PARENT SESSION
Oral Session #11: Aquatic Ecology: Conservation, Plankton, Invertebrates.
Presiding: C. Cooper
Monday, August 5. 8:00 AM to 11:30 AM. Palo Verde Room, Radisson.

The effects of marine reserves on yield, abundance, and extinction times: A structured metapopulation model.

Hill, M. Forrest^*,1, Hastings, Alan², Botsford, Louis³, ¹ University of California-Davis, Davis, CA² University of California-Davis, Davis, CA³ University of California-Davis, Davis, CA

ABSTRACT- Marine reserves have been proposed as a remedy for overfishing and for reducing uncertainty in fisheries management. They have the potential to preserve species diversity and ecosystem integrity, but concerns reserves would reduce yields have thwarted their implementation. We developed deterministic and stochastic models for a structured metapopulation to study how dispersal rates, environmental variability and reserve size affect yield, abundance and the mean time to extinction of exploited fish populations. The determinist model predicts the maximum sustainable yield, Y_msy, and equilibrium abundance, &pover;, as a function of reserve size, c, and the dispersal rate between reserve and non-reserve habitat, . We show reserves can produce yields equivalent to traditional fisheries management and there is a maximum reserve size, &cover;, below which the Y_msy declines dramatically. In general, &cover; is an increasing function of , while &pover; is a decreasing function of . The stochastic model estimates extinction times as a function of reserve size and the dispersal rate. It predicts that reserves can significantly reduce the probability of extinction compared to non-reserve fisheries with similar yields. The magnitude of this effect depends on the level of environmental variability and the amount of environmental autocorrelation between reserve and non-reserve regions. Our results show that reserves can increase population sustainability without reducing yield. Determining the optimal reserve size in natural systems, however, will be difficult due to biological and physical uncertainties.

KEY WORDS: marine reserves, metapopulation models, extinction times, yield