Abundance and distribution of finless porpoises in Ise Bay and Mikawa Bay, central Japan

Abstract

We carried out aerial surveys to obtain information on the distribution and abundance of the finless porpoises Neophocaena asiaeorientalis in Ise Bay and Mikawa Bay, central Japan. We flew seven times in 2002, 2003 and 2014. Transects were set in an east–west direction. We covered 90 transects (1,869 km in total length) in 2002, 60 transects (1,244 km) in 2003 and 26 transects (614.4 km) in 2014. In 2002, a total of 225 individuals were seen along those transects. Porpoise abundance was estimated at 2,776 individuals (CV=24.9%) with the density of 1.09 individuals・km^-2. In 2003, a total of 216 individuals were seen. Abundance was estimated at 3,176 individuals (CV=19.7%) with the density of 1.25 individuals・km^-2. In 2014, a total of 178 individuals were seen. Abundance was estimated at 3,920 individuals (CV=21.9%) with the density of 1.41 individuals・km^-2. No significant differences were detected in abundance among the three years.