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Alaska Ecosystems Program

Russian Steller Sea Lion Research Update

figure 1, click to enlarge
Figure 1.  Click image to enlarge.

The National Marine Mammal Laboratory (NMML) has a long history of joint research on Steller sea lions in the Russian Far East. Beginning in the early 1990s, NMML scientists and scientists from TINRO (Russian Pacific Federal Fisheries Research Institute, Vladivostok) have worked collaboratively on joint surveys on Soviet scientific expeditions to the Kuril and Aleutian Islands to examine Steller sea lion rookeries and mark pups for estimation of vital rates.

In recent years, this work has continued in cooperation with the Alaska SeaLife Center, Kamchatka Institute of Geography of the Russian Academy of Sciences, and a number of other Russian scientific research institutes and organizations (Sevvostrybvod, TINRO, Komandorsky Reserve, Vyatskaya Agricultural Academy, Pacific Oceanological Institute) under the title of Project 02, "Marine Mammals," a section within Area V of the U.S.-Russia Agreement on Cooperation in the Field of Environmental Protection.

- Abundance Monitoring:

In Russia, aerial surveys of Steller sea lions are not possible due to the lack of appropriate aircraft and the absence of a sufficiently developed network of airports necessary to safely operate, refuel, and maintain planes. Therefore, rookery surveys intended to monitor changes in population trends are conducted from vessels and inflatable boats during the sea lion reproductive period (June–July).

Steller sea lions in Russian waters range over an extremely large area (Fig. 1), such that surveys are staggered among different areas in different years (Table 1). Results of surveys in adjacent years and adjacent areas are combined to determine total population in the region and to estimate trends. Results indicate that abundance varies in different areas (Table 1, Fig. 2).

Table 1.  Counts of Steller sea lions in Russia, June–July 2001–08 (all sites, ages, and sexes combined).
Year Western
Bering Sea
Northern Sea
of Ohkotsk
2001     946   748   6,840   1,160   3,683  
2002 18   774   626       1,451   3,077  
2003     746       6,775   1,599      
2004 135   895   683       1,592   4,346  
2005             7,685   1,625      
2006     931   678       1,590   4,575  
2007             10,185          
2008 110   890   679              

For example, in the western part of the Bering Sea, on the Commander Islands, and along the east coast of Kamchatka, the species' abundance has remained low with an insignificant downward trend after a sharp decrease in the 1980s. At the same time on the Kuril Islands, along the Sakhalin coast and in the northern part of the Sea of Okhotsk, the trend has been positive.

Collectively, data from 2006–08 suggest that about 18,000 sea lions haul out on Russian rookeries during the reproductive period (Table 1). Considering that during the direct survey approximately 30% of the juvenile and adult animals stay in the water and are not counted, the total population of Steller sea lions in Russia can be estimated to be approximately 25,000 animals.

figure 2, see caption
Figure 2.  Changes in abundance of Steller sea lions in Russia, 1960s–2000s (trend sites combined):  NPSO = northern part of the Sea of Okhotsk;
Sakh = Tuleny Island, Sakhalin;  Kurils = Kuril Islands;  CI= Commander Islands;  EK = East Kamchatka;  WBS = western Bering Sea.

There is concern about the low number of breeding Steller sea lions on the coast of east Kamchatka and on the Commander Islands. Although the Commander Islands Steller sea lions inhabit Russian waters, they are genetically part of the western stock that ranges from the Commanders to Cape Suckling, just east of Prince William Sound.  (continued)

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