Abstract

Spatial differences in phytoplankton biomass and quality caused variation in the larval life-span of queen conch, Strombus gigas. Conch larvae were grown in the laboratory on three assemblages of phytoplankton: 1) seawater from the Great Bahama Bank, 2) seawater from the Exuma Sound shelf, and 3) an algal mixture of cultured Caicos Isochrysis and Chaetoceros gracilis. Larvae in a field mesocosm system were also fed a continuous supply of natural phytoplankton from Bahamian Bank water. In the mesocosm system larvae acheived metamorphic competence in only 13 days. In the laboratory, larvae in the Bank and cultured algal treatments acheived competence in 20 days, but none in the shelf water ever became competent. Individual variation within a cohort occurred in all treatments, with the largest larvae in each treatment approximately twice the size of the smallest. The results suggest that duration of larval life-span for conch larvae could range from 13 to 83 days, if growth was linear. The magnitude of this range means that larvae have the potential to metamorphose in local waters or be transported between countries in the Caribbean. To understand larval recruitment, both larval development and transport processes need to be considered.

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