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West Coast Pinniped Program Investigations on California Sea Lion and Pacific Harbor Seal Impacts on Salmonids and Other Fishery Resources

January 01, 2010

Pacific States Marine Fisheries Commission. Joe Scordino (Retired - NOAA/National Marine Fisheries Service - Northwest Region).

This report provides the results of the West Coast Pinniped Program established in 1997 by NOAA Fisheries and the Pacific States Marine Fisheries Commission to investigate the impacts of expanding pinniped populations on salmonids, especially ESA-listed salmon, and other fishery resources. The Program was primarily funded with Congressionally designated line-item funding of about $750,000 per year for “a study of the impacts of California sea lions and harbor seals on salmonids and the West Coast ecosystem.” Over 150 projects were completed through 2008 and are described in this report. The accomplishments of the West Coast Pinniped Program relative to the recommendations in the 1999 “Report to Congress: Impacts of California Sea Lions and Pacific Harbor Seals on Salmonids and West Coast Ecosystems” is presented in the conclusion.

Investigations on pinniped predation on salmonids were conducted in west coast rivers and estuaries including rivers draining into Hood Canal, Ozette River, Columbia River, Alsea River, Rogue River, Klamath River, Mad River, and San Lorenzo River; and at Bonneville Dam, Willamette Falls, San Juan Islands, Año Nuevo Island, and Monterey Bay. The field studies used observations of pinniped surface-feeding events to estimate salmonid predation and/or analyses of pinniped fecal material (scat) to determine overall diet, as well as tracking of pinniped movements to infer foraging behavior. Captive feeding studies were conducted to assess prey digestion variables that affect pinniped consumption estimates derived from scats. Genetic identification techniques were developed and applied to identify salmonid species from the bones in scats. The pinniped predation studies documented that salmonids are a common prey species for Pacific harbor seals and California sea lions in many west coast rivers/estuaries and even in open marine waters (e.g., Monterey Bay), and pinnipeds can adversely affect the recovery of ESA-listed salmonid populations.

The population growth and status of California sea lion and Pacific harbor seal populations were investigated, and assessments indicated the Washington and Oregon harbor seal populations were at their optimum sustainable population (OSP) levels. Population assessments initially demonstrated that California sea lions had reached OSP, but continued exponential growth indicated from the 2006 to 2008 pup counts suggest the population is not yet at OSP. Additional surveys are needed to affirm California harbor seal status.

 Pinniped interactions with commercial and recreational fisheries in California were investigated. California sea lions were documented interacting with hook-and-line fisheries for salmon, Pacific barracuda, yellowtail, and other important fishery species. The removal of catch or bait from fishing gear was the principal interaction problem; the severity of loss varied by area, target species, and year.

Pinniped deterrence efforts to deter or remove pinnipeds from resource conflicts including hazing, pyrotechnics, acoustic deterrence, underwater shock waves (pulsed power), taste aversion, rubber projectiles, electric barriers, and physical barriers are described and evaluated. The evaluation indicated that the non-lethal deterrence measures have limited effectiveness; while some measures appeared to be initially effective, they became ineffective over time as pinnipeds “learned” to either tolerate or avoid the deterrence measure.

The West Coast Pinniped Program made significant progress in developing and applying methodologies to determine pinniped impacts on salmonids; however, further research is needed to better estimate pinniped impacts on ESA-listed salmonids.

Last updated by West Coast Regional Office on 09/23/2019