REEF’s Grouper Moon Project


Dr. Christy Pattengill-Semmens (REEF) shares new information on the ongoing Grouper Moon Project, its success, and results that have been published in Proceedings of the National Academy of Sciences on the population changes of critically endangered Nassau Grouper in the Cayman Islands.

We are thrilled to share an exciting update from the Grouper Moon Project. After nearly two decades of research and monitoring efforts, the Grouper Moon team has just published some of our key results in the prestigious journal Proceedings of the National Academy of Sciences. The journal, and the academic community, have dubbed the program a rare conservation success story for the critically endangered Nassau Grouper.

For the paper, researchers used tagging and video survey data, collected by our team over the last 15 years at spawning aggregations in the Cayman Islands, to estimate changes in the number of critically endangered Nassau Grouper. In both Little Cayman and Cayman Brac, Nassau Grouper aggregations have more than tripled in response to adaptive management by the Cayman Islands government. On Little Cayman, the aggregating population grew from around 1,200 fish in 2009 to over 7,000 in 2018. This study is the first to show sustained recovery of Nassau Grouper populations following fisheries-induced collapse.

REEF initiated the Grouper in collaboration with the Cayman Islands Department of Environment, and it remains one of our flagship programs. We work in partnership with scientists from Scripps Institution of Oceanography at UC San Diego and Oregon State University. The project is the Caribbean’s oldest continuous grouper spawning aggregation research program, and represents one of the most advanced, multi-faceted tropical fisheries research programs in the world.

As a direct result of data collected by the Grouper Moon Project, in 2016, the Cayman government passed sweeping, science-based protections, banning all fishing of Nassau Grouper during the winter spawning season along with limits on the number and size of fish that can be kept in other parts of the year.

You can read the full scientific study here. A full citation is also included below.

On behalf of our entire Grouper Moon team, I look forward to continuing our important work on spawning aggregations in the Cayman Islands and beyond. Thank you to all who have made financial contributions to REEF that ensure we can continue our important work. In addition to support from our members, REEF’s work as part of the Grouper Moon Project has benefited from financial support by the Lenfest Ocean Program and Disney Conservation Fund. Peter Hillenbrand, Southern Cross Club, and Little Cayman Beach Resort/Reef Divers have all provided significant support for our field operations.

For more information, visit And be sure to check out the PBS Changing Seas documentary filmed a few years ago about our work in the Cayman Islands.


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