Abstract

In Venezuela, the populations of the queen conch, Strombus gigas, were submitted to very high levels of exploitation which resulted in the national closure of the fishery in 1991. The present study determined the distribution, density, and abundance of the queen conch in the Los Roques Archipelago. A visual sampling, there was assement, conducted by SCUBA divers Swiming transects, was carried out between July and September 1999. It involve a first random samplingcomprising the entire insular plataform and second startified, random sampling in the two blocks (northeast and south-southwest) where, according to the first field sampling there was a greater abundance of queen conch. A total of 45.46 hectares covered during the samplings, at a mean area per transect of 2,859 m2. Individuals were found in 42 and 44 of the 78 and 56 localities visited in each phase of the sampling, respectively. A total of 641 conchs were observed, comprised primarily of adults (60%).\The overall density was estimated as 18.78 conch/ha (S.D.= 44.48), with an approximate abundance of 1,374,640 conchs (C.L. = 640,474 - 2,023,897) for the 73,197 ha of the platform. The density of juveniles and subadults was of 1.76 conch/ha (S.D.= 4.85), with an abundance of 128,827 conchs (C.L. = 49,042 205,684). On the northeast block, the overall density estimated was 34.74 conch/ha (S.D.=77.46) and on the south-southwest block 52.34 conch/ha (S.D.= 92.15), with an abundance of 428,970 conchs (C.L. = 206,706 - 795,952) and 332,097 conchs (C.L. = 138,892 - 555,314) in the northeast and south-southwest areas, respectively. The confidence limits of the abundance estimates were calculated using a Bootstrap technique. The northeast block showed the highest density of young conchs, 7.54 conchs/ha (S.D.= 12.88), representing a zone with potential breeding areas. The highest densities of juvenile (18.31 conchs/ha) were found on seagrass beds, at no more than 10 m depth. Significant populations of adults and older individuals, actively mating, were found on sand plains at depths greater than 16 m

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