ISSN 10630740, Russian Journal of Marine Biology, 2014, Vol. 40, No. 7, pp. 532–538. © Pleiades Publishing, Ltd., 2014.
Original Russian Text © A.E. Kuzin, 2014, published in Izvestiya TINRO.
Tyuleniy Island in Sakhalin Oblast is a breeding
ground for the northern fur seal and steller sea lion, as
well as grounds that are used by the spotted seal to rest
and molt . These animals stay on the island from
early spring to late fall. In the winter, the sea water
around the island freezes; fur seals and sea lions
migrate southward, whereas spotted seals disperse over
the adjacent waters, lying on the ice.
The goal of this work is an assessment of the
presentday abundance and distribution of pinnipeds
on Tyuleniy Island.
MATERIALS AND METHODS
In 2013, a pinniped survey on Tyuleniy Island was
conducted from June 14 to July 25 that covered the
entire breeding season for the northern fur seal, the
peak of pupping for the steller sea lion, and the post
breeding period for the spotted seal. Fur seals were
counted during the morning hours (from 5:00 to
8:30 a.m.); sea lions were counted twice a day (from
5:00 to 8:30 a.m. and from 15:30 to 18:30);
spotted seals were counted several times a day, every
3–4 hours. This schedule of surveys was determined by
the necessity to have important information on the
sizes of certain age categories of animals (fur seal pups
and bulls as well as sea lion females and pups) or by the
dependence of the haulouts of the animals on tidal
currents (for the spotted seal).
For comparison, we also used data from studies
that were conducted in previous years.
RESULTS AND DISCUSSION
The Northern Fur Seal
The maximum counted number of adult fur seals
on Tyuleniy Island in 2013 was 43000 individuals
The largest number of bulls, 5000, was recorded on
July 18; the largest number of harem bulls, 1124,
occurred on July 15. The ratio was one harem bull to
4.4 nonharem bulls. The maximum number of
females, 30300 individuals, which was recorded on
July 12, was almost 30% of the total population. The
bull to female ratio was 1.0 : 6.1; the harem bull to
female ratio was 1.0 : 26.9 (at the allowable normal
ratio of 1.0 : 40.0). The number of counted pups (on
July 23) was 34700 (31500 live and 3200 dead).
The number of halfbulls was 2600, while there were
5000 bachelors. The size of the population was esti
mated at 115000 individuals.
The distribution of animals over the island was as
follows: 73.4% of the female fur seals occupied the
eastern beach of the island, 12.6% occupied the upper
plateau, 8.5% occupied the southern cape, and 5.5%
New Data on the Abundance of the Northern Fur Seal (
), Steller Sea Lion (
), and Spotted Seal
) on Tyuleniy Island, Sea of Okhotsk
A. E. Kuzin
Pacific Research Fisheries Center, per. Shevchenko 4, Vladivostok, 690091 Russia
Received April 24, 2014
—The latest data on the abundance and distribution of the northern fur seal (
steller sea lion (
), and spotted seal (
) on Tyuleniy Island (Sea of Okhotsk) are
presented. Based on the surveys in June and July of 2013, the total estimated number of northern fur seals is
115000. The direct counts showed 5000 bulls, 30300 females, and 34700 pups (31500 live and 3200 dead).
The total decrease in the number of females and pups for the recent 4 years is 18.0% (or 4.5% per year). The
counted number of Steller sea lions is 1879 adults, viz., 119 bulls, 1390 females (of which 68.5% were parous),
and 370 animals of other categories. A total of 890 pups were recorded. The reproductive group of sea lions is
increasing due to immigrants. The largest number of spotted seals is 162 individuals. Its seasonal and daily
variations are dynamic.
: northern fur seal, steller sea lion, spotted seal, abundance, distribution, Tyuleniy Island