Trends in abundance of Steller sea lions and northern fur seals across the North Pacific Ocean Rolf R. Ream National Marine Mammal Laboratory, NMFS, Seattle, WA Vladimir Burkanov Natural Resources Consultants, Inc., Seattle, WA
Steller sea lion and northern fur seal range Steller sea lion range Northern fur seal range
Yellow dots = Steller sea lions Pink dots = Northern fur seals
Pribilof Island northern fur seal at-sea distribution Winter Summer Migration Breeding (November-June) (June-November)
Steller Sea Lion Rookeries and Stock Structure Eastern Stock Thousands 16 14 SE AK 12 1 8 6 4 2 BC OR & CA 197 198 199 2
Non-Pup Steller Sea Lion Counts 8, 7, 6, 5, 4, 3, 2, 1, Kenai-to-Kiska Rookeries Trend Rookeries and Haulouts All Surveyed Sites 1985 1987 1989 1991 1993 1995 1997 1999 21 23 25
Non-Pup Steller Sea Lion Counts 2% % 1991-2 1% 8% 2-24 -2% -4% -6% -8% -1% -12% -14% 6% 4% 2% % -2% -4% -16% Aleutian Islands Gulf of Alaska Western Central Eastern Western Central Eastern -6% Aleutian Islands Gulf of Alaska Western Central Eastern Western Central Eastern Annual Rates of Change Mean ± 95% CI
Historic Changes in Distribution and Abundance of Steller Sea Lions in the Western Pacific, 17s 22 Steller sea lion rookeries and houlouts along Asia coast, 17s-22
Steller sea lion rookeries and haulouts along Asia coast, 17s-22 Counts at 6 trend sites in the WBS, age 1+ 6, 5, 4, 3, 2, 1, 1982 1984 1986 1988 199 1992 1994 1996 1998 2 22
EK: ABUNDANCE & TRENDS, 1982-22: Counts at 8 trend sites in EK, 1983-22 (age 1+) N u m b e r, a g e 1 + 2,5 2, 1,5 1, 5 1983 1985 1987 1989 1991 1993 1995 1997 1999 21
CI: ABUNDANCE & TRENDS, 193-22: Counts of SSL in Commander Islands, 193-22 (age 1+) 6, 5, 4, 3, 2, 1, 193 194 195 196 197 198 199 2
Kuril Islands trend sites: 1955-21 Historic Changes in Distribution and Abundance of Steller Sea Lions in the Western Pacific, 17s 22 Steller sea lion abundance in Kuril Islands, 189-21 25, 2, 15, Individuals 1, 5, 1, 8, 6, 4, 2, 1955 196 1965 197 1975 198 1985 199 1995 2 188 19 192 194 196 198 2
Historic Changes in Distribution and Abundance of Steller Sea Lions in the Western Pacific, 17s 22
Historic Changes in Distribution and Abundance of Steller Sea Lions in the Western Pacific, 17s 22 Tuleny I. 14 12 1 Non-pup 8 6 4 2 1955 196 1965 197 1975 198 1985 199 1995 2 NON-PUP
Historic Changes in Distribution and Abundance of Steller Sea Lions in the Western Pacific, 17s 22 THE NORTHERN PART OF THE SEA OF OKHOTSK: 1931-22 8 7 6 5 4 3 2 1 193 194 195 196 197 198 199 2 Total abundance
Reconstructed Steller sea lion abundance along Asian Reconstructed Steller sea lion abundance along Asian coast, coast, 188-2 196-2 12, 3, 1, 25, 2, 8, 15, 6, 1, 5, 4, 2, 196s 197s 198s 199s 2s 189s 191s 193s 196s 198s 2s
Summary of SSL along the Asian coast Steller sea lion abundance declined from a maximum of 115, to 15, individuals from 189 to 199; early decline likely influenced by harvests at some sites Changes in abundance occurred during all time periods but varied by site and period. Recent increases observed in Okhotsk region Southern extent of Steller sea lion distribution has moved north by some 5-9 km over the past 5 years
Northern Fur Seal Breeding Sites Russia North America Commander Islands Robben Island Pribilof Islands Bogoslof Island San Miguel Island Kuril Islands
Current worldwide population size ~1.1 million Commanders 2.6% Pribilofs 52.6% Kurils 1.2% Robben 11.5% Bogoslof 4.5% San Miguel.7%
NFS harvest on Pribilof Is., 1911-1984 1984 Males Killed (thousands) 1 9 8 7 6 5 4 3 2 1 Commercial Harvest St. Paul St. George 191 192 193 194 195 196 197 198 Juvenile males Females Killed (thousands) 4 35 3 25 2 15 1 5 St. Paul St. George St. Paul (Commercial) St. George (Commercial) Year Females: ~32, 1956-1968 Pelagic collections for science: >38, 1915 193 1945 196 1975 Year 1958-1974
Pribilof Islands pup production, 1912-24 24 5 1 St. Paul Production (1,s) 45 4 35 3 25 2 15 1 5 St. Paul St. George 1998-24: - 6.2% / yr 9 8 7 6 5 4 3 2 1 St. George Production (1,s) 19 192 194 196 198 2 22 Year
Bogoslof Island Pup Production 14 12 Number of Pups 1 8 6 4 2 1997-25 +12% / yr 198 1985 199 1995 2 25 Year
San Miguel Island (California) Pup Production 35 3 25 Adams Cove Castle Rock Total Production Number of pups 2 15 1 5 197 1975 198 1985 199 1995 2 25 Year
NFS distribution in Russia Tuleny (Robben) Island Kuril Islands Commander Islands
Commander Islands: 1958-24 +.5 % year 1995-24 - 2.1 % year ALL rookeries pups born, 1958-24 8 7 6 5 4 3 2 1 1958 1963 1968 1973 1978 1983 1988 1993 1998 23
Tuleny pups born 1995-24 + 7.8 % year 6 5 4 3 2 1 1958 1963 1968 1973 1978 1983 1988 1993 1998 23 3 Kuril I. pups, 1958-25 1988-25 + 4.4 % year 25 2 15 1 5 1958 1963 1968 1973 1978 1983 1988 1993 1998 23
Summary of NFS trends Some past declines largely influenced by harvests Female harvest on the Pribilofs; ; may have affected other populations Recently: Declines in the Bering Sea Substantial increases at Tuleny, Kuril,, and Bogoslof Islands
Using pinniped population trends as indicators of ecosystem change Use of historical data complicated by: Gaps in time series Effects of harvests Current/future data promising. Needs: Assess influence of human activities on population trends (development, fishing, etc.) Consider other population characteristics Demographic: trends may be driven by changes in age structure (A. Kuzin; ; NFS at Tuleny I.) Behavioral: seasonal geographic distribution
Спасибо! E-mail: Rolf Ream rolf.ream@noaa.gov Vladimir Burkanov: vburkanov@nrccorp.com