Volume 57

Utilization of GIS Mapping in the Measurement of the Spatial Distribution of Queen Conch (Strombus gigas) in Puerto Rico

Marshak, A.R.; Appeldoorn, R.S.; Jiménez, N.
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Date: November, 2004

Pages: 31-48

Event: Proceedings of the Fifty Seventh Annual Gulf and Caribbean Fisheries Institute

City: St. Petersburg, Florida

Country: USA


Measurement of the spatial distribution of queen conch (Strombus gigas) through fisheries-independent underwater surveys was carried out along the west coast of Puerto Rico during 2001 - 2002. Sixty transects were performed from which densities per depth, age class, and habitat were calculated. Transects from this survey were plotted within a Geographic Information System (GIS) in which areas of habitat surveyed were calculated, and exact conch locations along the west coast were estimated. The highest densities of juveniles (26.101 - 27.391 conch/ha) and adults (9.667 – 10.145 conch/ha) were found within shallow seagrass beds. Densities of older conch, although low in value (0.822 – 0.885 conch/ha), were highest within Syringodium habitats. Juveniles were the most frequently encountered conch stage (59.7%; n = 89).\Spatial analyses of this survey data, and of newly plotted data from previously published stock surveys, were performed in order to evaluate the distribution of the Puerto Rican queen conch population at various scales. These analyses revealed that two distinct large groups of individuals surveyed could be identified along the western insular shelf, both of which contained smaller sized juveniles, but varied in depth, habitat, and geographic location. As no significant relation was found between conch size and depth, it is suggested that conch are settling and aggregating into both shallow seagrass and deep algal sand habitats, but higher proportions and densities may be found within shallower seagrasses.

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