Preliminary results for a combined assessment of all seven southern hemisphere humpback whale breeding stocks

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University of Cape Town

This paper reports preliminary results from the development of an assessment process that aims to include all seven Southern Hemisphere humpback whale breeding stocks in a single joint assessment, with the purpose of allowing highlatitude historic catches (i.e. catches taken south of 40˚S, where mixing amongst the populations occurs), to be allocated to breeding stocks in proportion to abundance, rather than on set ratios. The approach can be broadened to allow for uncertainties in the placement of the boundaries assumed to link high latitude catches to breeding stocks. Because of the interaction between populations arising from the procedure to allocate high latitude catches amongst breeding stocks, the conventional SIR-based Bayesian approach proved impractical to expand. Instead uniform priors on the various preexploitation level (K) parameters were assumed with the intent to later iteratively adjust these to account for their being informative about the values of the intrinsic growth rate (r) parameters. Initial results (which will need later refinement) are presented purely for the purposes of illustrating the application of the approach.