Marine protected areas for spatially structured exploited stocks

GN Tuck, HP Possingham
2000 Marine Ecology Progress Series  
Many harvested manne and terrestnal populations have segments of their range protected in areas free from exploitation. Reasons for areas being protected frorn harvesting include conservation, tounsm, research, protection of breeding grounds, stock recovery, harvest regulation, or habitat that is uneconomical to exploit. In this paper we consider the problem of optirnaily exploitmg a single species local population that is connected by dispersing larvae to an unharvested local population. We
more » ... ine a spatially-explicit population dynamics model and apply dynarnic optirnization techniques to deterrnine policies for harvesting the exploited patch. We then consider how reservation affects yield and spawning stock abundance when compared to policies that have not recognised the spatial structure of the rnetapopulation. Cornpansons of harnest strategies between an exploited rnetapopulation with and without a harvest refuge are also made. Results show that in a 2 local population metapopulation with unidirectional larval transfer, the optimal exploitation of the harvested population should be conducted as if it were independent of the reserved population. Numerical exarnples suggest that relative source populations should be exploited if the objective is to rnaximise spawning stock abundance within a harvested metapopulation that includes a protected local population. However, this strategy can markedly reduce yield over a sink harvested reserve system and may require stnct regulation for conservation goals to be realised. If exchange rates are high, results indicate that spawning stock abundance can be less in a reserve system than in a fully exploited rnetapopulation. In order to maximise economic gain in the reserve system, results indicate that relative sink populations should be harvested Depending on transfer levels, loss in harvest through reservation can be minimal, and is likely to be compensated by the potential environmental and economic benefits of the reserve.
doi:10.3354/meps192089 fatcat:lzex3k3qfzbxref4uvmtzyd6aa