restricted access VII.2 Fisheries Management
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VII.2 Fisheries Management Ray Hilborn OUTLINE 1. The history of fisheries and ecological thought 2. The nature of a fishery 3. The biological basis of sustainable harvesting 4. Ecosystem effects and interactions 5. The human ecology of fisheries 6. How fisheries are managed 7. The current state and future of the world’s fisheries Fisheries constitute the most significant example of exploitation of natural ecosystems to produce protein for human consumption. Fisheries are an important part of ecology, both because of their importance for humans and because of the impact fisheries have on almost all oceans, lakes, and rivers. A fishery consists, at a minimum, of an ecosystem and a collection of humans who exploit it. In most cases there is now a third component, a management system. This chapter explores the ecology of the exploited ecosystems and how they interact with the human ecology of exploiters and the managers. GLOSSARY bionomic equilibrium. The balance between fish stock abundance and the fishing fleet that a fishery will evolve to in the absence of regulation by-catch. The unintended catch of a nontarget species in a fishery fish stock. A population of a single species that is geographically distinct enough to be managed separately from other populations of the same species fishery. The interaction between humans and an exploited fish stock maximum sustained yield. The highest long-term average yield that can be obtained from a fish stock on a sustainable basis trophic interaction. Interaction between species in an ecosystem as a result of predation or the consequences of predation unfished or virgin biomass. The average stock size in an unexploited condition 1. THE HISTORY OF FISHERIES AND ECOLOGICAL THOUGHT Regulations to promote the conservation of fisheries originated in Europe in the fourteenth century over concern about Atlantic salmon. Similarly, in North America, where the salmon runs seemed inexhaustible, the need for restrictions on catch was recognized soon after the salmon fishery began to develop. However, the susceptibility of marine fish to overexploitation was recognized much more slowly, and Thomas Huxley (known as Darwin’s bulldog for his advocacy of the theory of evolution) championed the school of thought that the fecundity of fishes was so large that fishing could not have an impact on the abundance of fish in the sea, and ‘‘that the cod fishery, the herring fishery, the pilchard fishery, the mackerel fishery, and probably all the great sea-fisheries, are inexhaustible; that is to say that nothing we do seriously affects the number of fish. And any attempt to regulate these fisheries seems consequently . . . to be useless.’’ Numerous European and North American scientists led the way in providing evidence that fishing not only could affect the abundance of marine fish but could reduce the abundance of certain fish stock so much that their potential yield was reduced. These early scientists also developed the theoretical basis for understanding fisheries production, as elaborated in a later section of this article, and from their work emerged the concept of maximum sustained yield (MSY), the maximum long-term average catch that could be removed from a population on a sustainable basis. By the 1950s the concept of MSY was firmly entrenched in fisheries thinking as an objective of management and as an intrinsic property of most natural populations, and there had developed an elaborate set of methods for calculating it. The simple view of MSY of the 1950s has gradually faded as we have come to recognize the complexity of society’s objectives, the difficulty in estimating the productive potential of natural populations, the natural variability of ecosystems , the interaction between species in ecosystems, and the problems inherent in regulating the exploiters of the resources. At the same time, economists were studying the nature of fisheries and determined that in the absence of regulation, fisheries would evolve toward the ‘‘bionomic equilibrium,’’ in which fishing boats and fleets could just meet their costs but not produce any true profit. So long as a fishery was profitable, more fishermen would enter the fishery and reduce the profit of everyone participating. As a general rule, fisheries in Europe and North America were barely managed until the stocks had been depleted enough that fishermen were economically struggling, and some of the users recognized the need for regulation to reduce fishing effort. The consequence of this was that the natural trajectory of most stocks was to be exploited much harder than MSY and reduced to lower levels, and there...