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Discontinuous Sustainable Yield: The Exception or the Rule?

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Title Discontinuous Sustainable Yield: The Exception or the Rule?
Names Arnason, Ragnar (creator)
Date Issued 2008 (iso8601)
Abstract The sustainable yield function is a favoured tool in fisheries policy making. Normally, this function is drawn as a continuous curve in effort-yield space. This means that sustainable yield (harvest) is gradually reduced to zero as fishing effort increases. This, however, does not have to be the case. The sustainable yield function may easily be discontinuous in the sense that sustained fishing effort beyond a certain critical level will lead to a discrete fall in yield to zero, i.e., a collapse of the fishery. The corresponding sustainable yield curve then has a gap at the critical fishing effort level. Clearly, the existence of such a gap has major implications for fisheries policy.
It has long been recognized that depensatory biomass growth generally leads to discontinuous sustainable yield curves. What appears to be less well understood is that with fully compensatory biomass growth, fish schooling (patchy distribution of fish over the fishing grounds) generally leads to the same result. Since schooling behaviour is typical of most species of fish ― only the degree of schooling varies ― discontinuous sustainable yield functions tend to be the rule rather than the exception.
This paper considers with these issues. It shows how schooling behaviour leads to discontinuities in the sustainable yield function. It explores the corresponding dynamics of the fish stock and the implications for the risk of stock collapses and fisheries policies designed to avoid them. The paper finally speculates about the impacts of profit maximizing investments by fishing firms on the existence and location of gaps in sustainable yield curves.
Genre Research Paper
Topic Fisheries Economics
Identifier Arnason, Ragnar. 2008. Discontinuous Sustainable Yield: The Exception or the Rule? 11 pages. In: Proceedings of the Fourteenth Biennial Conference of the International Institute of Fisheries Economics & Trade, July 22-25, 2008, Nha Trang, Vietnam: Achieving a Sustainable Future: Managing Aquaculture, Fishing, Trade and Development. Compiled by Ann L. Shriver. International Institute of Fisheries Economics & Trade, Corvallis, Oregon, USA, 2008.

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