This past week marked the 21st year of the Grouper Moon Project, a highly successful conservation science collaboration between REEF and the Cayman Islands Department of Environment (DOE) to study one of the largest and last known spawning aggregations of endangered Nassau Grouper in the Caribbean.

During winter full moons, thousands of Nassau Grouper gather in one location to spawn, and our field research team conducted daily dives on a Nassau Grouper spawning aggregation off the west end of Little Cayman. We documented the number and size of fish gathered at the aggregation by using a variety of methods including stero-video, tag counts, and video pans. Preliminary modeling results suggest that more than 8,000 Nassau Grouper visited this year's aggregation, which is a fourfold increase since 2010!

We also assessed the Nassau Grouper spawning aggregation on Cayman Brac and maintained autonomous monitoring equipment deployed at aggregation locations throughout the Cayman Islands, including acoustic receivers and hydrographic instruments, which are used to document conditions at the sites year-round. By the end of the week, the Nassau Groupers had finished spawning and were observed returning to their home reefs around Little Cayman. Meanwhile, our team continued to visit the aggregation site to monitor Tiger and Yellowfin Grouper spawning, and to collect larvae to be used for various research projects. To connect Caymanian students with the project, our education team also hosted live-from-the-field webchats with local classrooms. These are archived and available for viewing on the REEF YouTube channel.

Since 2002, a team of REEF and DOE researchers, educators, and partners from Scripps Institution of Oceanography and Oregon State University have studied the Nassau Grouper spawning aggregations in the Cayman Islands. Research findings from the Grouper Moon Project have supported science-based legislation passed by the Cayman Islands government in 2016, and serve a blueprint for other conservation efforts in the region. Funding is provided by REEF members, and several foundations. Many volunteers and others have helped in the field through the years. Generous logistical and financial support is provided every year by Caymanian businesses and locals, especially Peter Hillenbrand, Little Cayman Beach Resort, Reef Divers, and Southern Cross Club. We also appreciate continued support from Berkley White and Backscatter, and Marissa Wiganowske and Pegasus Thusters.

Visit to see links to videos and photos, and to read about the scientific publications and legislative actions that have been informed by this work.