Notes from the Field – 2009 REEF Grouper Moon Project

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Grouper Moon Project researchers and volunteers documented Nassau grouper spawning on all three Cayman Islands in 2009. This spawning release image was taken on the Little Cayman aggregation. Photo by Brice Semmens.
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Thousands of Nassau grouper aggregated to spawn on the west end of Little Cayman Island following the full moon in February. Photo by Phil Bush.
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The Cayman Brac team aboard the Glen Ellen.
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Grouper Moon researchers take video with lasers of individual Nassau grouper on the aggregation. The images are later analyzed to determine the size distribution of the aggregation.
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The Grand Cayman team happy after finding aggregating grouper.
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Dr. Semmens presents findings from the project to over 75 Little Cayman residents and visitors.
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Over 1,000 Nassau grouper were found on Cayman Brac, an area that was previously thought to only have a small, remnant spawning aggregation. Photo by Phil Bush.
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The path of the current drifter that was released at the Cayman Brac aggregation site on the night of spawning (19 days at sea). The current pattern is similar to that seen with drifters released on Little Cayman. Jamaica is in the southeast corner.

Since 2001, REEF has led the Grouper Moon Project, a multi-faceted, collaborative research effort in the Cayman Islands aimed at better understanding Nassau grouper reproduction and the role that marine reserves can play in the long-term protection of this endangered species. The 2009 spawning season was the most ambitious to date for the project. For the first time, we had teams of researchers and volunteers stationed on each of the three Cayman Islands--Grand Cayman, Cayman Brac, and Little Cayman. The field season was certainly a success; among many interesting results and accomplishments, our most exciting find was that the teams on all three islands witnessed Nassau grouper spawning on the same night (Valentine’s Day, of all days! – which happened to be 5 nights after the full moon).

In 2003 the Cayman Island Marine Conservation Board instituted an 8-year fishing ban on Nassau grouper at all historically known aggregation sites in the Cayman Islands. This followed the discovery by fisherman of 7,000 aggregating Nassau grouper on the west end of Little Cayman in 2001 and the subsequent harvest of 4,000 of those fish over two spawning seasons. At the time, all other known Nassau grouper aggregations in the Cayman Islands had become inactive due to over-harvest. Thanks to a three-year grant awarded in 2008 by the Lenfest Ocean Program of the Pew Charitable Trusts, REEF is conducting research through the Grouper Moon Project to evaluate the current status of the Cayman Islands spawning aggregations and the effect of these harvest protections -- “The reproductive biology of remnant Nassau grouper stocks: implications for Cayman Islands Marine Protected Area (MPA) management”.

The broad goals for the 2009 spawning season were to continue monitoring recovery in the large spawning aggregation on Little Cayman, and to expand research into the fate of remnant spawning aggregations on Cayman Brac and Grand Cayman; aggregations on both of these islands were fished to exhaustion in the recent past. In addition to the island specific objectives, the Grouper Moon research program expanded satellite drifter work this season. These drifters, which track current patterns associated with the body of water the grouper eggs were spawned in, will continue to report positions for 45 days after spawning; this length of time is the approximate larval duration for Nassau grouper. REEF also continued education and outreach efforts through public talks about spawning aggregations and the Grouper Moon research. Talks were held at the Little Cayman National Trust and Dive Tech/Cobalt Coast Resort.

2009 Aggregation Season Results Summary

The Little Cayman team continued the long-term monitoring of this aggregation, which includes counting the number of fish that show up, estimating the size of the fish, and recording the timing and amount of spawning observed. The Cayman Brac team’s goal was to document whether or not aggregating Nassau grouper were spawning-- evidence of spawning would refute the theory that Nassau grouper fail to recover once overfished because fish on small aggregations no longer release gametes. In the 2008 spawning season, the Grouper Moon research team discovered the location of an aggregation of Nassau grouper on Cayman Brac. This year, armed with this information, REEF and CIDOE researchers spent the full 2009 spawning season observing, videoing and documenting the Cayman Brac spawning aggregation. In addition, the team was able to accomplish the primary goal of this season’s work on the island—team members both observed and videoed spawning. Objectives for the Grand Cayman team were similar, except that they first had the task of discovering where Nassau grouper on that island go (if anywhere) during the spawning season. Using the acoutic tag pinger signal of just ONE Nassau grouper (of 6 total individuals tagged on Grand Cayman in 2008), divers confirmed the presence of aggregating grouper near the historic East End aggregation site and a dusk dive on February 14th yielded this season’s biggest accomplishment– team members witnessed Nassau grouper spawning on Grand Cayman!

The findings stemming from this work are unquestionably novel, and are certainly good news —protections on aggregation sites that have been fished to exhaustion will protect those few individuals that remain, and will protect stocks of fishes that are contributing to the next generation of this endangered reef fish. Put simply, our research demonstrates that overfished aggregations are down, but not out.

Why Does This Matter?

Nassau grouper are not just icons of the Caribbean; they are a social and ecological cornerstone of the region’s coral reefs. Historically, Nassau grouper represented one of the region’s most economically important fisheries. Unfortunately, due to intense harvest on spawning aggregations, their populations have dwindled to a fraction of their historic numbers. The species became the first Caribbean reef fish to be listed as endangered by the International Union for the Conservation of Nature (IUCN) and the species is candidate listed under the US Endangered Species Act. The precipitous decline in mass spawning aggregations of Caribbean grouper species has been well documented. The majority of known Caribbean aggregation sites are now inactive due to the ease with which aggregating species are caught. And those that are still active contain significantly fewer fish than the 10s of thousands that historically gathered at these special places.

As part of our work on the Grouper Moon Project, REEF will continue to develop a comprehensive assessment of the status of the Cayman Island’s Nassau grouper spawning population as a guide for future Nassau grouper restoration and conservation policy.

Collaborators and Supporters Who Make This Project Possible

REEF would like to thank our collaborators at the Cayman Islands Department of the Environment, specifically Phil Bush, Bradley Johnson, Croy McCoy, James Gibb, Tim Austin, Gina Ebanks-Pietre, Chris Dixon, Keith Neale, Delwin McLaughlin and Robert Walton, as well as Drs. Scott and Selina Heppell from Oregon State University. REEF Volunteers have always been at the core of our Grouper Moon field work and 2009 was no exception – heartfelt thanks to Judie Clee, Thor Dunmire, Tracey Griffin, Doug Harder, Brenda Hitt, Denise Mizell and Sheryl Shea. The Grouper Moon Project has continued through the years empowered by the first year’s success and the passion of early project leader Leslie Whaylen Clift. Assistance from OSU graduate students, Stephanie Kraft and Heather Reiff, is much appreciated. Principal financial support is from the Lenfest Ocean Program of the Pew Charitable Trusts and the CIDOE. Additional funding is from Mr. Wayne Panton, Mr. Dan Scott, Clive and Stella Wood, Franklin and Cassandra Neal, and hundreds of REEF members. Continued in-kind logistical support from island businesses and residents, including the Little Cayman Beach Resort/Reef Divers, the Southern Cross Club and Peter Hillenbrand, is also much appreciated. And finally, our ground-breaking achievements on Cayman Brac would not have been possible without the generous support of Wayne Sullivan, who donated his vessel the Glen Ellen, his time (and patience), his equipment and technical diving expertise, and his crew, Brady Booton and Jules James.

For more information on the project, visit the Grouper Moon Project Webpage. If you would like to support this critical marine conservation research, please donate today through the REEF Website or call REEF HQ at 305-852-0030.

Design by Joanne Kidd, development by Ben Weintraub