National Marine Mammal Laboratory (NMML)

Polar Ecosystems Program

Habitat Use and Seasonal Movements of Ribbon Seals in the Bering Sea and North Pacific

Figure 3.  An adult male ribbon seal live-captured off the coast of eastern Kamchatka, Russia, and instrumented with a satellite-linked dive recorder.  Photo by Michael Cameron.

In June 2005, researchers from the Polar Ecosystem Program (PEP) successfully live-captured 10 ribbon seals (Histriophoca fasciata) off the coast of eastern Kamchatka, Russia. The seals were captured in hoop nets on the ice floes where they were resting and were physically restrained and instrumented with satellite-linked dive recorders (SDRs) (Fig 3.). The SDRs provide data on a seal’s location and on the timing and depths of its dives. The data, received through the Argos data collections system, can be analyzed to provide: 1) correction factors for seals missed (i.e., not hauled out) during sightings surveys, 2) information on habitat selection (i.e., foraging and haul-out locations) and seasonal movements (i.e., post-molt migration routes), and 3) information on seals’ foraging behavior.

Ribbon seals are an important subsistence resource for some Alaska Native communities and are likely to be a key ecological component of arctic marine ecosystems, yet relatively little is known of their abundance, seasonal distribution, migration, and food habits. The distributions and densities of ice-dwelling seals are highly sensitive to suitable sea ice conditions and, as such, may be particularly vulnerable to climatic change. Changes in sea ice extent have been nonuniform; therefore, the effects on seals are likely to occur on regional scales, emphasizing the need for quality data throughout their range. Some researchers have speculated that most ribbon seals remain in the Bering Sea and become pelagic during the summer, unlike ringed seals (Phoca hispida) that follow the ice edge north as it melts. If true, the impact that ribbon seals may have on the Bering Sea’s invertebrate and fish stocks could be significant.

Preliminary results indicate that these "pagophilic seals" may, after the molt, remain primarily in the ice-free areas south of the Bering Strait. Most seals dispersed southeast into ice-free areas soon after they were tagged, with some adults traveling into the North Pacific and foraging south of the central Aleutian Islands. Most dives were to less than 150 m (perhaps to the seafloor) when over the continental shelf but deepened as seals moved into offshore waters.

The two adult males, three adult females, and five pups outfitted with SDRs represent the first instance of live-capture and instrumentation of ribbon seals. The capture site, in the Russian waters of the western Bering Sea, was particularly favorable for developing new capture techniques because ribbon seals are found there in relatively high densities, within range of small charter vessels. This study demonstrated the feasibility for future studies of ribbon seals in the remote marginal ice zone of the central Bering Sea when opportunities are available to work from large vessels such as the NOAA research vessel Oscar Dyson. The information gathered from these studies will support important initial steps toward developing the basic understanding required for assessment and management of this poorly-known species.

By Michael Cameron


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AFSC Quarterly Research Reports April-June 2005