QUEEN CONCH, STROMBUS-GIGAS, IN FISHED AND UNFISHED LOCATIONS OF THE BAHAMAS - EFFECTS OF A MARINE FISHERY RESERVE ON ADULTS, JUVENILES, AND LARVAL PRODUCTION

Marine fishery reserves (MFR's) have been set aside in coastal areas t hroughout the world with the hope of reversing population decreases co mmonly observed in many marine resources. In this study, a comparison of population structure of the commercially important gastropod Stromb us gigas, queen conch, was made between a fished area and an MFR in th e Exuma Gays, central Bahamas. There were 31 times more adult couch on the shallow (<5 m) Great Bahama Bank in the MFR, and in a survey at 7 depth intervals (to 30 m) on the island shelf in the Exuma Sound, mea n adult density was always higher in the MFR, by as much as 15 times. Shell length and lip-thickness measurements indicated that adults in t he MFR migrate with age from bank nursery sites into deeper sound wate r, whereas those on the bank in the fished area were harvested before reaching water sufficiently deep to protect them from free-diving fish ermen. Although sparsely distributed juveniles in shallow-water (<15 m ) habitats of the sound were the primary source of adults in the fishe d area, large juvenile aggregations on the bank also contributed to th e deep-water adult stock in the MFR. Total larval densities in the MFR were frequently an order of magnitude higher than those found in the fished area, and densities of late-stage larvae were 4 to 17 times hig her. Because the surface current along the Exuma Gays shelf flows to t he northwest, late-stage larvae found inside the reserve must have bee n spawned outside the reserve; thus the high densities of juvenile and adult conch are the result of natural accumulation of larvae in the a rea, as well as the result of protection from fishing. Although the fa te of larvae dispersed from the reserve is uncertain, it is likely tha t high numbers of reproductive stock and larvae in the reserve have a significant positive effect on populations in the northern Exuma Sound . Designs of reserves that consider ontogenetic requirements of the ta rget species and strategic locations for larval production, import, ex port, and metapopulation dynamics will optimize fishery benefits for t he many marine vertebrate and invertebrate species that possess pelagi c larvae.