The southern sea otter population, which once numbered about 16,000 animals, is hovering around 3,000 today. Kiska and Little Kiska include Pyramid Island; Great Sitkin includes Ulak, Aziak, Tanaklak, Kanu, Asuksak, and Tagadak islands; Atka includes Segchudak, Sadatanak, Amtagis, and Salt islands; Umnak and Samalga include Bogoslof, Vsevidof, Ogchul, Kigul, and Adugak islands. Two or more surveys were conducted in separate years at each of these islands during the 1990s. Frequency distributions of proportional changes in abundance (Nt2/Nt1) of sea otters among islands in the Aleutian archipelago, a-c) All islands surveyed during both years for which ≥20 otters were counted during at least 1 survey and d-f) only for those islands which were at or near K (defined as the population status when growth ceased because of resource limitation) in 1965. Population Trend (-10 to 10) 2 Distribution Trend (-10 to 10) By the early 20th century, northern sea otters were nearly extirpated from Alaska as a result of overharvest (Muto et al. Sea otters in the Aleutian archipelago have declined substantially in number. All of these increases occurred at islands with small otter populations in 1965. Emergent trends, however, become more certain when similar counts are summed over multiple islands. Ballachey B. E. Bodkin J. L. Degange A. R.. Bodkin J. L. Burdin A. M. Ryazanov D. A.. Burnham K. P. Anderson D. R. Laake J. L. Comerci, A. DeGange, S. Kalxdorff, and C. Price were observers during the aerial surveys. The findings point to the importance of otters in the Aleutians, where the marine mammals act not just as predators, but protectors, maintaining biological balance through their voracious appetites. Diverse hypotheses have been advanced to explain the pinniped declines, but their cause (or causes) remains uncertain (National Research Council 1996). Sea otters once also occupied a large range of coastal marine environments near these islands, but in recent years, otter populations have declined in response to their own main predator. Sea otters, … Historically, more than 90 percent of the eagles' food comes from the ocean. The population declined to a uniformly low density in the archipelago, suggesting a common and geographically widespread cause. The Aleutian archipelago extends westward from Unimak Pass to Attu Island (Fig. But against the backdrop of climate change, Dr. Rasher said, the reef’s safety net is gone. Marks D. M. Tinker M. T. Nolan K. Peirce J.. Oxford University Press is a department of the University of Oxford. The sea otter population in Prince William Sound was also hit hard by the Exxon Valdez oil spill , which killed thousands of sea otters … We analyze trends in sea otter abundance by comparing the number of animals counted over time and by computing proportional changes between time periods. Mean encounter rates (otters/km) for the shoreline and transects were compared between 1992 and 2000 surveys. Climate change has greatly contributed to this occurrence and the decline in the sea otter population. The sea otter declines, which appear to differ from their terrestrial counterparts in both pattern and apparent cause, are remarkable because they occurred immediately after abrupt population declines in 3 broadly sympatric species of pinniped (northern fur seals Callhorinus ursinus, Steller sea lion E. jubatus, and harbor seals P. vitulina—. “For their size and how cute they are, they are aggressive eaters.”. The sea otter population decline in the western Aleutian Islands prompted the United States Fish and Wildlife Service to designate this stock as threatened under the United States Endangered Species Act in 2005. Encounter rates of sea otters for each island were obtained by dividing the uncorrected counts by the length of shoreline surveyed (hereafter these measures are referred to as densities). This is arguably the case for all large terrestrial carnivores (Diamond 1984), including various species of wolves, bears, and large cats throughout the world, although in most cases the declines are poorly chronicled. These data chronicle one of the most widespread and precipitous population declines for a mammalian carnivore in recorded history. Behavior. 1). In 2001, the US Fish and Wildlife Service (USFWS) designated the Aleutian Islands population of northern sea otter as a candidate species for listing under the Endangered Species Act (ESA). Hence, the westward extent of the decline appears to be Attu Island. Skiff-based surveys and related studies were supported by the National Science Foundation and the Department of Defense Legacy Program. However, though the protective history of the sea otters looks promising for their future, this nation’s wasteful and lazy attitu… 1) when viewing conditions were good to excellent (Beaufort sea state of 1–2, and >1 km of clear visibility at sea level). Expected distributions were computed from a lognormal density function with a mean of 1 and the observed variance. “There was this incredible diversity,” he said. We arbitrarily restricted this comparison to islands at which ≥20 otters were counted during at least 1 of the surveys, to avoid spurious results. To quantify uncertainty for these estimates, we computed 95% confidence interval (CI) for both predecline abundance and trend lines for decline, then calculated intersection points for both trajectories and confidence limits. Softened by warming and acidifying waters, the coral-like structures have quickly succumbed to the urchins’ tiny teeth, which can annihilate years of fragile algae in a single bite. 1980; T. Evans et al., in litt.). Last month the agency released results of its most recent survey, completed in April, which puts the Aleutian population at 6 000 otters, down from a 1980s estimate of 55 000-100 000. We surveyed the shoreline of each island in its entirety. The latter analysis included all the Rat and Delarof islands, and the Andreanof Islands from Great Sitkin westward (n = 23 islands; Table 1) in which ≥20 otters were counted in at least 1 survey period. = 0.06, P > 0.05 ) Ashland, B. Elmer, Blaesing. And 2 ) the reef ’ s safety net is gone in 1970, Jim Estes his. Be a difficult task, given the probable cause of this decline.. 2 that could be difficult! One of the form Nt = N0ert = 0.06, P > 0.05 ) underway 1992! 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