Abstract

Nassau grouper spawn in large aggregations at specific locations 1-3 times each winter. The fate of the larvae between birth and the time they settle out is virtually unknown, yet the location of the aggregation site itself must be important in determining their fate. In order to investigate the “importance of place” for aggregation-spawning species, during the winter of 2008 we deployed Surface Velocity Profile drifters at the Nassau grouper spawning aggregation site on Little Cayman Island. A single drifter was deployed each night for five nights following the January full moon, then subsequently recovered after 12 hours to determine initial trajectory paths. On the 6th night, when peak spawning was observed, three drifters were deployed simultaneously and tracked for 35 days. The drifters released on the night of spawning showed substantial eddy formation near the aggregation site, in contrast to the largely linear paths taken on nights prior to spawning. This suggests an oceanographic-based “importance of place” for the aggregation site that may result in local recruitment. This would mean that local aggregations of fish are directly responsible for the long-term survival of local populations. We plan to continue our work in 2009. This work will give substantial credence to the need to protect specific locations because they are unique and critical to the long-term survival of the many species that aggregate there, including the important and endangered Nassau grouper.

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