Grouper Moon Project - Yearly Project Summaries

A collaborative conservation program between REEF and the Cayman Islands Department of the Environment

Yearly Project Summaries

2009 Project |2008 Project |2007 Project |2006 Project | 2005 Project | 2004 Project | 2003 Project | 2002 Results

BACK to the Main Grouper Moon Page

2009 Grouper Moon Project Summary

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.

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!

Read more and see images from 2009 in the REEF-in-Brief article.

2008 Grouper Moon Project Summary

Thanks to a three-year grant from the Lenfest Ocean Program at the Pew Charitable Trusts, REEF and collaborators at the Cayman Islands Department of the Environment (CIDOE) and Oregon State University (OSU) will greatly expand the conservation science research being conducted as part of the Grouper Moon Project in the Cayman Islands. The funded research, entitled "The reproductive biology of remnant Nassau grouper stocks: implications for Cayman Islands Marine Protected Area (MPA) management" will evaluate the potential for spawning site MPAs to recover Nassau grouper stocks. Over the next three years, REEF will continue the ongoing aggregation monitoring and acoustic research that has been conducted on the Little Cayman aggregation since 2002 and expand efforts to Cayman Brac and Grand Cayman, where historical spawning aggregations were fished out during the last ten years. Four primary research questions being asked as part of the Lenfest-funded project are: 1) Do aggregations form in regions that have been fished out? 2) If aggregations form, do the fish ultimately spawn? 3) Do these aggregations form at historic sites or somewhere else? And, 4) Does spawning at these remnant aggregations result in new recruitment? The new research kicked into gear in January with a team of Grouper Moon scientists and REEF volunteers who conducted twelve days of field work in Little Cayman and Cayman Brac. The team visually monitored the Little Cayman aggregation, documenting the largest number of fish since the fishing ban was implemented in 2003. Spectacular mass spawning was documented at dusk seven days after the full moon. Grouper Moon scientists conducted extensive work on Cayman Brac to enable future visual monitoring on the historical aggregation site.  Scientists also initiated an acoustic tagging study that will facilitate a better understanding of the behaviors of Nassau grouper on an island with a limited number of reproductively-aged individuals.Capitalizing on the the increased breadth of research questions being asked as part of the Lenfest Ocean Program grant, the CIDOE is supporting a larval dispersal study that also kicked off this year under the guidance of Dr. Scott Heppell from OSU. Three satellite drifters were deployed at the Little Cayman aggregation site on the night of spawning. The paths will be recorded by ARGOS satellites for 45 days and the resulting data will be used to develop a larval dispersal model in collaboration with researchers from University of Miami.

Check out the 2008 image gallery to see images and video from this year's research as well as to see movement tracks of the satelite drifters.

2007 Grouper Moon Project Summary

A team of Grouper Moon scientists and REEF volunteers conducted annual monitoring at the Little Cayman aggregation site in both January and February. While fish did aggregate in January, no spawning was seen. February was (as expected) the "big" month and spawning was documented 7 nights after the full moon. The cleaning station stationary camera study was also continued. Movement data as recorded by the acoustic tags in 50 individuals around Little Cayman was also recorded, continuing the tracking research that was initiated in 2005. Thanks to a grant from the J. Edward Mahoney Foundation, Grouper Moon scientists started looking beyond the dynamics of the mature spawning adults on Little Cayman. As part of this work, REEF conducted a pilot study to expand the acoustic tagging project to the sister island of Cayman Brac, where Nassau grouper are in significantly lower densities and the two historic aggregation sites are apparently no longer active. In addition, a team of REEF surveyors searched for remnant Nassau grouper spawning aggregations at historic spawning sites on Grand Cayman in collaboration with CIDOE staff in Febaruary, and a Nassau grouper larval monitoring program using light traps on Little Cayman was initiated in collaboration with faculty from Oregon State University (OSU).

2006 Grouper Moon Project Summary

Throughout the remainder of 2005, staff from the Cayman Islands Department of the Environment (CIDOE) downloaded acoustic data from the hydrophones around Little Cayman Island and listened for acoustic pings on the other two islands (Grand Cayman and Cayman Brac). All but one of the 50 tagged fish have since been heard from sites on Little Cayman. The Grouper Moon researchers have now generated a map of home sites for each of the tagged fish - click here to view.The 2006 Grouper Moon field season started in January with a team of REEF volunteers - Leslie Whaylen, Denize Mizell and Brenda Hitt - and the CIDOE staff conducting daily visual monitoring and individual behavior documentation on the aggregation site. While lots of fish showed up (estimates up to 1,500) there was no spawning documented. Because the full moon was early in January, it wasn't too surprising. A second team of volunteers, as well as researchers from Oregon State University (Scott and Selina Heppell) joined the CIDOE staff on Little Cayman for the February full moon. During the aggregation cycle, over 3,000 fish were estimated on the site and lots of spawning was documented. During one of the spawning nights, several samples of spawn were collected to help estimate the total fecundity of the aggregation (i.e. how many eggs were released) as well for use in genetics studies. Based on rough estimates of number of fish in the water, number of spawning releases seen, and the number of eggs collected during one pass of the collection net, it is estimated that over 40 million eggs were released during just one night of the spawning.Based on the hyrdrophone data, 24 of the 30 fish that were tagged on the aggregation site in February 2005 revisited the aggregation in 2006. The remaining 6 are believed to have died sometime during the year (a 20% mortality, which is considered within range for natural mortality estimates for this species). Of the 20 fish that were tagged off the aggregation during the Spring/Summer of 2005, 5 are presumed to have died and 2 stayed on their home reef during the aggregation cycle. None of the tagged fish went anywhere other than the west end aggregation site.During the February aggregation, we placed stationary cameras on two active cleaning stations for one hour intervals during the day in order to record behavior and cleaning station activity. This project will allow Grouper Moon researchers to evaluate the role that cleaning stations play in maintaining the overall health of the Nassau grouper while they are at the aggregation site, as well as provide a better understanding of the multitude of behavioral interactions that lead up to spawning. This was the first year of this research, and our goal was to pilot a variety of camera settings and locations. A compilation of time-lapse video from a cleaning station, sped up 2x actual speed, can be dowloaded here (Windows Media Player, 12 MB) -- the video represents approximately 10 minutes over two days at one large sponge that served as an active cleaning station on the Little Cayman West End aggregation site. The Nassau grouper are seen flashing various colorations during their attempts to be in the primary cleaning location in the sponge. In addition to Nassau grouper, yellowfin grouper and tiger grouper occasionally show up to be cleaned (but rarely are allowed access for more than a few moments).

2005 Grouper Moon Project Summary

In 2005, a new component was added to the Grouper Moon Project to begin to address many of the unknowns about fish that visit the aggregation, such as “do fish attend the aggregation every year”, “where do the aggregating fish come from, ie. where is their home reef”, “what is the sex ratio of the aggregation”, and “what do the fish do during the aggregation cycle”, and more broadly to provide evidence (or lack thereof) that the harvest restrictions are warranted and merit extension beyond the 8-year sunset clause. Thanks to a grant from the NOAA International Coral Reef Conservation Program and additional funding from PADI Project AWARE, REEF initiated a multi-year acoustic tagging project on the Little Cayman aggregation. The acoustic project is a joint initiative with the Cayman Islands Department of the Environment (CIDOE) and is headed up by Brice Semmens from the University of Washington.The acoustic project involves the installation of 15 hydrophones around Little Cayman Island and acoustically tagging 50 Nassau grouper (30 during the aggregation and 20 this Spring from inshore reefs). The acoustic tags, which are surgically implanted in the belly of the fish, emit a signal that is picked up by the hydrophone if the fish passes within 500 meters. The hydrophones will record the presence of the tagged grouper for up to 3 years (before the tag battery wears out). Acoustically tagged fish are also tagged with an external Floy tag (often called spaghetti tags) so that they can be visually identified underwater. Blood and tissue samples are collected during the tagging process in order to look at hormone levels. Project collaborator and fish physiologist, Dr. Scott Heppell from Oregon State University, is coordinating the hormone assays.A team of REEF and CIDOE divers descended on Little Cayman Island during the January full moon. Several hundred fish were already at the aggregation site when the team arrived and by its peak, over 2,000 fish and copious amounts of spawning were seen. The ongoing aggregation characterization monitoring as well as the grouper migration study were both continued, under the direction of REEF volunteers Leslie Whaylen and Judie Clee, and the acoustic tagging project was successfully implemented. In an effort to reduce poaching, Raymarine Marine Electronics donated a RADAR unit to be mounted on shore in sight of the aggregation site. A very successful year!The acoustic tags will emit pings for up to 3 years. The CIDOE will download data from the hydrophones every three months and will use mobile acoustic gear to listen for grouper in areas that are not covered by the hydrophones (including on the neighboring islands of Grand Cayman and Cayman Brac). The waiting now begins, but early data already show interesting results, such as once at the aggregation site the grouper don't necessarily stay put but rather make extensive forays to reefs on other parts of the island during the day, returning in time for the action at dusk.PRELIMINARY RESULTS!! After the first three months of grouper movement data were downloaded, Brice created video files representing the movement of each tagged fish based on recorded pings. These movement videos were updated in January 2007 (incorporating movement up through December 2006). You can view these individual movies by visiting the acoustic tagging project movement videos page.In the Spring of 2005, 20 additional Nassau grouper were captured and tagged from around Little Cayman Island in order to better address the proportion of reproductive-size fish that are attending the aggregation each year. Unlike tagging on the aggregation, which is relatively easy with hook and line, capturing Nassau grouper during non-aggregating times when they are solitary is difficult. Therefore, baited fish traps (similar in design to Antillean fish pots) were constructed and deployed in sand patches in the late afternoon and retrieved the following morning, within 18 hours of deployment. Although the traps were efficient at catching Nassau grouper, several of the fish caught were infested with an isopod parasite (Excorallana antillensis). A sample of the parasite was collected and the infestation was photographically documented. The infestation and potential links to energetic costs assosicated with spawning have since been published in the journal Journal of Fish Biology (PDF posted here). Most of the infested animals were released without tagging, and 20 individuals were eventually captured through the use of hand nets. There is now a dedicated acoustic tagging project webpage - click here to visit. More to come, so stay tuned!

2004 Grouper Moon Project Summary

The big news this year is the bold and vital step taken by the Cayman Islands Marine Conservation Board to close all aggregation sites to fishing for the next 8 years! What a great reward for all the hard work put in by REEF and the CIDOE and the support of the Little Cayman dive operators. This important legislation was put in place just prior to the 2004 winter full moons. The REEF team, again led by Leslie Whaylen, arrived in Little Cayman Island in January with high hopes. Unfortunately very few grouper were found at the aggregation site and no spawning was seen. The team returned for the February full moon and this was the month. Over 2,000 fish were present at the aggregation during the peak days and over 100 spawning bursts were recorded. The team collected the standardized information over both aggregation cycles (Jan and Feb).

2003 Grouper Moon Project Summary

In January 2003, REEF returned to Little Cayman Island to continue the Grouper Moon Project. All of the aggregation research that was started in the 2002 project was continued and several new components were added, including time-lapse video surveys, underwater measurement of fish using lasers, and individual behavior documentation. In addition to working with the Cayman Islands Department of the Environment, REEF collaborated with researchers from North Carolina State University who used a split-beam echo-sounder and 3-D underwater video system to quantify the spatial structure of the aggregation. Several REEF volunteers stayed at the Southern Cross Club and conducted Grouper Migration surveys during their daytime dives. During the two-week project, public seminars were given on the spawning aggregation. Because 2003 was a non-fishing year in the newly implemented Cayman Islands grouper aggregation conservation law, the CIDOE worked with the Caymanian fishermen to explain and implement the closure. As a testament to the CIDOE’s outreach to the Caymanian public, no illegal fishing has been reported this year. The alternate fishing year strategy now protects eight aggregation sites within the Cayman Islands. Five days after the full moon in January 2003, approximately 1,500-2,000 Nassau grouper were observed. Based on last year’s observations, the team expected to see a major spawning event the next evening (6 days after the full moon). However, only 200 Nassau were observed with only a few gamete releases observed. Leslie returned to Little Cayman for February’s full moon. During the week-long project, she and the CIDOE staff documented over 2,000 Nassau grouper on several days and 4 nights of spawning. However, these spawning events were not as extensive as those observed in the January 2002 aggregation. To read a full summary from REEF's Spring 2003 Newsletter, click here.

2002 Grouper Moon Project Summary

Whaylen, L., Pattengill-Semmens, C.V., Semmens, B.X., Bush, P.G. and M.R. Boardman. 2004. Observations of a Nassau Grouper (Epinephelus striatus) Spawning Aggregation Site In Little Cayman, Including Multi-Species Spawning Information. Environmental Biology of Fishes. 70: 305-313.This paper summarizes the findings from the 2002 REEF Grouper Moon Project, which documented the characteristics of a newly discovered Nassau grouper spawning aggregation. At its peak, over 5,000 Nassau grouper were present at the site. Significant contributions include the visual and video documentation of four nights of spawning of Nassau grouper, the description of crepuscular and lunar movements and color phase shifts in the grouper, and the documentation of courtship/spawning behavior in ten additional species. Click here to view a PDF of this article. This paper was also presented at the 2002 Gulf and Caribbean Fisheries Institute Meeting.