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What Else is Eating Chinook and How Much are they Eating? John Ford Pacific Biological Station Fisheries and Oceans Canada Nanaimo, British Columbia.

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Presentation on theme: "What Else is Eating Chinook and How Much are they Eating? John Ford Pacific Biological Station Fisheries and Oceans Canada Nanaimo, British Columbia."— Presentation transcript:

1 What Else is Eating Chinook and How Much are they Eating? John Ford Pacific Biological Station Fisheries and Oceans Canada Nanaimo, British Columbia

2 Competition for SRKW Chinook by other predators Only concerned with 3–6 yr old Chinook Potential competitors: »Other killer whale populations »Salmon shark »Harbour seal »California sea lion »Steller sea lion

3 Killer whale Orcinus orca

4 NRKW and SRKW mostly allopatric in summer and fall, extent of overlap in winter/spring unknown Northern (n = 4,765 encounters) Southern (n = 12,956 encounters) Sources: Ford 2006 CSAS Res Doc 2006/072; Whale Museum, Friday Hbr; L. Barre, NOAA

5 Percent Month Locations of sampling, stock regions, and monthly distribution of Chinook salmon sampled from feeding events by northern resident killer whales in the northern Queen Charlotte Islands (PFMA 1). n = 33 NRKW prey on many of the same stocks as SRKW

6 Significant overlap off southwestern Vancouver Island Competition in important feeding area Days with detections from Aug 2009 to Jul 2010: 80 SRKW, 54 NRKW Days with detection Source: Riera, Ford & Chapman. in prep.

7 Salmon shark Lamna ditropis D. Perrine

8 Salmon shark are wide ranging, tend to move north in summer D. Perrine Source: Weng et al MEPS

9 Salmon shark Feeds on a wide variety of fishes and squids Salmon is preferred prey during summer months in coastal waters Sockeye comprises majority of prey in NE Pacific; Chinook predation appears minor Abundance and trend poorly known Some anecdotal evidence that abundance may be increasing, but overall probably lower than 50 years ago

10 Harbour seal Phoca vitulina

11 Harbour seal haulout sites in British Columbia Distribution: Harbour seal DFO Population Assessment Pacific Harbour Seal (Phoca vitulina richardsi). DFO Can. Sci. Advis. Sec. Sci. Advis. Rep. 2009/011.

12 Population severely depleted by control programs and harvest, ended in 1970 Abundance increased 10-fold since early 1970s Increased at 11.5% per year before stabilizing in 1990s Current abundance: ca. 40,000 Strait of Georgia, 32,000 Washington DFO Population Assessment Pacific Harbour Seal (Phoca vitulina richardsi). DFO Can. Sci. Advis. Sec. Sci. Advis. Rep. 2009/011. Status: Harbour seal Strait of Georgia Jeffries et al Trends and Status of Harbor Seals in Washington State: J. Wild. Manage.

13 Percent of overall diet Average prey composition for harbour seals, Strait of Georgia (n = 2,841 scat samples, collected ) Olesiuk, P.F Annual prey consumption by harbor seals (Phoca vitulinaJ in the Strait of Georgia, British Columbia. Fish. Bull. 91: Diet: Harbour seal

14 Recent scat studies by WDFW in San Juans show adult salmon in 58% of scats in summer/fall, 11% in winter, and 4% in spring Of 76 salmon IDd from otoliths, 7 (9%) were Chinook Scat studies in 2011 by Austen Thomas, UBC, in Fraser River estuary and western Strait of Georgia show diets dominated by pink salmon, no Chinook detected. Acevedo-Gutiérrez et al.s recent studies (document on ESSA website) suggest harbour seal diet in San Juan Islands may be composed of 3-17% Chinook salmon; whales may take (1030 ± 223) tonnes of adult Chinook (based on estimate from fatty acid signatures) Harbour seal: recent diet studies

15 California sea lion Zalophus californianus 15

16 Status: California sea lion Abundance increased from 50,000 in 1975 to 297,000 in 2010 Males migrate to Washington, southern coast of Vancouver Island and the Strait of Georgia during winter Wintering animals started appearing in BC during 1960s, peaked at 4500 in 1984, declined to 1500 by

17 California sea lion abundance and distribution Wintering haul out sites for California sea lions Olesiuk, P.F Status of sea lions (Eumetopias jubatus and Zalophus californianus) wintering off southern Vancouver Island. Natl Marine Mammal Peer Review Committee Working Paper. 17

18 California sea lion abundance and distribution Abundance of California sea lions, Olesiuk, P.F Status of sea lions (Eumetopias jubatus and Zalophus californianus) wintering off southern Vancouver Island. Natl Marine Mammal Peer Review Committee Working Paper. 18

19 Diet composition of sea lions wintering off southern Vancouver Island Olesiuk, P.F. and M.A. Bigg Seals and sea lions on the British Columbia coast. DFO/4101, Pacific Biological Station Percent of overall diet Diet: California sea lions in winter 19

20 Steller sea lion Eumetopias jubatus

21 Population depleted to 25-30% of historical abundance by control programs and harvests, Abundance increasing at 3.5% per annum (5% in recent years) Numbers in B.C. currently range from 32,000 in summer to 48,000 in winter Olesiuk, P.F Abundance of Steller sea lions (Eumetopias jubatus) in British Columbia. Can. Science Advisory Sec., Fisheries and Oceans Canada, Ottawa. Res Doc 2011/000. Status: Steller sea lion

22 Population depleted to 25-30% of historical abundance by control programs and harvests, Abundance increasing at 3.5% per annum (5% in recent years); eastern stock now about 53,000 Numbers in B.C. currently range from 32,000 in summer to 48,000 in winter Olesiuk, P.F Abundance of Steller sea lions (Eumetopias jubatus) in British Columbia. Can. Science Advisory Sec., Fisheries and Oceans Canada, Ottawa. Res Doc 2011/000. Status: Steller sea lion Historic Total Counts (1913)

23 Steller Sea Lion - Seasonal Distribution SummerFall Olesiuk, P., and J. Ford Hypothesis: Predation by marine mammals is an important contributor to the Fraser sockeye situation. Presentation to Sockeye Situation Working Group, Pacific Biological Station.

24 Steller Sea Lion - Seasonal Distribution WinterSpring Olesiuk, P., and J. Ford Hypothesis: Predation by marine mammals is an important contributor to the Fraser sockeye situation. Presentation to Sockeye Situation Working Group, Pacific Biological Station.

25 Steller Sea Lion - Daily Prey Requirements estimated by P. Olesiuk, DFO Young-of-year: 4 kg to 15 kg by first spring (17-23% body mass) Adult females: 15 kg (16 kg pregnant; perhaps up to 30 kg while lactating) (5.3% body mass) Adult males: 28 kg (15 kg summer to kg outside breeding season) (4.1% of body mass) Overall per capita: 18 kg Annual Consumption: 161,000 tonnes (CV ~22-25%) Olesiuk, P., and J. Ford Hypothesis: Predation by marine mammals is an important contributor to the Fraser sockeye situation. Presentation to Sockeye Situation Working Group, Pacific Biological Station.

26 Seasonal Prevalence of Salmon Olesiuk, P., and J. Ford Hypothesis: Predation by marine mammals is an important contributor to the Fraser sockeye situation. Presentation to Sockeye Situation Working Group, Pacific Biological Station. Jeffries, S Trends in other Chinook salmon predators. Presentation to NOAA-DFO Killer Whale – Chinook Workshop 1, Sept 2011

27 Proportion of Salmon in Diet Annual Salmon Consumption: 17,200 tonnes (CV ~ ) Olesiuk, P., and J. Ford Hypothesis: Predation by marine mammals is an important contributor to the Fraser sockeye situation. Presentation to Sockeye Situation Working Group, Pacific Biological Station.

28 Species of Salmon (DNA) (Preliminary results based on 1/3 of available samples analyzed to date) Olesiuk, P., and J. Ford Hypothesis: Predation by marine mammals is an important contributor to the Fraser sockeye situation. Presentation to Sockeye Situation Working Group, Pacific Biological Station. Jeffries, S Trends in other Chinook salmon predators. Presentation to NOAA-DFO Killer Whale – Chinook Workshop 1, Sept 2011

29 Species of salmon in Steller sea lion scat Summer: Jeffries, S Trends in other Chinook salmon predators. Presentation to NOAA-DFO Killer Whale – Chinook Workshop 1, Sept 2011

30 Species of salmon in Steller sea lion scat Fall: Jeffries, S Trends in other Chinook salmon predators. Presentation to NOAA-DFO Killer Whale – Chinook Workshop 1, Sept 2011

31 Species of salmon in Steller sea lion scat Winter: Jeffries, S Trends in other Chinook salmon predators. Presentation to NOAA-DFO Killer Whale – Chinook Workshop 1, Sept 2011

32 Species of salmon in Steller sea lion scat Spring: Jeffries, S Trends in other Chinook salmon predators. Presentation to NOAA-DFO Killer Whale – Chinook Workshop 1, Sept 2011

33 Conclusion: Steller sea lion Opportunistic predators and consume all species of salmon and wide variety of other prey Salmon a significant component of diet Increasing abundance of sea lions likely associated with increasing predation rates on salmon


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