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On the Economic Optimality of Marine Reserves When Fishing Damages Habitat

Holly V. Moeller, S.M. 2010
Michael Neubert, Advisor

In this thesis, I expand a spatially-explicit bioeconomic fi shery model to include the negative eff ects of fishing eff ort on habitat quality. I consider two forms of eff ortdriven habitat damage: First, fi shing eff ort may directly increase individual mortality rates. Second, fishing eff ort may increase competition between individuals, thereby increasing density-dependent mortality rates. I then optimize e ffort distribution and fish stock density according to three management cases: (1) a sole owner, with jurisdiction over the entire fi shery, who seeks to maximize profi t by optimizing eff ort distribution; (2) a manager with limited control of eff ort and stock distributions, who seeks to maximize tax revenue by setting the length of a single, central reserve and a uniform tax per unit eff ort outside it; and (3) a manager with even more limited enforcement power, who can only set a tax per unit eff ort everywhere in the habitat space. I demonstrate that the economic efficiency of reserves depends upon model parameterization. In particular, reserves are most likely to increase profi t (or tax revenue) when density-dependent fish mortality rates are aff ected. Interestingly, for large habitats that are sufficiently sensitive to density-dependent fi sh mortality e ffects, reserve networks (alternating shed and un shed areas of fi xed periodicity) emerge. These results suggest that spatial forms of management which include marine reserves may enable signi cant economic gains over nonspatial management strategies, in addition to the well-established conservation bene fits provided by closed areas.