Abstract

In 1988 the Turks & Caicos Islands (TCI) government established a number of marine proteeted areas (MPAs) within the Caicos Bank. Such MPAs serve a large range of conservation and management objectives including the protection of both critical habitats and threatened organisms, and the enhancement of fisheries stocks. In the present study the density and the age-structure of the population of Queen conch (Strombus gigas) located within a specially designated marine proteeted area of the Caicos Bank (East Harbour Lobster & Conch Reserve, EHLCR) was compared to the population in the adjacent fished areas. A total of 36 sites were surveyed using scuba divers covering a total area of 21600 m2 and 1087 adult and juvenile conch were identified during the study.\The survey demonstrates that the EHLeR displays a significantly greater density of conch than the fished areas, with a ratio close to 2: 1. The analysis also shows that over the depth range, two to eight meters, density is primarily influenced by habitat type. For both areas, conch were found to be densest in algal plain habitats dominated by benthic algae, while sand plains, associated with sparse to moderate algal or seagrass cover, displayed significantly lower densities of concho Within the EHLCR, mean densities were 2,162 conch/ha in the algal plain and 259 conch/ha in the sand plain, while in the fished area the mean densities were 687 conch/ha in algal plain and 134 conch/ha in the sand plain.\Comparisons of age structure in each habitat show that the population observed in the EHLCR was significantly different from that in the fished area. In the fished areas juveniles were significantly more dense than adults, with the opposite being observed in the protected area. The limitation of the fishing pressure in the protected area resulted in a 355% and 717% increase in adult densities in the sand plain and algal plain habitat, respectively. The powerful effect of MPAs in altering population densities and size/age structure is thus well illustrated with the protection of adult spawning stock within the EHLCR. However the other benefits of MPAs in improving conch fishery productivity in the Tel, emigration of stock into surrounding fished areas (spill-over effeet) and supply of new pelagic larvae (dispersal effeet), rernain untested.

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