Mechanisms by which marine protected areas enhance fisheries benefits in neighboring areas

Ph.D. University of Hawaii at Manoa 2012.Includes bibliographical references.Marine protected areas (MPAs) are tools used for conservation, and have repeatedly shown effectiveness in restoring and protecting fishery stocks inside the MPA. However, MPA benefits to biodiversity and fisheries beyond its boundaries are less clear. Achieving objectives of increasing both fisheries and biodiversity is controversial, particularly for small community-based no-take MPAs (nt-MPAs). This dissertation investigates mechanisms contributing to fisheries benefits from small nt-MPAs in three areas: (1) density-dependent spillover through indirect evidence from density and biomass gradients of fish species and groups (2) density independent--spillover as exhibited by Caranx sexfasciatus life history patterns and (3) the association of C. ignobilis with the nt-MPA as determined by distribution, catch rates and reproduction patterns. Three general gradient patterns resulted: (1) an abrupt decline close to the nt-MPA boundary, (2) an extended and gradual decline from the nt-MPA boundary to fished areas and (4) a decline from the fished area and falling within the nt-MPA. It is estimated that fishery benefits from density-dependent spillover of small no-take MPAs in the Philippines generally occurs at a small scale (10s-100s m). Larger scale benefits appear to come from density-independent spillover as shown in the life history patterns of C. sexfasciatus. Four size classes were identified in different habitat types. Patterns suggest that emigration from the MPA to fished areas is density-independent. Factors driving the habitat shifts include habitat complexity, predator densities, current velocity and the accompanying diet and reproductive shifts. Protection of the existing MPA is limited to C. sexfasciatus intermediate sizes (15--37 cm, SL) and excludes the recruits, younger juveniles and spawning sizes. For C. ignobilis, distribution, densities and fish catch rates patterns suggest a home range center located on the northern traditional fishing grounds beyond the existing Apo Island nt-MPA. The location, size, and mixed use of this MPA make C. ignobilis more vulnerable to exploitation and a less sustainable fishery within the MPA than originally intended. Results suggest that more effective designs of MPAs for fisheries management must take into consideration fish assemblage movements and life history patterns of key coral reef and commercially important fishery species