Evaluation of Different Methods for Counting Sea Otters, Enhydra lutris Linnaeus, 1758 (Carnivora: Mustelidae), at the Northwestern Haul-Out Site of Bering Island

The article reviews the known methods for counting sea otters, Enhydra lutris Linnaeus, 1758, of the Commander Islands population that has been steadily declining for the past 15 years. The relationship between the total abundance and the abundance at the northwestern haul-out site on Bering Island is shown: the long-term trend in population size is well identified using a rather large single model haul-out site as an example. The results of different methods for counting sea otters at the haul-out are presented. The use of a thermal imaging camera has been found to increase the efficiency of night-time counts by the drive-through method, especially in snow-free weather, and is independent of light conditions. It is shown that counts at haul-out site can be an alternative to the drive-through method.