THE GROUPER MOON PROJECT
A collaborative conservation program between REEF and
the Cayman Islands Department of the Environment

Yearly Project Summaries

2006 Project | 2005 Project | 2004 Project | 2003 Project |  2002 Results  

BACK to the Main Grouper Moon Page

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!

PICTURES FROM THE 2005 ACOUSTIC TAGGING PROJECT

15 hydrophones were installed around Little Cayman island to listen for pings emitted from the acoustic tags.	Fish were caught using hand lines and were weighed and measured.
A small incision was made and an acoustic tag was inserted inside the belly.	Each acoustically tagged fish was also tagged with an external Floy tag for visual identification.
At it's peak, over 2,000 Nassau grouper were seen on the Little Cayman aggregation in January 2005.  Photo by Scott Heppell.

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

The 2003 REEF and CIDOE Team at the Southern Cross Club. Click on the image for a larger version.

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 read the abstract or here to download a PDF of this article.  This paper was also presented at the 2002 Gulf and Caribbean Fisheries Institute Meeting.