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ESR prepress abstract   -  DOI:

Incorporating environmental covariates into a Bayesian stock production model for the endangered Cumberland Sound beluga population

Brooke A. Biddlecombe*, Cortney A. Watt

*Corresponding author:

ABSTRACT: The Cumberland Sound (CS) beluga (Delphinapterus leucas) population inhabits Cumberland Sound on eastern Baffin Island, Nunavut, Canada and is listed as Threatened under the Species at Risk Act. Population dynamics of CS beluga whales have been modelled in the past, but the effect of environmental covariates on these models has not previously been considered. An existing Bayesian population model fitted to CS beluga whale aerial survey data from 1990–2017 and harvest data from 1960–2017 was modified to include sea ice concentration (ICE) and sea surface temperature (SST). ICE and SST were extracted for all years from the Cumberland Sound study area in March and August, respectively, and incorporated into the state process component of the state space model. The model resulted in a 2018 population estimate of 1245 (95% CI 564–2715) whales, and an initial population (N1960) estimate of 5147 (95% CI 1667–8779). Determining sustainable harvest by calculating the probability of population decline estimated 30% probability of decline after 10 years with a harvest of ~15 whales annually. Compared to the previous model without environmental covariates, which followed a relatively linear trajectory, our model had more noticeable peaks and troughs in the population trend and wider credible intervals. The model suggested harvest levels be reduced by ~7 individuals for low risk of decline management goals. The novelty of this approach for beluga whales provides an opportunity for further model development via the addition of various other abiotic and biotic variables related to beluga whale ecology.