Grouper Moon: Counting the Last Great Nassau Grouper Gathering

The Grouper Moon Project, a partnership between REEF and the Cayman Islands Department of Environment with scientists from Scripps Institution of Oceanography and Oregon State University, has monitored the Little Cayman spawning aggregation since 2002. Its findings drove sweeping science-based legal protections for Nassau grouper in the Cayman Islands in August 2016, and a 2020 paper in PNAS documented the recovery of the aggregation. REEF describes the site as one of the last great reproductive populations of the species and uses acoustic tagging and AI fish identification to track it. In 2025 many grouper were present but did not aggregate in typical numbers and no spawning was observed, the first such failure in the project's history.