A collaborative conservation program between REEF and the Cayman Islands Department of the Environment
2002 - Present
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This was our fifteenth year conducting research on the Nassau Grouper spawning aggregation on Little Cayman. Our team went to Little Cayman around full moons in both January and February this year (because it was considered a “split year”, meaning the full moon dates were right on the line of predicting which month would be the strong spawning month). February turned out to be the big month, and spawning was seen over 3 nights starting 3 nights after full moon. Our team collected the annual monitoring data necessary to track the growth and changes. These data include visual estimates of aggregation size, individual sizes, and behaviors. On nights of spawning, we collected egg samples to estimate fertilization rates and for later genetic studies.
New this year was a collaborative INSPIRE study, funded by NSF and conducted with engineers and acousticians from Scripps Institution of Oceanography, to investigate the soundscape of the spawning aggregation site and resulting planktonic spawn clouds. This work involved several high-tech, innovative technologies including a large hydrophone array that measured sounds made by fishes in 3-D space and an underwater microscope. More to come from this study in the future.
We continued our successful Grouper Education Program. In November 2015, our educator held a Teacher Workshop in the Cayman Islands to train participating teachers. In January, we conducted four live-feed webcasts with participating classrooms - three topside chats with scientists and one from underwater at a coral reef site along Bloody Bay Wall. All webcasts are archived on YouTube on TheGrouperTeacherREEF channel online here. Over 200 students from 17 schools participated.
A team of researchers conducted field research on the Little Cayman Nassau grouper spawning aggregation following the full moon in February 2015. Over 12 days, we conducted three dives each day on the aggregation site. Early in the 12-day spawning cycle, the researchers noticed that the Nassau grouper were not in their historical location. After searching the adjacent areas with underwater scooters, the aggregation was ultimately found about 500m to the north. Thankfully, we were able to adjust our equipment and field support in order to sufficiently accomplish all of our planned research objectives. The research team has not previously seen this type of relocation, and it will be interesting to see what the fish do in 2016.
Once the aggregation was located, the research dive team carried out routine visual census monitoring protocols to document population estimates and size-class distributions of spawning individuals. The team also deployed GoPro video monitoring stations throughout the spawning aggregation site to monitor fish movement and behaviors. On nights of spawning, we collected samples from the spawning bursts, using a method piloted in 2014. Following collection, the eggs were taken back to a lab facility on Little Cayman (Central Caribbean Marine Institute; CCMI) and maintained in aquaria until they hatch as larvae. Based on this work, we were able to calculate egg fertilization rates for both species.
We also started work to repeat the acoustic tracking study that was originally conducted in 2006-2008. Our team acoustically tagged 20 Nassau Grouper and 15 Tiger Grouper, another species that spawns at the Little Cayman site. These data will identify movement patterns and home reef locations.
We continued to grow the Grouper Education Program (GEP) in 2015, with continued support from the Disney Conservation Fund. The GEP is a marine sciences curriculum for elementary and high school students. REEF began developing this project in 2011, and it functions as an educational component to the Grouper Moon Project. The highlight of the GEP curriculum is the series of live-feed, video sessions that we facilitate between school classrooms and researchers in the field (often while the researchers are underwater). Three live-chats were held during the January 2015 field season. Over 300 students from 15 classrooms at 10 schools participated in the webchats. As part of the GEP, we held our first "Family & School Community Event" on Cayman Brac in February 2015. We shared research findings and information about the education program with local families and educators.
In order to share information about REEF’s work in the Cayman Islands and facilitate application of our findings to other areas of the Caribbean, we shared our research findings through publications and scientific meetings. Project PIs presented findings at the Gulf and Caribbean Fisheries Institute conference.
In 2014, our team went to Little Cayman around full moons in both January and February because it was considered a “split year”, meaning the full moon dates were right on the line of predicting which month would be the strong spawning month. February turned out to be the big month, and spawning was seen over 3 nights starting 3 nights after full moon. Watch a short video montage of the aggregation and spawning action here - http://youtu.be/GwKVzPLgmbo
This year, we tested out some new techniques for collecting and rearing fertilized eggs (in the montage video you will see a diver swimming through a spawn cloud with a plastic bag). After collecting Nassau grouper eggs during the two nights of peak spawning, Scripps scientists and REEF Grouper Moon Project volunteers cultured the eggs at the Central Caribbean Marine Institute on Little Cayman. After one night, a subset of eggs were preserved for research on fertilization rates. After two nights, the eggs had hatched, and researchers were surprised to find larval Nassau swimming around the tank the next morning. Check out this video of larval Nassau grouper under the microscope - http://youtu.be/0Vph6LzH9IE
In addition to the research, once again led an educational program surrounding Nassau Grouper and spawning aggregations. Thanks to support from Disney Worldwide Conservation Fund, we have created an exciting K-12 education curriculum rooted in the link between healthy reef communities (including humans) and healthy spawning aggregations. See the January 2014 REEF newsletter for more about the Grouper Education Program.
The Grouper Moon Project wouldn’t be possible without the dedication, passion, and financial support from many individuals, Cayman Island businesses, and foundations. It truly takes a village to pull off this conservation research project. In 2014, we especially appreciate the continued generous logistical support provided by Peter Hillenbrand, local lodging and dive operators Reef Divers & Little Cayman Beach Resort and the Southern Cross Club (especially Neil van Niekerk and the crew of the Lucky Devil for taking our team out in January), and Brac Reef Resort. Funding from the Disney Worldwide Conservation Fund supported field efforts and the Grouper Education Program. LIME Cayman Islands has provided support for the live-video feeds for the Grouper Education Project since 2012. Cayman Airways provided inter-island travel support. And the staff at Central Caribbean Marine Institute provided research space for the fertilized egg work. Thanks also to our scientists, volunteers, and partners who made this year's efforts possible - Adam, Alex, Brenda, Bradley, Croy, Guy, Hal, Ivan, James, Josh, Keith, Leslie, Laura, Lynn, Paul, Steve, and Todd.
We continued to document increases in the number of fish at the site and there were many "teenagers" (6-8 year olds, coming to spawn for the first time). The number of spawning bursts and the number of nights spawning occured has increased. Watch this short video to see the action. We continued our education efforts. With support from the Disney Wildlife Conservation Fund, we were able to expand the program to more classrooms at Cayman Prep and High School on Grand Cayman and initiated the program at Spot Bay Primary School on Cayman Brac. The Grouper Education Project introduces children to the ecological, economic, and cultural role that Nassau Grouper have in the Cayman Islands and wider Caribbean. An integrated marine science curriculum has been developed with a focus on two age groups (Grade 4 and Grade 11), that includes a series of classroom lessons and live from the field web sessions, including a live-feed from 80 feet on the aggregation. Seattle-based educator, Todd Bohannon, leads up this effort.
Photos from this year's work are posted in this album on the REEF Facebook page here.
The Grouper Moon Project wouldn’t be possible without the dedication, passion, and financial support from many individuals, Cayman Island businesses, and foundations. It truly takes a village to pull off this conservation research project. In 2013, we especially appreciated the continued generous logistical support provided by Peter Hillenbrand, local lodging and dive operators Reef Divers & Little Cayman Beach Resort and the Southern Cross Club, and Brac Reef Resort. Funding from the Disney Worldwide Conservation Fund supported field efforts and the Grouper Education Program. LIME Cayman Islands has provided support for the live-video feeds for the Grouper Education Project since 2012. Pegasus Thrusters supported the project in 2013 through the donation of Diver Propulsion Vehicles.
2012 was a very exiting year - we documented significantly higher numbers of fish at the site than in previous years (we are estimating that the aggregation has surpassed 4,000 fish), there were a lot of small fish this year (6-8 year olds, coming to spawn for the first time), and there are hundreds of juvenile (young-of-the-year) Nassaus throughout the shallow habitats around Little Cayman (a result of 2011 spawning). Also this year, with support from the Disney Wildlife Conservation Fund, we initiated an education program to introduce local children to the ecological, economic, and cultural role that Nassau grouper have in the Cayman Islands and wider Caribbean. An integrated marine science curriculum is being developed with a focus on two age groups (Grade 4 and Grade 11), that includes a series of classroom lessons and live from the field web sessions, including a live-feed from 80 feet on the aggregation. We are working with educator, Todd Bohannon, and piloting this program with Cayman Prep school on Grand Cayman. Click here to view a short clip of the underwater live-link, showing project scientist Dr. Brice Semmens answering qustions from students while underwater.
Other highlights from Grouper Moon 2012:
To raise awareness about the importance of spawning aggregations and the iconic Nassau grouper, we hosted documentary crews and underwater photographers to help capture the magical scenes of spawning and document our research. Dr. Guy Harvey, famed marine artist, is putting the finishing touches on "Mystery of the Grouper Moon", an hour-long show that will air later this year. A crew from the PBS series "Changing Seas" is producing an episode about the conservation impacts of our research. Paul Humann, REEF co-founder and marine life photographer, was on hand to document REEF's work in this important project. And Jim Hellemn brought his custom camera rig to generate wide-angle panorama images of the aggregation. These will be used to "immerse" the viewer into the aggregation at public displays; On spawning nights, samples of fertilized eggs were collected to use in future genetic work, to better understand spawning patterns and inter-conectedness between Nassau grouper populations throughout the Caribbean; Cynthia Shaw, author of the book "Grouper Moon", joined the REEF team both in the field and in the classroom this year. As a scientific illustrator, Cindy lent her expertise to helping document the details of juvenile Nassau grouper habitat and led our Cayman Prep classrooms in drawing Nassau grouper. Cindy's book is now available in the REEF online store here; Research findings from the project, describing the timing and behavior of color phases on spawning in Nassau grouper, was published in a recent issue of the scientific journal Current Zoology. You can read this paper online here; A short compilation of underwater footage from the spawning aggregation is posted on YouTube here.
This year's effort came on the heals of the 11th hour extension of protections for the spawning aggregations in the Cayman Islands. An 8-year ban that prohibits fishing at the aggregation sites during the reproductive season, originally implemented in 2003, was extended for eight more years in December 2011. The extension, enacted by the Marine Conservation Board, was in response to recommendations made by the CIDOE based on research findings of the Grouper Moon Project, showing that full protections during spawning season are critical to the long-term survival of this iconic species in the Cayman Islands. The Cayman Ministry may soon review a package of more thorough legislation that would enact seasonal closures for Nassau grouper during reproductive time (rather than only protecting the few spots on the map of known spawning sites).
During the 2012 field season, we were also joined by a crew from the PBS Emmy-award winning series, Changing Seas. They produced a half-hour segment about our research and outreach efforts, which is posted online here.
Our work this year focused on the spawning aggregation in Little Cayman, which is the largest (and one of just a few) known remaining aggregations of Nassau grouper in the Caribbean. REEF launched the Baby Grouper Adrift! webpage, which shows the results of state-of-the-art satellite drifter research being conducted. Working with scientists from Oregon State University, the Adrift project aims to better understand where Nassau grouper larvae end up after being spawned. Webpage visitors can follow the current drifters in real time as they complete a 45-day ocean journey (the amount of time Nassau grouper larvae spend floating in the currents), and even take a guess where the drifters will end up. Visit the webpage at http://www.REEF.org/programs/grouper_moon/adrift
Other highlights from the 2011 season include: In addition to copious amounts of Nassau grouper spawning documented in both January and February, several hundred tiger grouper were seen spawning over multiple evenings in February. Watch this video to see the tigers spawning!; world-famous marine life artist and conservationist, Guy Harvey, accompanied the Grouper Moon team this year to film a documentary on the project.; the 2010 Our World Underwater scholar, Josh Stewart, joined the project to help document our research. Josh will be working with REEF over the next several months to develop outreach materials that educate the public on the importance of spawning aggregations. To read more about Josh’s year as an OWU scholar, check out his blog – http://owussnorthamerica.org/; and, Wayne Sullivan once again donated his time and his vessel, the Glen Ellen, along with her crew, to support tech diving operations. This year, they helped answer many unknowns at the Little Cayman site, including how deep the Nassau grouper are found during the day and during spawning (at least 150 feet), and whether the fish spawn after dark (yes!).
A short video of the aggreagation from 2011 is posted here -- http://www.reef.org/reef_files/REEF2011NassauGrouperSpawning.mov
2011 is a critical year for the Nassau grouper of the Cayman Islands. An 8-year ban on fishing at spawning aggregations is due to expire this year. Sometime in early spring, members of the Cayman Islands Marine Conservation Board and the CI Government will be deciding what, if any, protections will be enacted to replace the expiring ban. Based on research findings generated over the last 9 years, we know that Nassau grouper only reproduce during their spawning season (winter months around the full moons). The research has also shown that prohibiting fishing during the spawning season has resulted in higher numbers of this endangered species in Cayman waters, benefiting everyone, including future generations of Caymanians, divers and snorkelers, and fishermen. A healthy population of Nassau Grouper is also critical for healthy and productive coral reefs. The government is seeking input on extending protections.
During the spawning season of 2010, the Reef Environmental Education Foundation (REEF) researchers and volunteers worked with the Cayman Islands Department of the Environment (CIDOE) personnel on both Little Cayman and Grand Cayman to monitor and acoustically tag fish on a remnant spawning aggregation (Grand Cayman), and to monitor the status and recovery of a healthy aggregation (Little Cayman). In addition to fieldwork, project scientists were busy synthesizing the data collected to date. Several presentations were made at the Gulf and Caribbean Fisheries Institute (GCFI) annual meeting in Puerto Rico (November 2010) based on results from the project. Additionally, PI Dr. Brice Semmens presented key findings from the project to the Minister of the Environment and his staff. The Director and lead scientists from CIDOE also attended the talk and participated in a discussion with the Minister following the talk.
Monitoring on the Little Cayman aggregation consisted of video-based laser caliper measurements of fish sizes on the aggregation, video pans of the aggregation to estimate abundance, visual estimates of abundance, and Floy tag mark-recapture estimates of abundance. On Grand Cayman, a team of closed-circuit rebreather certified divers (both volunteers and CIDOE personnel) spent the week exploring the east end aggregation site, which was discovered in 2009. Monitoring this aggregation proved difficult even on rebreathers because of the extreme depth and constant currents. Despite these challenges, the divers were able to garner visual estimates of grouper abundance, witness spawning, and video the aggregation on several nights. The aggregation on Grand Cayman is very small – approximately 500 fish. Tagging work on the island to date suggests that this aggregation is the only functioning aggregation remaining. The size of the aggregation on Grand Cayman, and its contemporary uniqueness on the island, suggests that Nassau grouper are on the brink of extirpation; it is imperative that we successfully complete our research goals on the island so we can fully demonstrate the seriousness of the threat facing this species and fishery.
Two Ph.D. students – Stephanie Archer (Oregon State University) and Alexis Jackson (U.C. Santa Cruz) – have incorporated aspects of the Grouper Moon program into their dissertation research. Both students are on track to submit manuscripts associated with this work in 2011. Stephanie has taken on the analysis of the laser caliper fish measurements and the video surveys to estimate the number of aggregating grouper. Her study (presented at GCFI in November 2010) uses both estimates of abundance and changes in size class distributions through time to demonstrate ongoing recovery of the Little Cayman spawning aggregation. This finding is good news, since it demonstrates that protecting spawning aggregations can be an effective prescription for recovery of Nassau grouper. Alexis is using mitochondrial and microsatellite DNA markers to assess how populations of Nassau grouper throughout the Caribbean are interconnected. To do this she is using tissue samples from the Caymans, the US Virgin Islands and the Bahamas. We are currently working with colleagues throughout the region to get additional geographic representation. Alexis’ talk on her preliminary findings at GCFI won best student presentation, and we expect that her findings will be both high-impact and or broad interest to managers and conservation practitioners.
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.
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.
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).
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).
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!
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).
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.
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.