Multicriterion Decision Merging: Competitive Development of an Aboriginal Whaling Management Procedure
Givens, Geof H., Journal of the American Statistical Association
International Whaling Commission management of aboriginal subsistence whaling will eventually use an aboriginal whaling management procedure (AWMP) chosen from a collection of candidate procedures after grueling simulation testing. An AWMP is a fully automatic algorithm designed to operate on the results of an assessment (i.e., a statistical estimation problem relying on sparse series of whale abundance data) to produce a catch limit in each year of real or simulated management. An AWMP should, as much as possible, meet the conflicting objectives of low population risk, high satisfaction of needed catch, and high rate of population recovery. The choice of the best procedure falls naturally in the multicriterion decision making framework, because one of several candidates must be chosen on the basis of high-dimensional simulated performance summaries over a wide range of assumptions about whales and whaling. However, standard multicriterion decision making methods are impractical and unsatisfying for this prob lem. A method is developed to merge competing procedures into a new procedure that is an admissible Bayes rule. The approach is constructive rather than selective, meaning that it is not intended to produce an automatic winner, but rather a promising new candidate. This merging approach allows the best performance aspects of competing procedures to be combined. Ideally, and in examples shown, the newly constructed procedure outperforms all previous candidates. The approach also permits tuning of a single procedure to enhance performance or to more closely reflect design goals, without a simulation-intensive search over the tuning parameter space. These methods are generalizable to a larger class of decision problems.
KEY WORDS: Bayesian decision theory; Bayes rule; Wildlife population management.
1.1 The International Whaling Commission and Whaling Management
The International Whaling Commission (IWC) is widely recognized as having the authority to establish policy regarding management of cetaceans through the International Convention for the Regulation of Whaling, 1946 (IWC 1995b). The IWC provides member nations with whale harvest quotas for two whaling regimes: commercial and aboriginal subsistence. In 1994 the IWC adopted its "Revised Management Procedure" for commercial whaling, a complex algorithm to establish commercial catch limits in certain areas under certain conditions, given available data on whale stock abundances (TWC 1995a). However, due to various political and implementation disagreements, the IWC has not yet put this procedure into practice; thus no commercial catches have since been allowed. This management procedure was the product of nearly a decade of scientific work, statistical analyses, and simulation evaluation. In the final years of this work, IWC scientists were faced with a decision to choose one of several competing algorithms on th e basis of vast simulation results, diverse and compet ing objectives, and considerable uncertainty about the status and dynamics of whale stocks. Although such a decision seems well suited for a formal statistical decision making approach, IWC scientists relied on less formal collective judgment.
Now the IWC has turned its focus to the development of a management procedure for aboriginal subsistence whaling. Unlike commercial whaling, aboriginal whaling is currently practiced under IWC direction by several aboriginal cultures including Alaskan Eskimos, whom the IWC has provided with an annual quota of about 56 bowhead whales caught (IWC 1998a) from a stock believed to number about 8,200 (Raftery and Zeh 1998). The sense of "aboriginal" here is determined on a case-by-case basis by the IWC, but generally such hunts are conducted by less modern communities of ethnically distinct people for whom whales are an important past or present source of food and whaling plays a major role in the communal sense of cultural identity. …