Beluga whale body condition: evaluating environmental variables on beluga body condition indicators in the Tarium Niryutait MPA, Beaufort Sea

Abstract

The development of indicators as tools for ecosystem monitoring is a key step in the management of marine protected areas (MPAs). This study uses previously developed sex-specific body condition indices, blubber thickness, and girth, to assess temporal changes in body condition from 2000 to 2015 in harvested Eastern Beaufort Sea (EBS) beluga whales (Delphinapterus leucas). Specifically, the goals were to (1) examine seasonal and inter-annual trends of beluga body condition indicators over the harvest season; (2) evaluate associations of body condition indicators across sexes; and (3) test annual means of each body condition index for correlations to regional scale environmental drivers (i.e., the Pacific decadal oscillation (PDO) and sea-ice minimum (SIM) in the Beaufort Sea). Significant seasonal changes in male blubber thickness and female girth indices demonstrated the importance of short-term seasonal drivers. Whilst inter-annual changes in girth and blubber thickness indices revealed longerterm changes, that were correlated between males and females. Only the male girth index had significant relationships with environmental drivers: a negative relationship with the PDO at a zero-year lag, and a negative relationship with the SIM at a two-year lag. The PDO is believed to capture broader environmental changes occurring at wintering habitats and migration routes of the EBS beluga that reveals connectivity between the EBS beluga home range and body condition metrics. While body condition metrics for harvested EBS belugas are regularly collected under a long-running beluga monitoring program, the interpretation and application to MPA monitoring remains difficult. We recommend the continued collection of both girth and blubber thickness measurements along with the inclusion of Inuvialuit Knowledge and observations to strengthen interpretations and inform monitoring of beluga health.