Abstract
The abundances of six delphinids off the Pacific coast of Japan were estimated using line transect survey data collected in 1985, 1992, 2006, 2007, 2014, and 2015. A multiple covariate distance sampling method was used to estimate a detection function. Because of unsurveyed blocks in 2006, 2007, and 2015, total abundance was estimated only in 1985, 1992, and 2014, when the estimated abundances were for the 3 yr respectively 3,626 (coefficient of variation = 0.74), 2,085 (0.85), and 5,029 (1.24) for rough‐toothed dolphins; 72,762 (0.48), 37,513 (0.54), and 44,529 (0.57) for common bottlenose dolphins; 59,727 (0.46), 60,014 (0.62), and 130,718 (0.43), for pantropical spotted dolphins; 71,983 (0.36), 6,972 (1.03), and 144,163 (0.69) for Risso's dolphins; 38,966 (0.41), 20,507 (0.57), and 31,569 (0.65) for short‐finned pilot whales; and 8,135 (1.23), 5,051 (1.70), and 56,522 (0.56) for melon‐headed whales. To deal with measurement error due to distance and angle, we additionally estimated error‐corrected abundance using data from distance and angle experiments. These new abundance estimates and time series will update 20‐yr‐old estimates and provide a baseline to facilitate dolphin conservation and management around Japan.