. http://www.nwr.noaa.gov/ESA-Salmon-Listings/Salmon-Populations/Coho/
  8. http://www.nmfs.noaa.gov/pr/laws/esa/

Links

Disclaimer

This page may contain student work completed as part of assigned coursework. It may not be accurate. It does not necessary reflect the opinion or policy of CSUMB, its staff, or students.