Email to: wmdendy@umd.edu Objective Survey Terms Species Map of Study Area About W. Mark Dendy Research team Reports Links

Russian: Щелкните ЗДЕСЬ для русского языка. Vietnamese: kích ở đây (cho) tiếng Việt nam Spanish

Advisors: Bretton Kent, Ph.D. – University of Maryland, College Park

Ron Coleman, Ph.D. – California State University, Sacramento

INTRODUCTION

For decades, there has been competition between marine mammals and commercial fisheries worldwide.^1,2 Anadromous fishes found in the Sacramento Delta are part of commercial and recreational fisheries from the coastal regions to the breeding habitats far inland. The fishing industry in the delta area is an important economic element for the local population and keeps people coming back to the area year after year for recreation and for commercial fishing. The California sea lion (Zalophus californianus) and Pacific harbor seal (Phoco vitulina richardsi) are known to prey on salmonids in the ocean and bays.³ The population of California Sea lions in the U.S. was estimated at 237,000 for 2006 and is increasing at an annual rate of 5.4 - 6.1% per year.⁴ With the population of these opportunist feeding pinnipeds growing at such a rapid rate, competition with fisheries has increased.

The anadromous fish populations which migrate inland throughout the Sacramento Delta have declined dramatically in the past 50 years, due to a combination of factors including habitat destruction and overfishing.^5,6 These populations include the Winter run and Spring run Chinook salmon (Oncorhynchus tshawytscha), listed as federal and state threatened,^7,8 steelhead (Oncorhynchus mykiss), federal threatened,⁸ striped bass (Morone saxatilis), white sturgeon (Acipenser transmontanus), and green sturgeon (Acipenser medirostris). California sea lions and Pacific harbor seals have been protected by the federal Marine Mammal Protection Act since 1972.⁹ Although some marine mammals, such as the Hawaiian Monk seal and the Stellar sea lion, remain endangered,¹⁰ the California sea lion and Pacific harbor seal have experienced a population explosion resulting in increased competition for foraging. As sea lions and harbor seals move up into the river system where their natural predators, the killer whales (Orcinus orca) and great white sharks (Carcharodon carcharias)¹¹, are not present, they find themselves at the top of the food web. Therefore, their main competition for resources is humans, particularly recreational fishermen.

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REFERENCES

1. Northridge, S.P. An updated world review of interactions between marine mammals and fisheries. FAO Fisheries Technical Paper. No. 251, Suppl. 1. Rome,

FAO. 1991. 58p.

2. DeMaster, Douglas P., Fowler, Charles W., Perry, Simona L. and Richlen, Michael F. Predation and Competition: The Impact of Fisheries on Marine-Mammal

Populations over the Next One Hundred Years. Journal of Mammalogy, Vol. 82, No. 3 (Aug., 2001), pp. 641-651.

3. National Marine Fisheries Service (NMFS). 1997. Investigation of Scientific Information on the Impacts of California Sea Lions and Pacific Harbor Seals on

Salmonids and on the Coastal Ecosystems of Washington, Oregon, and California. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-NWFSC-28, 172 p.

4. Carretta, James V., Forney, Karin A., Muto, Marcia M., Barlow, Jay, Baker, Jaon, Hanson, Brad, and Lowry, Mark S. US Pacific marine mammal stock

assessments: 2006. U.S. Dept. Commerce., NOAA Tech. Memo NOAA-TM-NMFS-SWFSC-398, (January 2007) 312 p.

5. Draft EIR for the Chevron U.S.A. Long Wharf Marine Oil Terminal (February 27, 2006), section 4. www.slc.ca.gov/Division_pages/DEPM/DEPM_Programs_and_Reports/Chevron%20Long%20Wharf/Word/11%20Sec%204.3.doc.

6. California Marine Life Protection Act InitiativeRegional Profile of the North Central Coast Study Region (May 7, 2007), http://www.dfg.ca.gov/mrd/mlpa/pdfs/nccrp/profile.pdf.

7. Airamé, S., S. Gaines, and C. Caldow. 2003. Ecological Linkages: Marine and estuarine ecosystems of central and northern California. NOAA, National Ocean Service. Silver Spring, MD. (available at: http://biogeo.nos.noaa.gov/products/canms_cd/data/pdfs/ELR.pdf).

8. CDFG, 2001. California's Living Marine Resources: A Status Report (ANR Publication #SG01-11) California Department of Fish and Game, http://anrcatalog.ucdavis.edu.

9. Ficke, Ashley A., Myrick, Christopher A. The Potential Effects of Anthropogenic Climate Change on Freshwater Fisheries (August 2004). Department of Fishery & Wildlife Biology, Colorado State University.

10. Sacramento Valley Workshop, California Legacy Project: Spotlight on Conservation (April 8-9, 2003), Workshop in Chico, http://www.legacy.ca.gov/pub_docs//Sac_Valley_Wkshp_interim_report.pdf.

11. Hester, M., Allen, S., Adams, D., And Nevins. Pinniped Long Term Monitoring Program (Draft) National Park Service. July 2004.

http://oikonos.org/papers/Hester_etal_DraftPRNS.pdf

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