Abstract

We examined the spatial and temporal distribution of larvae of the hawk wing conch (Strombus raninus), by conducting plankton samples in four sites in the Florida Keys from April 2000 to June 2002. Larvae were collected using a conical plankton net (0.50 m diameter and 202 im mesh). At each site, duplicate 15 minutes surface plankton tows were made. Two stations were sampled at each site: one was over the back reef: (approximate 3 m water depth) and the other was approximate 1.5 km offshore (approximate 35 m water depth). In the laboratory,samples were sorted for S. raninus, larvae were counted, measured and classified as early (<500 im, mid (500-900 im) and late-stage (>900 im). A total of 305 larvae were collected during the sampled period. With exception of Molasses Reef, there were always more larvae offshore than nearshore. Looe Key had the highest percentage of larvae (58%), followed by Sombrero Reef (20%), Molasses Reef (11.5%) and Sand Key (10.5%). Late-stage larvae represented the 99.34%, whereas mid-stage represented 0.66%. No early stage larvae were found. Even when there was not a definite pattern, a higher larvae percentage occurred between April and August, with a highest percentage in April 2000 (29.4%), in 2001, the largest number of larvae was found in August (18.6%), whereas in 2002 the highest number occurred in May (72%). Based upon the larvae size, two recruitment periods could be possible for the species, one in May and another in September. The lack of early larvae stages may indicate low local larval production. Furthermore, the large numbers of latest age larvae suggest that S. raninus larvae might originate in remote locations. Further research should examine these hypotheses.

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