Abstract

The precipitous decline in mass spawning aggregations of Caribbean grouper and snapper species has been well documented. One-quarter to one-balf of the known Caribbean aggregation sites are now inactive due to the ease with which aggregating species are caught. Historically, five spawning locations have been documented in the Cáyman Islands. Today, three of these sites are dormant or commercially extinct. In January 2002, an expedition was led by the Reef Environmental Education Foundation (REEF) to Little Cayman Island to document a recently discovered spawning aggregation of Nassau grouper (Epinephelus striatus) on the island's west end. A team of divers conducted visual and video surveys on the aggregation site and on near by reefs for ten days surrounding the MI moon; Size and abundance estimates, colorphase, and courtship and spawning behaviorweredocumented. The Nassau grouper at the aggregationsite shifted ñom mostly white belly phase early in the aggregation cycle to predominately dark phase in the middle of the cycle to mostly bicolor phaseat the end. Toward the middle of the aggregation cycle the number of animáis reached a maximum of approximately 5,200 fish. Courtship behaviors were documented each night and spawning was witnessed on four nights beginning five days after the full moon. Courtship coloration and behavior were documented in ten additional fish species. Five of these species were seen spawning. Hook and line fishing occurred daily on the aggregation. The Cayman Islands Department of the Environment reporteda total catch of 1,934 Nassau grouper during the 10-day project, with an average landed size of 61.9 cm and a female to male sex ratio of 1:1.6 for alllanded fish (39% females).

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