Eastern Beaufort Sea beluga (Delphinapterus leucas) population abundance estimate in 2019

Abstract

The Eastern Beaufort Sea (EBS) beluga population abundance was last assessed in July 1992. However, there is new evidence indicating that the EBS beluga distribution extends beyond the area covered by the 1992 survey. Visual and photographic surveys were conducted from July 21 to August 2, 2019 to provide an updated abundance estimate in Canadian waters. The surveys were co-designed with Inuvialuit to include all areas identified as potentially within the range of EBS beluga. Due to poor weather during 2019, survey coverage was incomplete. In particular, large portions of the survey design were not completed despite tag data and other lines of evidence indicating beluga presence. To account for belugas that were missed during the survey because they were underwater, surface and dive data collected concurrently from tagged belugas were used to estimate adjustment factors. An estimated abundance of 38,500 belugas (95% CI = 20,700–71,300) was obtained within the survey area after adjusting for belugas that were submerged or missed by observers. Using this estimate and a recovery factor of 1, the Potential Biological Removal (PBR) was calculated as 588 belugas. Due to low survey coverage, the abundance estimate for the population and associated PBR are negatively biased and should be considered underestimates. A United States National Oceanic and Atmospheric Administration (NOAA) aerial marine mammal survey conducted in August 2019 covered offshore areas but did not cover the entire EBS beluga distribution. Although a beluga abundance estimate can be obtained from this survey, it was not included in this assessment as survey data were still being analysed. The EBS population assessment took a collaborative approach with Inuvialuit that engaged participation in the study design, field implementation/execution and the interpretation of findings for the final assessment.