MODELING THE POTENTIAL OF FISHERY RESERVES FOR MANAGING PACIFIC CORAL-REEF FISHES

The potential use of marine fishery reserves (MFRs) for managing fishe ries on tropical Pacific coral reefs was assessed with an extension of the Beverton-Holt model. The effects of year-round fishery closures o n harvests in adjacent, exploited areas were evaluated. Potential chan ges in spawning stock biomass per recruit (SSB/R) and yield per recrui t (Y/R), when varying fractions of exploitable reef area were closed t o fishing, were estimated from published data, approximated natural an d fishing mortality rates, size- and maturity-at-age distributions, an d ''transfer'' (emigration and immigration) rates. For select cases, f undamental transfer rates were adjusted for possible density-dependent emigration from closed areas as relative densities decreased in surro unding non-closed areas because of continued fishing. Three hypothetic al ''fish types'' were constructed, bracketing the likely extremes in fundamental transfer rates and related life-history parameters of Paci fic coral reef fishes: a small-bodied, fast-growing and short-lived, s trongly philopatric species of damselfish was contrasted with a large- bodied, relatively slow-growing, long-lived, vagile species of jack. A ''surgeonfish'' type was used to represent intermediate parameter val ues. Simulations corroborate previous observations that MFRs contribut e little, if anything, towards increasing Y/R. Results for the highly vagile jack confirm that rapid transfer rates will negate potential ga ins in SSB/R resulting from closures. At the opposite extreme, small r eef philopatriots like damselfishes would almost never be harvested, b ecause of negligible transfer rates, unless the MFR was periodically o pened to fishing. The simulations suggest that the SSB/R of the surgeo nfish type is the most likely to benefit from MFRs, because moderate v agility allows biomass to accumulate within the closure despite harves ting in the non-closed area. Results further suggest that growth rate, fishing effort in the non-closed (open) area, natural mortality, and maturity and harvesting schedules importantly influence the potential of MFRs to augment SSB when transfer rates are low to moderate.