The abundance of harbor seals (Phoca vitulina richardii) has declined in recent decades at several Alaska locations. The causes of these declines are unknown, but there is concern about the status of the populations, especially in the Gulf of Alaska. To assess the status of harbor seals in the Gulf of Alaska, we conducted aerial surveys of seals on their haul‐out sites in August‐September 1996. Many factors influence the propensity of seals to haul out, including tides, weather, time of day, and time of year. Because these “covariates” cannot simultaneously be controlled through survey design, we used a regression model to adjust the counts to an estimate of the number of seals that would have been ashore during a hypothetical survey conducted under ideal conditions for hauling out. The regression, a generalized additive model, not only provided an adjustment for the covariates, but also confirmed the nature and shape of the covariate effects on haul‐out behavior. The number of seals hauled out was greatest at the beginning of the surveys (mid‐August). There was a broad daily peak from about 1100–1400 local solar time. The greatest numbers were hauled out at low tide on terrestrial sites. Tidal state made little difference in the numbers hauled out on glacial ice, where the area available to seals did not fluctuate with the tide. Adjusting the survey counts to the ideal state for each covariate produced an estimate of 30,035 seals, about 1.8 times the total of the unadjusted counts (16,355 seals). To the adjusted count, we applied a correction factor of 1.198 from a separate study of two haul‐out sites elsewhere in Alaska, to produce a total abundance estimate of 35,981 (SE 1,833). This estimate accounts both for the effect of covariates on survey counts and for the proportion of seals that remained in the water even under ideal conditions for hauling out.

We monitored the haul‐out behavior of 68 radio‐tagged harbor seals (Phoca vitulina) during the molt season at two Alaskan haul‐out sites (Grand Island, August‐September 1994; Nanvak Bay, August‐September 2000). For each site, we created a statistical model of the proportion of seals hauled out as a function of date, time of day, tide, and weather covariates. Using these models, we identified the conditions that would result in the greatest proportion of seals hauled out. Although those “ideal conditions” differed between sites, the proportion of seals predicted to be hauled out under those conditions was very similar (81.3% for Grand Island and 85.7% for Nanvak Bay). The similar estimates for both sites suggest that haul‐out proportions under locally ideal conditions may be constant between years and geographic regions, at least during the molt season.

ABSTRACT. Bowhead whales of the Bering-Chukchi-Beaufort Seas stock harvested by Alaskan Eskimos were examined for scars from killer whale and ship-collision injuries. We estimated that the frequency of scars from killer whale attacks ranged from 4.1% to 7.9% (depending on our confidence that the whale was properly examined) while about 1% exhibited scars from ship collisions. The frequency of killer whale scars was considerably lower than for bowhead whales of the Davis Strait stock and for other baleen whales where data are available, and was significantly lower (P < 0.05) for whales < 13 m. Patterns for both types of scars were quite similar to those reported for other cetacean species. Spaces between rake marks were within the range of interdental measurements from four killer whale skulls. The occurrence of attempted killer whale predation and ship strikes inferred from scars has not prevented the BCBS stock from increasing.

Populations of Steller sea lions, northern fur seals, and northern sea otters declined substantially during recent decades in the Bering Sea and Aleutian Islands region, yet the population status of harbor seals has not been assessed adequately. We determined that counts obtained during skiff-based surveys conducted in [1977][1978][1979][1980][1981][1982] represent the earliest estimate of harbor seal abundance throughout the Aleutian Islands. By comparing counts from 106 islands surveyed in 1977-1982 (8,601 seals) with counts from the same islands during a 1999 aerial survey (2,859 seals), we observed a 67% decline over the ∼20-yr period. Regionally, the largest decline of 86% was in the western Aleutians (n = 7 islands), followed by 66% in the central Aleutians (n = 64 islands), and 45% in the eastern Aleutians (n = 35 islands). Harbor seal counts decreased at the majority of islands in each region, the number of islands with >100 seals decreased ∼70%, and the number of islands with no seals counted increased ∼80%, indicating that harbor seal abundance throughout the Aleutian Islands was substantially lower in the late 1990s than in the 1970s and 1980s.Key words: population decline, harbor seal, Phoca vitulina, Aleutian Islands, Gulf of Alaska stock. 845This article is a U.S. government work, and is not subject to copyright in the United States.846 MARINE MAMMAL SCIENCE, VOL. 24, NO. 4, 2008 The population declines of Steller sea lions (Eumetopias jubatus), northern fur seals (Callorhinus ursinus), and northern sea otters (Enhydra lutris kenyoni) in the Bering Sea and Aleutian Islands region during recent decades have prompted substantial efforts to identify the causes of those declines, conserve and manage the species, and interpret marine ecosystem dynamics (Estes et al. 1998, NRC 2003, Springer et al. 2003, Trites and Donnelly 2003, DeMaster et al. 2006, Wade et al. 2007. Less information has been available to determine whether harbor seals (Phoca vitulina) have also declined in the Aleutian Islands region, yet robust estimates of multi-year population trends indicate declines in several relatively small regions in the Gulf of Alaska and Southeast Alaska (Frost et al. 1999, Small et al. 2003, Mathews and Pendleton 2006.Harbor seals were considered common and relatively abundant throughout the Aleutian Archipelago during the 1960s and early 1970s (Pitcher 1985), yet a reliable estimate of abundance is not available for that period or earlier. Harbor seals in the Aleutians have been surveyed on numerous occasions during the past 70 yr: 1930s (Murie 1959), 1956-1957(Mathisen and Lopp 1963), 1960-1965(Kenyon 1960, 1962, Kenyon and Rice 1961, Kenyon and King 1965), 1975-1977(Everitt and Braham 1980(Fiscus et al. 1981), 1986(Brueggeman et al. 1988), and 1992and 2000(Doroff et al. 2003. However, harbor seals were typically not the species for which these surveys were conducted, thus survey effort and protocols varied substantially, and available counts were often incomplete for individual islands as w...

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