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Steller Sea Lion Survey on Kuril and Iony Islands, Russia

  picture of Steller sea lion
Figure 1. Steller sea lion rookeries and haulouts
along the coast of Asia.

by Vladimir N. Burkanov

Scientists from the United States, Japan, and Russia conducted Steller sea lion (Eumetopias jubatus) research in remote and hard to access areas of the Russian Far East aboard the Russian fish cargo vessel MTR Bolsheretsky from 23 June through 22 July 2001. Forty-six of 59 sea lion rookeries and haul-out sites were surveyed.  A total of 4,897 Steller sea lions age 1+ years old and 1,896 pups were counted on all rookeries in the Kuril Islands; 1,509 non-pups and 952 pups were counted on Iony Island, and 119 non-pups were counted along the southeastern coast of the Kamchatka Peninsula.  Two hundred fifty-seven branded or flipper-tagged animals from previous years were resighted; 480 scat samples were collected throughout the surveyed sites; blood samples were taken from 335 pups (50-60 samples per rookery), and 129 skin punches from the rear flippers of these pups were taken for nuclear DNA analysis; 619 pups were branded, and of these, 572 were simultaneously tagged with paired plastic tags.  All the data collected during this expedition are being analyzed.  A full report will be prepared after all analyses are completed.


  Steller sea lion non-pup counts on Kuril Islands trend sites Figure 2.  Non-pup counts of Steller sea lions on 16 trend sites
on the Kuril Islands, 1955-2001.

Steller sea lion non-pup counts on Kuril Islands rookeries Figure 3.  Non-pup counts of Steller sea lions on the five major
rookeries on Kuril Islands, 1955-2001.

Steller sea lion non-pup counts on Kuril Islands haulout sites Figure 4.  Non-pup counts of Steller sea lions on 11 trend
haulout sites on the Kuril Islands, 1955-2001.

Steller sea lion pup counts on Kuril Islands rookeries Figure 5.  Pup counts of Steller sea lions on the five major
rookeries on the Kuril Islands, 1955-2001.

Iony Island Steller sea lion counts Figure 6.  Steller sea lion counts on Iony Island, 1930-2001.

Map of Kuril Islands branded Steller sea lion movements Figure 7.  Movements of branded Steller sea lions born on the Kuril Islands in 1989-99.


Steller sea lions are widely distributed along the Asian coast, from the China coastline to the Bering Strait.  However, the major breeding areas are located on the Kuril Islands (Figure 1 above), where up to 50 percent or more of the total number of pups are born every year.  The Kuril grouping of Steller sea lions has always been the most abundant on the Asian coast.  The first reported abundance estimates of Steller sea lions at the Kuril Islands were made by visual assessment from a captain of a hunting schooner, (Snow 1902) According to him, at the end of the nineteenth century the Steller sea lion population in the Kuril Islands was about 100,000 animals.  However, all the later data showed that his estimate was too high.  The first and most complete survey of the islands was carried out by a special expedition of the Russian Academy of Sciences in 1955.  The abundance of Steller sea lions (1 year old and older) at that time was estimated at 15,000-17,000 animals throughout the Kuril Islands range.  The first pup counts at the Kuril Islands occurred in 1963.  A total of almost 3,500 new-born pups were counted at all the rookery sites.  These data are the earliest figures on abundance of Steller sea lions in the Kuril population that can be used for comparative analysis.  Later counts of Steller sea lions were carried out concurrently with surveys dedicated to research on northern fur seals (Callorhinus ursinus) and sea otter (Enhydra lutris).  These surveys were carried out somewhat later in the year than the optimal period for counting Steller sea lions (late May to early June), and often not all the sites were surveyed.  Therefore, the acquired data are difficult to analyze and required an estimation of data on sites that were not surveyed.  The most complete data are counts of pups and non-pup sea lions on major rookery sites while data on haulouts are the most irregular (Figures 2-5).

The first data collected on the abundance of Steller sea lions on Iony Island are attributed to the 1930s.  At that time harvesting of Steller sea lions was carried out on the island.  During one of the first harvesting voyages an accurate count of new-born pups took place.  In 1933 at all rookeries around the island 1,510 pups were  counted.  The abundance of mature animals was estimated as 2,000-5,000.  Later counts of Steller sea lions on Iony Island took place in 1948, 1974, 1989, and 1997 (Figure 6).  In 1989 Russian and U.S scientists launched a program of marking Steller sea lions to study migration and  survival and to evaluate the extent of isolation at individual rookeries.  A total of 3,070 pups have been branded/tagged over 10 years, and of these, 368 have been resighted.  Movement patterns determined from these studies show that Steller sea lions travel along the Asian coastline, and animals born on the Kuril Islands have been resighted from the Yellow Sea (China coast) to the Bering Sea (Karaginsky Gulf) (Figure 7).

In 2001 a group of scientists from Russia, Japan and the United States (with financial support provided by the National Marine Mammal Laboratory, Alaska Sealife Center, and Amway Nature Center, Japan)  conducted observations of Steller sea lions and collected biological data at most rookeries and haul-out sites along the Kuril Islands and on Iony Island.  Major tasks were to conduct detailed counts of Steller sea lions for current abundance estimates, search for tagged/branded animals, and measure and  tag/brand 500 new-born pups at five major rookeries in the Kuril Islands and 150 pups on Iony Island. Additional tasks were to collect data on pup morphometry, take blood samples to analyze pup health, and study the extent of isolation of reproductive groupings  by electrophoresis of serum and erythrocytes.  Skin samples also were collected to evaluate by nuclear DNA the extent of isolation at rookeries. 

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