California Sea Grant College Program

Resource scientists have recently shown virtually unqualified support for managing fisheries with marine reserves, signifying a new resource management paradigm that recognizes the importance of spatial processes in both untouched and exploited systems. Biologists promoting reserves have based such support on simplifying assumptions about harvester behavior. This thesis shows that these naive assumptions about the spatial distribution of fishing effort before and after reserve creation severely bias predicted outcomes, generally overstating the beneficial effects of reserves.

This thesis presents a fully integrated, spatial bioeconomic model of the northern California red sea urchin fishery. The model is the first attempt to marry a spatially explicit metapopulation model of a fishery with an empirical economic model of harvester behavior. The biological model is calibrated with parameters representing best available knowledge of natality, growth, mortality, and· oceanographic dispersal mechanisms. The model of spatial behavior is estimated using a large panel data set of urchin harvester decisions, which are recorded in logbooks and on landings tickets.

The economic model tracks repeated decisions that take place on different time and spatial scales. Harvesters make daily decisions about whether to fish and where to fish, conditioned on home ports. On longer time scales, harvesters select a home port, choose between northern and southern California regions, and decide whether to drop out of the fishery. Combining a Random Utility Model with Seemingly Unrelated Regressions, the model predicts the aggregate supply response of fishing effort and the spatial allocation of effort as a function of relative economic payoffs. The economic model is integrated with the biological model to endogenize effort, harvest, biomass levels, and reproductive performance of the population.

The integrated model is used to explore the efficacy of marine reserve formation under realistic assumptions about the determinants of total effort and its spatial distribution. Contrary to the dominant biological modeling conclusions based on naive assumptions, realistic behavioral assumptions lead mostly to pessimistic conclusions about the potential of marine reserves. The thesis results ultimately cast doubt on many of the arguments made by those who advocate closures to enhance fisheries.