The Grouper Moon Project is a conservation science partnership between Reef Environmental Education Foundation (REEF) and the Cayman Islands Department of Environment (DoE) with scientists from Scripps Institution of Oceanography at UC San Diego and Oregon State University, aimed at studying Nassau grouper (Epinephelus striatus) - a social and ecological corner stone of Caribbean's coral reefs.


Key Conservation Success and Outputs

January 2020 - New scientific paper from the Grouper Moon team that documents a successful recovery of Nassau Grouper populations in the Cayman Islands. It also highlights the value of collaborative efforts for conservation success. The study, published in Proceedings of the National Academy of Sciences, is available here. Read more here. All publications from the project are listed below.

August 2016 - Grouper Moon findings lead to sweeping science-based legislative protections for Nassau Grouper in the Cayman Islands! Read More Here.

July 2012 - "Changing Seas", an informative PBS documentary featuring the research, conservation efforts, and education program of the Grouper Moon Project. Click here to watch.


Other Resources, Articles, and Videos


What are Nassau Grouper?

Normally solitary and territorial, during the winter full moons grouper travel, sometimes over great distances, and “group” together to spawn. About fifty of these spawning aggregations sites have been recorded in different places throughout the Caribbean. Historically, once discovered, grouper aggregation sites have become synonymous with fisherman aggregation sites. Due to the timing and site fidelity of the spawning aggregations and the ease with which these relative loners can be caught while congregating by the hundreds and thousands to spawn, one-third to one-half of the known Caribbean aggregation sites are now inactive. The Cayman Islands used to be home to five Nassau grouper (Epinephelus striatus) spawning sites. Today, four of these sites are dormant or depleted. But one site, on the west end of Little Cayman Island, is home to one of the last great reproductive populations of this endangered species.





Grouper Moon Project Overview and Research Components

Photo by Paul Humann
In the Winter of 2002, REEF launched a ground breaking expedition to the Cayman Islands - the Grouper Moon Project. The Project’s objectives were to observe the Nassau grouper spawning aggregation off the western tip of Little Cayman, and to develop a protocol for monitoring their numbers and activity at the site. For two weeks, a team of divers from REEF and the Cayman Islands Department of Environment visited the aggregation site and nearby reefs. Since that first year, REEF has coordinated annual efforts to monitor and study the Little Cayman Nassau grouper aggregation. The project has grown in scope to include an ambitious acoustic tagging research project, juvenile habitat and genetics studies, and early results have been published in the scientific literature.


Components of the project include:

Nassau Grouper: A Caribbean Icon, Education Program - In the Fall 2011, REEF and our collaborators started development of an education program that coincides with the Grouper Moon Project. Working with a professional educator, the program includes curricular materials and classroom lessons, as well as "meet the scientist" and "live from the field" sessions. Working in collaboration with classrooms from Cayman Prep and High School, and with funding from the Disney Worldwide Conservation Program, we piloted the program during the aggregation field season in 2012. It has been ongoing since then, and each year several Caymanian schools participate. To view a short clip of one of the underwater live-link session, showing project scientist Dr. Brice Semmens answering qustions from students while underwater, click here. To find out more about this program, visit the Grouper Education Project EduBlog. You can also watch archived underwater Live-Feeds.

Active Acoustic Research to Study the Soundscape - From 2015 to 2107, the Grouper Moon Project collaborated with Scripps Institution of Oceanography researchers, Katherine Wilson and Ana Širović, on the soundscape of the Little Cayman spawning aggregation. As part of this work, our team deployed a hydrophone array at the Nassau Grouper spawning aggregation site with the objectives to 1) localize the sounds produced by aggregating Nassau Grouper to examine the dynamics of the aggregation overnight and during the periods that are not monitored by our Grouper Moon research team, and 2) analyze the soundscape and the characteristics of all the known sounds produced by grouper at this multi-species spawning aggregation to study the sound communication of these fishes. The latter objective included localizing these sounds to measure sound levels and estimate detection and eventually communication ranges for the sounds of these species.

Baby Grouper Adrift! - Satellite Drifter Project - Spawning aggregations are typically located at promontories that feature a confluence of currents and waves. Why there? Using satellite drifters, we studied the passive transport of Nassau Grouper larvae spawned at the protected aggregation sites in the Cayman Islands to better understand the importance of place. The original drifter research was funded by the Disney Worldwide Conservation Program. To visit the 2011 Baby Grouper Adrift! webpage, click here.

Marine Protected Areas and Spawning Aggregations - Starting in 2008, REEF and our collaborators at the Cayman Islands Department of the Environment (CIDOE) and Oregon State University (OSU) greatly expanded the conservation science research being conducted as part of the Grouper Moon Project in the Cayman Islands. The funded research, broadly titled as "The reproductive biology of remnant Nassau grouper stocks: implications for Cayman Islands Marine Protected Area (MPA) management" aims to evaluate the potential for spawning site MPAs to recover Nassau grouper stocks. This research was funded by a grant from the Lenfest Ocean Program at the Pew Charitable Trusts and expanded on the initial findings of the Acoustic Research Project that was started in 2003.

Passive Acoustic Research Project - In 2003 the Cayman Island Marine Conservation Board instituted an 8-year total fishing ban on all known Nassau grouper (Epinephelus striatus) aggregation sites in the Cayman Islands. This project was conducted to provide a clearer understand of how local populations of Nassau grouper use aggregation sites, to evaluate the effect of the no-take status of aggregation sites, and in order to assess the likelihood that the closures are effective. We acoustically tagged Nassau grouper both on and off the Little Cayman west end aggregation site, and monitored movements of the tagged fish over a two year period using an array of passive autonomous hydrophones surrounding the island. This work was funded by the NOAA International Coral Reef Conservation Program. For more information, results, and to watch videos of Nassau grouper movement to and from the aggregation, click here.

Photo by Jim Hellemn


Waterhouse, L, SA Heppell, CV Pattengill-Semmens, C McCoy, P Bush, BC Johnson, BX Semmens. 2020. Recovery of critically endangered Nassau grouper (Epinephelus striatus) in the Cayman Islands following targeted conservation actions. Proceedings of the National Academy of Sciences. Jan 2020, 201917132; DOI: 10.1073/pnas.1917132117. More Details.

Wilson, KC, BX Semmens, CV Pattengill-Semmens, C McCoy, A Širović. 2020. Potential for grouper acoustic competition and partitioning at a multispecies spawning site in Little Cayman, Cayman Islands. Marine Ecology Progress Series, 634: 127-146. doi:10.3354/meps13181. More Details

Wilson, KC, BX Semmens, SR Gittings, CV Pattengill-Semmens and A Širović. 2019. Development and evaluation of a passive acoustic localization method to monitor fish spawning aggregations and measure source levels. OCEANS 2019 MTS/IEEE SEATTLE, Seattle, WA, USA, 2019, pp. 1-7. doi: 10.23919/OCEANS40490.2019.8962663. More Details.

Egerton JP, AF Johnson, L Le Vay, CM McCoy, BX Semmens, SA Heppell, and JR Turner. 2017. Hydroacoustics for the discovery and quantification of Nassau grouper (Epinephelus striatus) spawning aggregations. Coral Reefs. 36 (2): 589-600. More Details.

Bernard, AM, KA Feldheim, R Nemeth, E Kadison, J Blondeau, BX Semmens, MS Shivji. 2016. The ups and downs of coral reef fishes: the genetic characteristics of a formerly severely overfished but currently recovering Nassau grouper fish spawning aggregation. Coral Reefs. 35:273–284 More Details.

Archer, SK, JE Allgeier, BX Semmens, SA Heppell, CV Pattengill-Semmens, AD Rosemond, PG Bush, CM McCoy, BC Johnson, CA Layman. 2014. Hot Moments in Spawning Aggregations: implications for ecosystem-scale nutrient cycling. Coral Reefs. 10.1007/s00338-014-1208-4. More Details.

Jackson, AM, BX Semmens, Y Sadovy de Mitcheson, RS Nemeth, SA Heppell, PG Bush, A Aguilar-Perera, JAB Claydon, MC Calosso, KS Sealey, MT Schärer, G Bernardi. 2014. Population structure and phylogeography in Nassau Grouper (Epinephelus striatus), a mass-aggregating marine fish. PLoS ONE. DOI: 10.1371/journal.pone.0097508. More Details.

Jackson, AM, BX Semmens, and G Bernardi. 2012. Characterization and cross-species amplification of microsatellite markers in Nassau grouper (Epinephelus striatus). Molecular Ecology Resources. 12(5): 972- 974. More Details.

Heppell SA, BX Semmens, SK Archer, CV Pattengill-Semmens, PG Bush, CM McCoy, SS Heppell, BC Johnson. 2012. Documenting recovery of a spawning aggregation through size frequency analysis from underwater laser calipers measurements. Biological Conservation. 155: 119-127. More Details.

Archer SK, SA Heppell, BX Semmens, CV Pattengill-Semmens, PG Bush, CM McCoy, BC Johnson. 2012. Patterns of color phase indicate spawn timing at a Nassau grouper Epinephelus striatus spawning aggregation. Current Zoology. 58 (1): 73-83. More Details.

Semmens BX, PG Bush, S Heppell, B Johnson, C McCoy, CV Pattengil-Semmens, and L Whaylen. 2007. Charting a Course for Nassau Grouper Recovery in the Caribbean: What We’ve Learned and What We Still Need to Know. 60th Gulf and Caribbean Fisheries Institute Meeting Proceedings. More Details.

Whaylen, L., PG Bush, BC Johnson, KE Luke, CMR. McCoy, S Heppell, BX Semmens, and M Boardman. 2006. Aggregation dynamics and lessons learned from five years of monitoring at a Nassau grouper spawning aggregation in Little Cayman. 59th Gulf and Caribbean Fisheries Institute Meeting Proceedings. More Details.

Semmens, BX, KE Luke, PG Bush, CMR McCoy, and BC Johnson. 2006. Isopod infestation of post-spawning Nassau grouper around Little Cayman Island. Journal of Fish Biology 69: 933-937. More Details.

Taylor, JC, DB Eggleston, and PS Rand. 2006. Nassau grouper (Epinephelus striatus) spawning aggregations: hydroacoustic surveys and geostatistical analysis. NOAA Professional Paper. NMFS 5: 18-25. More Details.

Semmens BX, KE Luke, PG Bush, CV Pattengil-Semmens, B Johnson, C McCoy, S Heppell. 2005 Investigating the reproductive migration and spatial ecology of Nassau grouper (Epinephelus striatus) on Little Cayman Island using acoustic tags – An Overview. 58th Gulf and Caribbean Fisheries Institute Meeting Proceedings. More Details.

Whaylen, L, CV Pattengill-Semmens, BX Semmens, PG Bush, and MR Boardman. 2004. Observations of a Nassau Grouper Spawning Aggregation Site In Little Cayman, Including Multi-Species Spawning. Environmental Biology of Fishes. 70: 305-313. More Details.

Yearly Project Summaries

Click here to read annual summaries of the Grouper Moon research.