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Gray whale carcasses in the Eastern Chukchi Sea, 2009–2019
Amy Willoughby, Raphaela Stimmelmayr, Amelia Brower, Janet Clarke, Megan Ferguson
International Whaling Commission
2020
SC/68B/IST/02
Imagery and sighting data on gray whale (Eschrichtius robustus) carcasses from over a decade of aerial surveys in the eastern Chukchi Sea provide insight into the causes of mortality on the species’ northern summer feeding grounds. The Aerial Surveys of Arctic Marine Mammals (ASAMM) project surveys large areas of Eastern North Pacific gray whale summer and autumn habitat and offers a long time series of consistent information on floating and beach-cast gray whale carcasses detected during standardized line-transect surveys. A total of 60 gray whale carcasses were documented July–October, from 2009 to 2019. Carcass sighting rates varied by month and year. Thirty (50%) carcasses were found floating and 30 (50%) were beach-cast. Carcasses were distributed across the study area from 67.5°N to 71.9°N and 155.5°W to 168.9°W. Highest percentage of carcasses were observed in 2012 (22%), followed by 2019 (13%), and 2014 and 2016 (12% each year). The highest number of gray whale carcass sightings occurred in August with the highest gray whale carcass sighting rate occurring in September. Images were obtained for 56 (93%) gray whale carcasses. The majority (n = 41, 68%) of photographed gray whale carcasses had injuries consistent with killer whale predation, and were photo-documented every year except 2010 and 2011.
