Fisheries Management

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Fisheries Management

Daniel Pauly, University of British Columbia, Vancouver, Canada
Rainer Froese, GEOMAR Helmholtz Center for Ocean Research, Düsternbrooker, Kiel, Germany

Published online: September 2014

DOI: 10.1002/9780470015902.a0003252.pub3

Full Article on Wiley Online Library

Abstract
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Abstract

Fisheries management is the set of science‐based procedures used by government institutions to regulate fishers' access to fisheries resources; this involves temporal and spatial restrictions on the deployment of fishing gear, restrictions on features of these gear and constraints on the species and size composition of the catch, and its overall magnitude. The traditional goal of fisheries management was to achieve maximum sustainable yields. Maximum economic yields are obtained with slightly lower catches from larger fish stocks. Modern fisheries management aims for minimising the impact of fishing on the ecosystem and considers trophic interactions when determining catch levels. A new challenge is the assessment and management of data‐limited fish stocks, which constitute about three‐fourth of the exploited stocks.

Key Concepts:

Fish stocks must be maintained above levels that allow them to produce the maximum sustainable yield.
Mortality caused by fishing may not exceed the rate of mortality from natural causes such as predation, diseases or old age.
The size at first capture must be chosen such that fish can realise their potential for growth and reproduction.
Species with important ecosystem functions, such as forage fish, must be fished less.
Government subsidies to fisheries, by reducing the cost of fishing, allows fishing to continue even when fish stocks are depleted; reducing subsides to fisheries thus contributes to fishery sustainability.
Aquaculture can contribute to the global fish supply, but not when carnivorous fish are farmed, as they consume more fish than they produce.

Keywords: trophic levels; fish farming; quotas; ecosystem management; recruitment; growth; mortality; marine reserves

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	Figure 1. The four factors thought to matter in classical fish population dynamics. Note that, in this framework, the sole link of a given population to the other populations of fish, and to the ecosystem in general, is its natural mortality (M). Food consumption, required for growth (as per eqn ) and reproduction, required for recruitment, are usually not considered explicitly. Adapted from Russel ().
	Figure 2. Yield‐per‐recruit isopleth diagram for a southeast Asian red snapper, generated using eqn for different values of fishing mortality (F) and mean age at first capture (t_c), implying different body size and hence mesh sizes. Most fisheries tend to use meshes that are too small, and fishing mortalities that are too high, for the fish to be able to realise their growth potential (here approximately 300 g per recruit). Hence Y/R analysis often leads to the result, counterintuitive at first glance, that yield (Y) can be increased, whatever the number of recruits (R), by reducing fishing effort and increasing mesh sizes.
	Figure 3. Schematic representation of the key economic factors affecting fisheries. (a) Basic model, in which fishing costs are assumed to be proportional to fishing effort (f), and gross returns proportional to catches (parabola). (b) During the typical development of a new fishery, f will increase past maximum economic yield (MEY) at f₁ (where the economic rent, i.e. the difference between total costs and gross returns, is highest), and past MSY (at f₂), until the equilibrium point (EP, at f₃), where costs and returns are equal, that is, where the economic rent is completely dissipated. In this situation, subsidies, by reducing costs, increase the level of effort at which EP occurs, and thus decrease catches. (c) Price increases, by increasing gross returns, increase the level of effort at which the rent will be dissipated (i.e. from f₃ to f₄), and hence foster overfishing, just as subsidies do. (d) In open access small‐scale fisheries, labour is a major cost factor; when its value tends towards zero (as occurs when there is a large excess of rural labour or if fishing is a part‐time job), resources may become severely depleted.