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.