Andre E. Punt

School of Aquatic and Fishery Sciences, University of Washington, Seattle, WA 98195-5020

Decision rules (or management procedures) have been advocated as a means to implement the precautionary approach to fisheries management. The key features of a decision rule is that it is clearly defined (e.g. includes the data to collect and how regulatory mechanisms are to be based on the analyses of those data) and that it is chosen by means of Monte Carlo simulation to achieve pre-specified management objectives. Decisions rules are currently being applied in Iceland, Namibia, South Africa, New Zealand, Australia, and by the International Whaling Commission, while there are plans to apply them in several other jurisdictions.
The vast bulk of the decision rules in use today are used for the management of fisheries that target single species. In contrast, there is increasing focus on the necessity to consider (and achieve) management objectives that include ecosystem and multispecies considerations. Multispecies interactions can be divided into biological interactions (relating to predation, competition, etc.) and technological interactions (interactions that arise due to the catching process). Development of decision rules to deal with biological and technological interactions is therefore an active research area with obvious management relevance.
Progress on developing decision rules that take biological interactions into account has been slow, primarily because the data required to quantify such interactions (particularly the response of predators to changes in predator and prey abundance) is largely absent. The attempt to manage sealing and the hake fishery off South Africa provides an illustration of this. Depending on the choice of model formulation, large-scale culling of the Cape fur seal may have large or negligible benefits for the hake fishery.
In contrast to the situation regarding biological interactions, decision rules that take account of technological interactions have been developed and are being used. An example of this is the joint anchovy-sardine decision rule developed to manage the pelagic fishery off South Africa. This decision rule makes use, when determining the Total Allowable Catches for sardine and anchovy, of the expected level of by-catch of juvenile sardine when harvesting anchovy.