The Revised Management Procedure Of The International Whaling Commission: managing the harvest of mixed stocks of baleen whales

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In the early 1980s, the International Whaling Commission established a pause in commercial whaling. One reason cited for this was that scientific uncertainty precluded calculation of safe catch limits using available methods. After eight years of development, in 1994 the IWC adopted (but has not yet implemented) the Revised Management Procedure (RMP) for baleen whales. The RMP is based on the principle of explicitly taking scientific uncertainty into account. The single-stock Catch Limit Algorithm at the core of the RMP has been extensively tested through simulation to ensure robustness to a wide range of uncertainty about: population dynamics, errors in catch and abundance data, etc. However, in real applications, management of multiple stocks is necessary. Here the RMP takes account of uncertainty in knowledge of stock structure and mixing through the spatial spreading of catches. The latter is achieved through evaluating the performance of the RMP in simulated applications to a range of plausible stock structure hypotheses specified to cover the range of uncertainty. A key feature is that catch limits are set for so-called Small Areas, defined as areas known to contain only one stock or, if multiple stocks are present, those stocks mix so that catches can only be taken in proportion to abundance. The greater the uncertainty in stock structure, the more Small Areas are defined.