Spatial distribution, density, and habitat associations of queen conch Strombus gigas in St. Croix, US Virgin Islands

摘要

Conventional stock assessment methods have been ineffective for determining the status of queen conch throughout the Caribbean, mainly due to a lack of available fishery-independent data. We examined queen conch populations on the northeastern coast of St. Croix, US Virgin Islands, using a 10 m radial survey sampling technique with sample sites stratified by water depth, habitat type, and management regime, encompassing both open and closed fishing areas. We completed 503 radial surveys and located 4773 queen conch, representing an overall density of 302 conch ha(-1). Densities of juvenile and adult queen conch were higher within Buck Island Reef National Monument (BIRNM) boundaries compared to open fishing areas. Densities of juvenile and adult queen conch were highest in habitats characterized as 50-90 and 10-50% patchy seagrass, respectively. Shell length data suggest that the seagrass beds south of Buck Island are functioning as valuable nursery habitat for juvenile conch, and the presence of multiple juvenile cohorts indicates that larval recruitment in the area has been successful in recent years. Comparisons of data from this and previous studies indicate that the queen conch population in St. Croix is potentially stable under the current management approach and that BIRNM is providing the spatial protection required for the population to continue to recover. Given the spatial and temporal patchiness of queen conch distributions, standardized fishery-independent monitoring surveys should be repeated regularly to provide data sufficient to assess stock conditions and the efficacy of management measures.