Page 11 - Fishery_Regimes_2005

EMPAFISH Booklet nº 2 Fishery regimes in Atlanto-Mediterranean European MPAs

Introduction

Marine protected areas (MPAs) are areas of the sea where fishing is restricted
or prohibited. They have been proposed throughout the world as an ideal way
to protect marine ecosystems and associated fisheries (Plan Development
Team 1990; Roberts & Polunin 1991; Dugan & Davis 1993; Agardy 1994;
Gerber et al. 2002; Lubchenco et al. 2003) and are seen as key components
in an ecosystem approach to fisheries management (Sutinen & Soboil 2001).
Amongst their chief benefits is their role in conservation of valuable species
and habitats, and the protection of economic resources (Salm et al. 2000).
From a fisheries perspective, MPAs have been advocated as an insurance
against uncertainties related to traditional management measures, which
have in some cases failed to protect stocks against collapse (Pauly et al.
2002).

The effect of fishing protection on the density, size structure and biomass of
fish populations has been thoroughly investigated (see reviews by García-
Charton et al. 2000; McClanahan & Mangi 2000; Russ 2002; Halpern 2003).
In general, fishing reduces population abundance, preferentially removing
larger and older fish, thus changing the size and age structure of exploited
populations (e.g. Jennings et al. 1995) and reducing potential fecundity. So,
the cessation or reduction of fishing may promote an increase of the
recruitment and of abundance as well as the mean size and age of the
individuals of the protected populations.

Increases in the number and biomass of a number of species (Buxton &
Smale 1989) or in the entire fish assemblage of the protected area (Cole et al.
1990; Polunin & Roberts 1993) have been observed in different studies. Most
of these works show that the species more likely to respond to the cessation
of fishing in marine reserves (reserve effect) are large, long-lived predators,
organisms highly vulnerable to fishing and those whose populations are
overexploited (Plan Development Team 1990; Roberts & Polunin 1993;
Bohnsack 1996), meanwhile other species may not be influenced by
protection or may show the opposite response (lower abundance or biomass
in the reserve), presumably due to inter-specific interactions (Pinnegar et al.
2000).

Some studies show that the response time to protection is low and the
positive effects on population density are reached within a period of time of 1
to 3 years (Halpern & Warner 2002).

Furthermore, marine reserves, like fishery reserves, are not closed systems
and can determine a recovery in the productive potential of fishing resources,
inside or in the immediate vicinity of the protected area. On this basis, it is
widely accepted that MPAs offer, as potential advantages to fisheries, a net
exportation of individuals or biomass to adjacent areas, commonly referred to

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