Poster abstracts and manuscripts from the Third International ...

Baba, Norihisa
85
SESSION II POSTER MANUSCRIPTS
Impacts of Marine Debris
Characteristics of Northern Fur Seals Callorhinus ursinus
Entangled in Marine Debris in the Western North Pacific Ocean
and Okhotsk Sea from 1971 to 1987 and 1993
National Research Institute of Far Seas Fisheries, Shizuoka,
Japan
Abstract
22 (5 males, 17 females) northern fur seals entangled in marine
debris were observed in a total research distance of 69,164 km in
the western North Pacific and Okhotsk Sea during 1971-1983 and
1993. Discovery rate of entangled fur seals were 0.09 to 1.21
seals per 1,000 km (mean ; 0.32). Entanglement rates (percentage
of entangled seals / total observed seals) were 0.01 to 0.23%
(mean 0.06%). Kinds of debris entangled on fur seals were
fishing net fragments, plastic packing bands and cord. Fishing
net fragments accounted for 67% of total debris. Entangled male
seals were 1, 2, and 5 years old and females were 2 to 23 years
old. Juvenile fur seals entangled in marine debris were more
numerous than adults.
Introduction
Northern fur seals, Callorhinus ursinus, were separated roughly
into two groups. One was fur seals bred at Pribilof Islands,
Bogoslof Island, and San Miguel Island, and they migrated mainly
along the continental shelf in the eastern North Pacific. The
other one was fur seals bred at Commander Islands, Kurile
Islands, and Robben Island, and they migrated mainly along the
islands in the eastern North Pacific (Kajimura and Loughlin).
Data on Pribilof fur seals entanglement have been collected
actively at St. Paul Island since the 1960's, in the eastern
Bering Sea and central North Pacific (Scordino, Fowler, Fowler et
al., Dahlberg and Day, Baba et al.). Fowler summarized that the
entanglement rate of juvenile male fur seals at St. Paul Island
was 0.3-0.4%, that 0.2-3.1 trawl net fragments were sighted per
1,000 km research distance and that l0-17% of these fragments
were observed to contain entangled seals. There are few reports
about entanglement of fur seals on Robben Island, Commander
Islands, and Kurile Islands in the literature (Kuzin, Yoshida and
Baba).
Ribic and Swartzman indicated that data of distribution on
oceanic debris and fur seals are needed to evaluate the impact of
entanglement on fur seals. To understand the status of entanglement
on northern fur seals in the North Pacific, information of
entanglement on fur seals in the western North Pacific are
necessary. The purpose of this paper is to determine the
entanglement rate of fur seals in the western North Pacific and