Seals and sea lions are part of a healthy Salish Sea and Pacific Coast ecosystem.
Populations of these charismatic animals were severely depleted due to hunting and intentional killing well into the 1960s, when they were at fractions of their historic abundance. Thanks to federal laws like the Marine Mammal Protection Act, many populations of seals and sea lions are recovering all along the West Coast, and returning to areas that they historically occupied. Sadly, with their recovery, seals and sea lions, particularly harbor seals and California sea lions, have once again become the target of those who blame them for “eating too many fish,” and they are falsely charged with the decline of the endangered Southern Resident killer whale population, which is highly dependent on salmon for survival. Ecosystem health and recovery is a complex issue, and killing an important component of a functioning ecosystem will be far more harmful than helpful.
Killing seals and sea lions will not save Southern Resident killer whales (orcas).
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The decline of Southern Resident orcas is complex and has been linked to many factors, including significantly reduced abundance of their preferred prey (Chinook salmon), high levels of contaminants, and increased disturbance from vessels and noise. [1]
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While the decline of Chinook salmon has been recognized as the biggest threat to the orcas’ survival, salmon are also threatened by a complex mix of issues, including habitat degradation, dams and human-made barriers on rivers, pollution, and climate change. For example, in the Columbia Basin alone, dams completely block access to more than 55% of historic Chinook habitat. [2]
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There is no scientific evidence that killing harbor seals, California sea lions, or Steller sea lions would have any benefit to salmon survival. In fact, the best available science indicates the opposite – killing them will likely create a cascade of unintended ecosystem impacts, and may in fact further impede salmon recovery. [3] Because seals and sea lions also consume many fish that are themselves salmon predators, they help keep those predators in check and decrease additional predation on salmon.
Seals and sea lions do not eat large amounts of endangered salmon.
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Sea lions and seals both consume dozens of different species of fish and other marine life. While they do eat salmon, it’s a relatively small percentage of their diet. [4]
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The diet of California sea lions, in particular, includes sardines, anchovies, rockfish, mackerel, and hake (a significant predator of salmon). [5]
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All of the major salmon rivers in the Pacific Northwest and California have salmon runs listed as endangered. The status of individual stocks varies due to many factors, including the extent of habitat loss, access to habitat, fishing pressure, and ocean conditions. [6]
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Salmon populations, endangered or otherwise, fluctuate independently of the size and presence of seal and sea lion populations. [7] There is no direct correlation between “fewer salmon” and “more seals or sea lions.”
Seals and sea lions are part of a natural, healthy Pacific Northwest ecosystem.
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Sea lions have historically been common all along the West Coast. Sea lions and harbor seals have both been documented as far up the Columbia River as what is now Bonneville Dam, and likely as far inland as what was once Celilo Falls. [8]
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Both seals and sea lions in the Salish Sea and along the West Coast represent populations that have recovered from being hunted to numbers in the mere thousands by the middle of the 20th century. [9]
Seals and sea lions are not overpopulating the Pacific Northwest
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Populations of harbor seals grew steadily in the Salish Sea until the mid-1990s, when they appear to have remained relatively stable for the last 25 years. [10]
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The coastwide population of California sea lions has been steadily increasing since the Marine Mammal Protection Act was enacted in 1972. However, notable fluctuations linked to oceanic events such as El Niño and the recent warm-water “Blob” have caused sharp declines, including the loss of 50,000 California sea lions from 2012-2014. [11]
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The Eastern population of Steller sea lions is recognized as a Distinct Population Segment (DPS) and was listed as Threatened under the Endangered Species Act until 2013. As the Western DPS remains listed as Endangered, the Eastern population has become important for the long-term survival of the species. [12]
Seals and sea lions are still in need of protection
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Hundreds of seals and sea lions are killed each year by human-related activities, ranging from the unintended consequences of entanglement in fishing gear and vessel strikes to intentional shootings. [13]
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Federal law recognizes the important role of seals and sea lions in their ecosystems. As mid-level predators, seals and sea lions are an important part of the complex ecosystems of the Salish Sea and the California Current. They are indicator species for environmental concerns, are a vital prey source for Bigg’s (mammal-eating) orcas, and consume fish species that are predators of salmon. [14]
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Non-lethal management measures, such as removing haul-out areas that encourage large congregations of seals and sea lions and altering hatchery management practices that impact salmon survival, should be implemented and assessed before resorting to killing seals and sea lions.
References
[1] National Marine Fisheries Service. 2016. Southern Resident Killer Whale 5-Year Review: Summary and Evaluation. https://www.fisheries.noaa.gov/resource/document/southern-resident-killer-whales-orcinus-orca-5-year-review-summary-and-evaluation
[2] Northwest Power and Conservation Council (n.d.). Dams: impacts on salmon and steelhead. Retrieved from https://www.nwcouncil.org/reports/columbia-river-history/damsimpacts
[3] Bowen and Lidgard. 2012. “Marine mammal culling programs: Review of effects on predator and prey populations.” Mammal Review 43 (3), January 2012. Pp. 207-220; and Morissette L, Christensen V, Pauly D (2012) Marine Mammal Impacts in Exploited Ecosystems: Would Large Scale Culling Benefit Fisheries? PLoS ONE 7(9): e43966. https://doi.org/10.1371/journal.pone.0043966
[4] Majewski, S. et al. "Harbour seals consume more juvenile and adult salmon in estuaries than elsewhere in the Strait of Georgia" (2018). Salish Sea Ecosystem Conference. 453. https://cedar.wwu.edu/ssec/2018ssec/allsessions/453
[5] Lowry, M. 2011. “Photographic Catalog of California Marine Fish Otoliths: Prey of California sea lions (Zalophus californianus).” NOAA Technical Memorandum, NOAA-TM-NMFS-SWFSC-483; Robinson et al. 2018. “Changes in California sea lion diet during a period of substantial climate variability.” Marine Biology, 165:169
[6] NOAA Fisheries. Chinook salmon – protected: https://www.fisheries.noaa.gov/species/chinook-salmon-protected
[7] Tidwell, KS. et al. 2017. “Evaluation of pinniped predation on adult salmonids and other fish in the Bonneville Dam tailrace.” U.S. Army Corps of Engineers, Portland District Fisheries Field Unit. Cascade Locks, OR. 54pp; Bonneville Power Administration. “Millions of Columbia River salmon return home in 2015.” December 1, 2015. Available: https://www.bpa.gov/news/newsroom/Pages/Millions-of-Columbia-River-salmon-return-home-in-2015.aspx; Columbia River Mouth Fish Returns, Fish Passage Center: http://www.fpc.org/adultsalmon/summary_actualreturnsbyspecies.html
[8] Mackie, Richard Somerset. 1997. “Trading Beyond the Mountains: The British Fur Trade on the Pacific 1793-1843.” Vancouver: University of British Columbia (UBC) Press. pp. 191–192; Tidwell, KS. et al. 2017. “Evaluation of pinniped predation on adult salmonids and other fish in the Bonneville Dam tailrace.” U.S. Army Corps of Engineers, Portland District Fisheries Field Unit. Cascade Locks, OR. 54pp.
[9] Newby, T. C. 1973. Changes in Washington State harbor seal population, 1942-1972. Murrelet 54:5-6; Zier and Gayos, 2014. “Harbor seal species profile.” Encyclopedia of Puget Sound. SeaDoc Society/UC Davis’ Karen C. Drayer Wildlife Health Center
[10] Dept. of Fisheries and Oceans. 2010. “Population Assessment Pacific Harbour Seal (Phoca vitulina richardsii).” DFO Can. Sci. Advis. Sec. Sci. Advis. Rep. 2009/011; Zier and Gayos, 2014. “Harbor seal species profile.” Encyclopedia of Puget Sound. SeaDoc Society/UC Davis’ Karen C. Drayer Wildlife Health Center
[11] Laake et al. 2018. “Population Growth and Status of California Sea Lions.” Journal of Wildlife Management, 82(3):583-595; McClatchie et al. 2016. “Food limitation of sea lion pups and the decline of forage off central and southern California.” Royal Society Open Science. https://doi.org/10.1098/rsos.150628
[12] National Marine Fisheries Service. 2013. Status Review of The Eastern Distinct Population Segment of Steller Sea Lion (Eumetopias jubatus). 144pp+ Appendices. Protected Resources Division, Alaska Region, National Marine Fisheries Service, 709 West 9thSt, Juneau, Alaska 99802.
[13] Carretta, J.V. et al. 2019. Sources of Human-related Injury and Mortality for U.S. Pacific West Coast Marine Mammal Stock Assessments, 201-2017. U.S. Department of Commerce, NOAA Technical Memorandum NMFS-SWFSC-616.
[14] Shields MW et al. 2018. “Increased presence of mammal-eating killer whales in the Salish Sea with implications for predator-prey dynamics.” PeerJ6:e6062 http://doi.org/10.7717/peerj.6062
Supporting Organizations
ANIMAL WELFARE INSTITUTE • CETACEAN SOCIETY INTERNATIONAL • CONSERVATION LAW FOUNDATION
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THE HUMANE SOCIETY OF THE UNITED STATES • INTERNATIONAL FUND FOR ANIMAL WELFARE • OCEANA
OCEANIC PRESERVATION SOCIETY • ORCA BEHAVIOR INSTITUTE • ORCA NETWORK • NATURAL RESOURCES DEFENSE COUNCIL NY4WHALES • SANCTUARY EDUCATION ADVISORY SPECIALISTS • WHALE AND DOLPHIN CONSERVATION
