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We apply the Bayesian synthesis framework (Givens, 1993; Raftery, Givens and Zeh, 1995) to the BALEEN II population dynamics model (de la Mare and Cooke, 1993) to assess the Bering-Chukchi-Beaufort Seas stock of bowhead whales, using the best and most recent evidence about the species. Unlike methods used in previous bowhead assessments, the Bayesian synthesis method takes full account of the evidence and uncertainty about bowhead life history, abundance and age distribution. This paper describes the scienti c evidence about model inputs and outputs which, when combined with the evidence inherent in the model, provides the basis for inference.

The application of the Bayesian synthesis framework was very successful in reducing uncertainty about quantities of interest; for example, the variance of the estimated annual rate of population increase was reduced by 86%. The recent annual rate of population increase is likely to be in the lower half of the con dence interval computed by Zeh, George and Suydam (1995), but it is almost certainly positive. The analysis described in detail in this paper produced a post-model distribution of replacement yield with its 5% point at 54; two replicate runs obtained values of 56 and 60, respectively, for this percentile. Alternative distributions for model inputs and outputs that we considered gave 5% points ranging from 45 to 68.