Abundance estimation of finless porpoises in Japan have been conducted from the line transect method, using vessels or airplanes as the survey platform. The comparison of advantages between the platforms revealed that airplanes are more appropriate for finless porpoise abundance estimation studies. Abundance estimates from airplane sighting surveys conducted in each of main distributional areas of Japanese finless porpoises are reviewed. To evaluate trend in their abundance, estimation studies from airplane sighting surveys should be continued in the same manner.
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