A Review of Approaches to Fisheries Management Based on Ecosystem Considerations, With Particular Emphasis on Species Interactions

Executive Summary This report is organized around five interlocking questions regarding ecosystem based approaches to managing aquatic living resources, based on the understanding that management in natural resource contexts is the control of human intervention in ecosystems, and with the general focus of fished stocks that may be both predators and prey for other species in the system. Single-species approaches to management are based in 19th century determinism in which one assumes that stocks can be viewed outside of their role in the ecosystem and that if one knows enough about the vital information concerning the sock, then it is possible to control the trajectory of the stock. The ecosystem-based approach to management recognizes that target stocks sit in food webs, that non-human predators of stocks are competitors with fishing, and that the abiotic environment is part of the milieu in which organisms live and fishing occurs. Ecosystem-based management attempts to bring more of the lessons from ecological sciences (such as thresholds, uncertainty and surprise) into consideration and focuses on both the target stock and non-target species. The ecosystem-based approach has three broad goals: a sustainable yield of products for human consumption and animal foods, maintenance of biodiversity, and protection from the effects of pollution and habitat degradation. In general, three ratchet processes have resulted from single species approaches and have led to problems in fishery management. The first is Odum's ratchet, which is the failure to recognize that harvesting acts as a selective force on ecosystems by culling long-lived and slow growing stocks and individuals in favor of faster growing ones. The second is Pauly's ratchet, which is the tendency for scientists to relate changes in the ecosystem to what things were like at the start of their careers (so that accounts of higher levels of abundance are discounted as anecdotes). The third is Ludwig's ratchet, which is positive feedback between fishing mortality and over-capitalization. Specific problems attributed to single-species approaches to management include stock collapses, shifts in trophic structure, habitat degradation, depletion of non-target species, and bioeconomic conundrums such as the optimality of extinction of a stock. The ecosystem-based approach to management is limited by the requirements of data and the requirements of several levels of administration, and considerable amounts of monitoring. At least a dozen set of principles concerning management of marine ecosystems were published in the last 22 years. Perhaps the most fundamental principle is the …