An Exploratory Assessment of the Bering-Chukchi-Beaufort Seas Stock of Bowhead Whales Using a Stochastic Population Dynamics Model

The stochastic population dynamics model used by Aboriginal Whaling Management Procedure developers is revised to correct weaknesses related to uncertainty parameterisation and replacement yield estimation. Two variants of this model, along with the standard determinis-tic version, are used to assess the Bering-Chukchi-Beaufort Seas stock of bowhead whales. The variants diier with respect to the magnitude and complexity of the stochastic variation they introduce into natural mortality and birth/calf survival processes. An allowable catch statistic, Q 0 , is deened for appropriate use with stochastic model assessments. Using the same assessment methods, likelihood and priors as IWC (??International Whaling Commission1999), we nd 5 th percentiles of Q 0 to be 117, 107, and 100 for the deterministic, simpler stochastic, and extreme stochastic models, respectively. Bayes factor results show that there is no evidence suggesting that either stochastic model should be favored over any simpler alternative, and the determin-istic model yielded the best t overall. The Q 0 estimates connrm and strengthen past IWC Scientiic Committee inference that under current bowhead subsistence hunting levels the stock should continue to increase towards stabilisation above its maximum sustainable yield level.