Abundance and distribution of harbor seals from Icy Bay to Icy Strait, Southeast Alaska during August 1996, with recommendations for a population trend route
Mathews EA and Womble JN. 1997. Abundance and distribution of harbor seals from Icy Bay to Icy Strait, Southeast Alaska during August 1996, with recommendations for a population trend route. Pages 33-56. In Small RJ. Harbor Seal Investigations in Alaska. Alaska Department of Fish and Game, Division of Wildlife Conservation. Anchorage, AK. Annual Report, NOAA Grant NA57FX0367
In August, 1996 we conducted the second series of aerial photographic surveys for harbor seals at haulouts between Icy Bay and Icy Strait along the northeast Gulf of Alaska. A similar survey was conducted in September 1993 by the National Marine Fisheries Service as part of an effort to obtain minimum population estimates throughout Alaska. Our objective, in addition to obtaining a minimum population estimate, was to evaluate this coastline, or a portion of it, for its feasibility and value as a potential route for monitoring trends in harbor seal abundance. The survey area is east of the central/western Gulf of Alaska, where significant declines in harbor seals have been observed, and next to southeast Alaska, where seal numbers appear to be stable or may be increasing. It also includes large tidewater glacial fjords where more than 50% of the seals along the route may aggregate during the late summer molt. We observed a maximum of 4,342 seals on August 19, 1996, about 1,200 more than the maximum observed on a single day during the September 1993 survey, and 1,356 higher than our second highest count. Both the sum of mean and maximum counts were higher during the August 1996 survey than in September 1993. We did not feel that it was appropriate to analyze the 1993 and 1996 for trends, since they were separated by three years and occurred at different times (August vs. September) of the year, although additional survey years should make trend analysis possible. We suggest two possible trend routes in which the terrestrial haulouts could be surveyed within a four-hour period bracketing low tide. The main glacial ice haulouts (Icy and Disenchantment bays) could be surveyed from mid-morning to early evening, since seal numbers do not fluctuate with tide at these haulouts. We acknowledge difficulties in the accuracy and precision of aerial surveys for seals at large glacial ice haulouts, as well as high day to day variance in seal numbers, but we recommend their inclusion in this route (with development of improved methods) because of the large number of seals that rest on glacial ice.
- Type
- Book Chapter
- Authors
- Mathews, Elizabeth; Womble, Jamie
- Units
- GLBA
- Keywords
- Coastal/Marine Systems, Glacier Bay, Gulf Of Alaska, Harbor Seal, haulout site, Johns Hopkins Inlet, Marine Mammal, population decline (harbor seal), population trends (seal), Tugidak Island