To Kill Seals and Sea Lions?

The following is intended as a fact-based resource with regard to considerations around killing seals and sea lions off the coast of British Columbia. This resource will be updated with additional research and sources. 

It has been catalyzed by our being asked questions by media and members of the public due to:

(1) The “Proposal for Commercial Harvesting of Pinnipeds* in British Columbia” which has been put forward to Fisheries and Oceans Canada by the Pacific Balance Pinniped Society (PBPS). *”Pinnipedia” is the group name (infraorder) to which seals, sea lions and walruses belong.  The target pinniped species in the Proposal are Pacific Harbour Seals, Steller Sea Lions and California Sea Lions.

(2) Recent shootings and disturbances of pinnipeds leading to increased public attention to seal and sea lion populations in British Columbia.


Examples of March 2019 headlines:


What is the “Proposal for Commercial Harvesting of Pinnipeds in British Columbia”? 

While the Proposal is not currently available to the public, there has been considerable media attention to the Proposal and the Pacific Balance Pinniped Society allowing for the following insights:

  • The Proposal is for a harvest, not for sustenance hunting. Considerations include marketing the meat to China and Europe (Zussman, 2018 and PBPS, 2019). 
  • The rationale provided for the harvest includes the thinking that killing seals and sea lions would leave more Chinook salmon for endangered Southern Resident Killer Whales (currently at only 75 members).
  • Quotes provided by Pacific Balance Pinniped Society board members indicate that the proposal is for killing up to 50 percent of BC’s seals and sea lions (Rasmussen, 2018). 
  • The Proposal would have to receive Federal approval to be exempted from the Marine Mammal Regulations under which it is illegal to harm or disturb a marine mammal. 
  • The Pacific Balance Pinniped Society “was established in July 2018 and includes a number of First Nations, commercial and sport fishers and fur industry representatives” (Larsen, 2019). 
  • The online presence of the Society is via Facebook at this link.

The screen shot above shows abundant sea lions during the fishery for Pacific Herring. It is from a video by Shalaine Lawson posted on social media on March 15th, 2019 . It is included  here to help provide understanding of why there are frustrations and further negative emotions regarding seals and sea lions during these localized events where the overlap between humans and pinnipeds is extreme.

Emotions may be amplified as a result of concern for the endangered Southern Residents and the potential of additional fishing restrictions impacting livelihoods. 

Great caution is required where emotions run high on both sides of an issue and may include animosity and vilification. In such cases, decisions with far-reaching consequences have high risk of  being impacted more by politics and perception, than by facts and precaution.


Are seals and sea lions responsible for the decline in the numbers of endangered Southern Resident Killer Whales?

The number of Pacific Harbour Seals off the coast of British Columbia has not increased  in 20 years. Yet the population of endangered Southern Residents has declined significantly. In fact, the total number of Southern Residents increased for a few years after the number of seals reached carrying capacity. See graphs below. 

The current population size of Pacific Harbour seals, now at carrying capacity, appears to be similar to pre-exploitation levels that occurred in the 1880s when salmon would have been plentiful (Olesiuk, 2010). 

Source of above graph: Chandler et al, 2017.

Image result for graph southern resident killer whales

Source of above graph: Centre for Whale Research, 2019

Above two graphs combined showing Southern Resident Killer Whale population fluctuating while Pacific Harbour Seal population remains constant at carrying capacity.

Steller Sea Lions are protected as a species of Special Concern under Canada’s Species at Risk Act. This means that they are an at-risk species that may become threatened or endangered because of a combination of biological characteristics and identified threats (Fisheries and Oceans Canada, 2010 with reassessment in 2013 and Chandler et al, 2017).

It is worthy of note that research near the Scott Islands, BC (Spalding, 1964) found that there was little evidence that historical culls had positive effects on salmon stocks. As quoted in COSEWIC, 2013 “there is little evidence that Steller Sea Lion control programs had any beneficial effect on fisheries as salmon catches did not increase noticeably following the reduction of sea lion numbers.”

California Sea Lion numbers have increased steadily since the 1970s. The population is reported to have reached carrying capacity as of 2008.  However, research also found that population growth can decrease dramatically with increases in sea surface temperatures (research from NOAA Fisheries’ Alaska Fisheries Science Center and Southwest Fisheries Science Center, NOAA Fisheries, 2018 and Laake et al, 2018).

Source of above graph: NOAA Fisheries, 2018. Caption provided: “California Sea Lion numbers have grown steadily since the 1970s . . . The yellow band reflects the approximate population size, while K represents carrying capacity and MNPL is maximum net productivity level (the population level for maximum growth). The range above MNPL and below K is the optimum sustainable population, which the Marine Mammal Protection Act [USA] sets as the goal for protected species.” 

See further detail on population numbers near the end of this blog.


What are potential unintended impacts for other species?

Impacts to Mammal-Eating Killer Whales

Seals and sea lions are of great importance in the diet of mammal-eating Killer Whales known as Bigg’s Killer Whales (also known as “West Coast Transients”).

This is a distinct population protected as threatened under Canada’s Species at Risk Act. They are genetically, acoustically, and culturally distinct from other Killer Whale populations.

It is believed that reductions in pinniped populations negatively impacted Bigg’s Killer Whales and that their recent resurgence is directly correlated to the number of seals. 

From Ford et al. 2013: “Large scale culls and harvests of pinnipeds in the late 1800s to mid 1900s depleted populations of Harbour Seals and Steller Sea Lions (COSEWIC 2003; Olesiuk 2010). This likely had a major effect on the abundance and distribution of WCT whales [West Coast Transients] in BC waters. Occurrence of WCT whales in the Strait of Georgia has shown a strong increase over the past four decades, associated with the return of Harbour Seal abundance to historical levels in this area (Ford et al. 2007).”
The Recovery Strategy for Bigg’s Killer Whales (West Coast Transients)  includes the following as a recommended approach to address threats and aid in the recovery of this population, indicating that a seal and sea lion harvest would be in violation of this recommendation: “Maintain current harvest restrictions and ensure research, nuisance seal, or other authorized removals do not cause pinniped population level reductions” (Fisheries and Oceans Canada, 2007). 
Harbour Seals compose 52% of Bigg’s Killer Whales’ diet, and Steller Sea Lions compose 13% .Thereby, these two species alone make up 65% of the prey consumed by these whales (Ford et al 2013). 
Though Bigg’s do consume other marine mammal species  (e.g. Harbour Porpoises, Dall’s Porpoises, Pacific White-Sided Dolphins, Minke Whales), the foraging efficiency and energetics for different prey types are not well understood. The size and speed of other potential prey may make it less energetically profitable for Bigg’s Killer Whales to forage on these prey types instead of seals and sea lions. Seals are predictable in where they can be found and do not have defences like the speed of dolphins and porpoises.

Further, maintaining sufficient prey availability for Bigg’s Killer Whales depends on more than just the overall number of seals, seal lions, and other prey species. They also need a sufficiently wide distribution of prey to be able to forage effectively.

Research from Ford et al 2013 that provides insight into why this is needs to be a consideration includes that Bigg’s Killer Whales most often hunt by stealth and surprise attack. Once the element of surprise is gone, with prey knowing their predators are in the area,  it is likely more profitable for a group of Bigg’s Killer Whales to a new area in search of new prey unaware of their presence.
Note that there is considerable misunderstanding of the total number of Bigg’s Killer Whales (West Coast Transients) off the coast of British Columbia. The last published population estimate is 304 individuals in the inner coast subpopulation (DFO, 2013). In addition to this and, importantly, not included in previous WCT population estimates, is knowledge about additional mammal-eating killer whales that are typically much further off BC’s coast i.e. “an additional 217 rarely-seen individuals are considered to be members of the outer coast WCT subpopulation. The inner coast subpopulation appears to be increasing. The status of the outer coast subpopulation is unknown. (DFO, 2013)

Other considerations regarding potential ecosystem impacts? 

Seals and sea lions are opportunistic predators that feed on other fish species, including Hake and Pacific Herring (Barrett-Lennard, 2018)

Hake feed on juvenile salmon. Thereby, a reduction in the number of pinnipeds could lead to an increase in the number of Hake, and thereby fewer salmon. (Barrett-Lennard, 2018)

Pacific Herring compete with juvenile salmon. Thereby, a reduction in the number of pinnipeds could lead to an increase in this salmon predator at salmon at a critical stage of their development. (Barrett-Lennard, 2018)

Note that there are more than 135 other species that predate on salmon in addition to seals and sea lions (Wallace, 2018).

For further understanding of how to assess potential success of harvests or culls, please see the video and table below from the presentation Will Seal Culls Save the Southern Resident Killer Whales by Dr. Lance Barrett-Lennard of the Coastal Ocean Research Institute provided at the 26th Annual BC Marine Mammal Symposium on November 24th, 2018.

 

Do seals and sea lions eat a lot of salmon? 

Some seals and sea lions in some areas eat a lot of salmon (and herring).

However, caution is very much needed in extrapolating these localized and seasonal studies to inform management decisions across larger geographic areas for larger units of time.

For example: Preliminary research by Sheena Majewski, DFO,  using DNA analysis of non-estuary seal scat samples, reveals the following shift in diet between spring and fall. (Pynn, 2018).

Further research is being conducted to better inform coast-wide and year-round understanding of seal and sea lion diet to address knowledge gaps. As per the information above however, due to the complexity of marine food webs, there will always be some uncertainty about their diet and how it impacts other species.

Further detail on population numbers and history of culling pinnipeds in British Columbia:

Updated estimates based on 2016-17 data anticipated for this fall/winter (2019). 

“The Pacific Harbour Seal population in B.C. suffered significant declines as a result of commercial fur harvests (1879- 1914, 1962-1968) and predator control programs (1914-1964). By the time the species was first protected in B.C. in 1970, the coast-wide population had been reduced to an estimated 10,000 seals, but it has since increased dramatically (Majewski & Ellis In press). Current coast-wide abundance (approximately 105,000 seals) is considered to represent a successful recovery to pre-exploitation levels (Majewski & Ellis In press). In the Strait of Georgia, Harbour Seal numbers grew at a rate of 11.5% annually (95% CI 10.9-12.6%) from 3,600 individuals in 1973 to 39,000 in the mid-1990s, when numbers stabilized (Majewski & Ellis In press; Figure 25-3).”  (Chandler et al, 2017).

“Steller Sea Lions were depleted by commercial harvesting and predator control programs that removed 55,000 animals between 1912 and 1968. By the 1970s, the B.C. breeding population had been reduced to 25-33% of peak historic levels (Olesiuk, 2018). The population began rebounding in the early 1970s, with non-pup numbers shifting from stable to 4.9% growth annually in the early 1980s (Figure 25-4). Pup abundance also exhibited an increase in annual growth rate in the mid-1980s, up from about 1.7 to 7.0% per year (Olesiuk In press). The summer 2013 breeding season survey estimated 39,200 (95% CI 33,600-44,800) Steller Sea Lions coast-wide, slightly lower than the winter 2009-2010 population estimate of 48,000 (95% CI 38,100-58,900) (Olesiuk, 2018). The Steller Sea Lion was designated as Special Concern by COSEWIC in both 2003 and 2013, and has also been legally listed under SARA at the same level” (Chandler et al, 2017).

“Market hunting, bounties, pollutants such as DDT and other forces depressed [California] sea lion numbers in the middle of the last century . .  the species then rose from less than 90,000 animals in 1975 to an estimated 281,450 in 2008, which was roughly the carrying capacity for sea lions in the California Current Ecosystem at that time. It then fluctuated around that level, reaching a high of 306,220 in 2012 before declining below the carrying capacity in the years since as ocean conditions changed” (NOAA Fisheries, 2018).


Sources:

Badelt, Brad. (2018, September 4). Are There Too Many Harbour Seals in British Columbia? Hakai Magazine.

Barrett-Lennard, L. (2018, November 24). Will Seal Culls Save the Southern Resident Killer Whales? Presentation provided at the 26th Annual BC Marine Mammal Symposium.

Center for Whale Research. (2019, January 16). Southern Resident Killer Whale Population. Retrieved from https://www.whaleresearch.com/orca-population.

Chandler, P.C., King, S.A., and Boldt, J. (Eds.). 2017. State of the physical, biological and selected fishery resources of Pacific Canadian marine ecosystems in 2016. Can. Tech. Rep. Fish. Aquat. Sci. 3225: 243 + vi p.

COSEWIC. 2013. COSEWIC assessment and status report on the Steller Sea Lion Eumetopias jubatus in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. xi + 54 pp.

Fisheries and Oceans Canada. 2007. Recovery Strategy for the Transient Killer Whale (Orcinus orca) in Canada. Species at Risk Act Recovery Strategy Series. Fisheries and Oceans Canada, Vancouver, vi + 46 pp.

Fisheries and Oceans Canada. 2010. Management Plan for the Steller Sea Lion (Eumetopias jubatus) in Canada [Final]. Species at Risk Act Management Plan Series. Fisheries and Oceans Canada, Ottawa. vi + 69 pp.

Fisheries and Oceans Canada. 2010. Population Assessment Pacific Harbour Seal (Phoca vitulina richardsi). DFO Can. Sci. Advis. Sec. Sci. Advis. Rep. 2009/011.

Fisheries and Oceans Canada. 2013. Information in Support of the Identification of Critical Habitat for Transient Killer Whales (Orcinus orca) off the West Coast of Canada. DFO Can. Sci. Advis. Sec. Sci. Advis. Rep. 2013/025.

Fisheries and Oceans Canada. 2018. Amended Recovery Strategy for the Northern and Southern Resident Killer Whales (Orcinus orca) in Canada. Species at Risk Act Recovery Strategy Series, Fisheries & Oceans Canada, Ottawa, ix + 83 pp.

Ford, J.K.B., G.M. Ellis, and J.W. Durban. 2007. An assessment of the potential for recovery of West Coast transient killer whales using coastal waters of British Columbia. DFO Can. Sci. Advis. Sec. Res. Doc. 2007/088. Iv + 34 pp.

Ford, John & Stredulinsky, Eva & Towers, Jared & M. Ellis, Graeme. (2013). Information in Support of the Identification of Critical Habitat for Transient Killer Whales (Orcinus orca) off the West Coast of Canada.

Gammon, Katherine. (2018, October 16). Herschel, the Very Hungry Sea Lion – It’s dangerous to blame the decline of one species on a single predator. We humans like to do it anyway. Hakai Magazine.

L. Laake, Jeffrey & S. Lowry, Mark & L. Delong, Robert & R. Melin, Sharon & Carretta, James. (2018). Population growth and status of California sea lions: Status of California Sea Lions. The Journal of Wildlife Management. 10.1002/jwmg.21405.

Larsen, Karin. (2019, February 7). B.C. group hopes commercial seal hunt gets green light. CBC News. Retrieved from www.cbc.ca/news/canada/british-columbia/commercial-seal-hunt-dfo-1.5007895

NOAA Fisheries. (2018, January 17). California Sea Lion Population Rebounded to New Highs. Retrieved from https://www.fisheries.noaa.gov/feature-story/california-sea-lion-population-rebounded-new-highs 

Olesiuk, P.F. 2010. An assessment of population trends and abundance of harbour seals (Phoca vitulina) in British Columbia. DFO Can. Sci. Advis. Sec. Res. Doc. 2009/105. vi + 157 p.

Olesiuk, P.F. 2018. Recent trends in Abundance of Steller Sea Lions (Eumetopias jubatus) in British Columbia. DFO Can. Sci. Advis. Sec. Res. Doc. 2018/006. v + 67 p.

Pynn, Larry. (2018, January 12). Behind the Blubber – Harbor seals are blamed for chinook and coho salmon declines, but ecosystems are more complicated than some suggest. Hakai Magazine.

Rasmussen, Greg. (2018, September 12). B.C. group wants to kill seals and sea lions to save the whales. CBC News. Retrieved from www.cbc.ca/news/canada/british-columbia/b-c-group-kill-seals-save-whales-1.4818745 

Ross, Peter & Barrett-Lennard, Lance. (2018, July 30). Peter Ross and Lance Barrett-Lennard: Harbour seals are easy scapegoats in Chinook salmon decline. Vancouver Sun. Retrieved from https://vancouversun.com/opinion/op-ed/peter-ross-and-lance-barrett-lennard-harbour-seals-are-easy-scapegoats-in-chinook-salmon-decline.

Spalding, D. J. 1964b. Comparative feeding habits of the fur seal, sea lion and harbour seal on the British Columbia coast. Fisheries Research Board of Canada Bulletin 146:1-47.

Wallace, Scott. (2018, December 23). Island Voices: Ideology, not ecology, guiding sea-cull decisions. Times Colonist.

Zussman, Richard. (2018, July 20). New group calls for seal and sea lion cull on B.C.’s coast. Global News. Retrieved from https://globalnews.ca/news/4344527/new-group-seal-sea-lion-cull-bc-coast/