Habitat Use and Seasonal Movements of Bearded Seals in Kotzebue Sound
Figure 2. (Top) Researchers glue a satellite-linked dive recorder to a bearded seal pup. (Bottom) Closeup of a young-of-the-year bearded seal pup just before release.
In October 2006, five male and four female young-of the-year bearded seals, Erignathus barbatus, were captured in Kotzebue Sound, Alaska, and instrumented with satellite-linked dive recorders (SDRs) (Fig. 2 ). Together with an additional 9 female and 8 males tagged in 2004 and 2005, these 26 bearded seals are the first to be instrumented with SDRs in Alaska.
The project was part of a cooperative effort with the Native village of Kotzebue, the University of Alaska, Fairbanks, the Alaska Department of Fish and Game, and the NMML Polar Ecosystems Program, and was funded in part by a tribal wildlife grant from the U.S. Fish and Wildlife Service. It is intended to combine local knowledge about the distribution and habits of bearded seals with the field techniques and analysis expertise of biologists.
Bearded seals are an important Alaska Native subsistence resource and live and reproduce in pack ice habitat. They are also a key ecological component of arctic marine ecosystems and, because they are sensitive to suitable sea ice conditions, may be particularly vulnerable to climatic change. However, little is known of their seasonal movements, habitat use, or diving behavior. The SDRs, which fall off when the seals molt in the spring, provide information on the animals’ movements and can be used to identify important habitats, describe foraging behavior, and improve abundance estimation techniques.
Seals were captured in large-mesh nets set in the shallow, open waters near Kotzebue. Soon after being released, most animals left Kotzebue Sound. Pups occupied areas as far north as Wainwright, Alaska, as far south as St. Lawrence Island, Alaska, and west beyond the Gulf of Anadyr, Russia (Fig. 3.) Analyses of diving data indicate that most dives lasted from 4 to 6 minutes and, while most pups spent almost half of their total time near the seafloor, the amount of time spent at the bottom varied between individuals and with the season and time of day. Haul-out time also varied with season and time of day.
Movement and diving data are still being recorded from instrumented animals. Five of the seals in 2006 had SDRs that also record water temperature and salinity throughout a dive. Correlating these environmental characteristics, as well as bathymetry, ice concentration, and ice extent, with diving behavior will further improve our understanding of the important foraging habitats of young bearded seals.
Figure 3. Map of the current tracks of bearded seals instrumented in 2006. Callouts indicate the last know position at the given date.
By Michael Cameron
Workshops and Meetings
Staff from the Polar Ecosystems Program (PEP) participated in several workshops and comanagement meetings during the past quarter. In a meeting with the Ice Seal Committee (ISC), an Alaska Native organization representing subsistence hunters of ice seals, PEP members reported on results from satellite telemetry studies of bearded, spotted, ribbon and ringed seals, and participated in the signing of a new comanagement agreement between NMFS and the ISC.
Another new marine mammal comanagement agreement was signed with the Aleut Marine Mammal Commission (AMMC). PEP staff provided an update on harbor seal research to the AMMC annual board meeting.
