Preliminary mark-recapture abundance estimates of humpback whales on a breeding area in the Mariana Archipelago The Pacific Islands Fisheries Science Center conducted small-boat surveys for endangered Western North Pacific humpback whales off Saipan and neighboring islands in the Mariana Archipelago during the winter months of 2015 to 2019. A total of 42 non-calf whales and 14 calves were observed, and individual resight durations ranged from 1 to 10 d during the 10–18 d survey periods. Preliminary annual mark-recapture abundance estimates of humpback whales within the study area were obtained using photo-identification data collected during the surveys and were adjusted to account for calves. Yearly abundance estimates ranged from 34 (SE, 19; 95% CI, 12 to 92) whales in 2019 to 126 (SE, 44; 95% CI, 65 to 246) whales in 2017, with an average of 61 (SE, 13; 95% CI, 41 to 91) whales across all years. Density estimates were calculated by year for the full study area where surveys were c

Humpback whale Endangered species Monitoring Whale populations Estimates