The grouper monitoring program in Kadavu was started by Dr. Yvonne Sadovy and Rick Nemeth from the Society for the Conservation of Reef Fish Aggregations in 2008. Dr. Sadovy assembled an international team consisting of local fisheries officers and local and international scientists to monitor the number and type of groupers in the area.
The area is used by several groupers and many other species for spawning so it was established as a marine protected area (no-take zone) managed by the local village. The main grouper that spawn at the site and are being monitored include the Camouflage grouper (Epinephelus polyphekadion), Brown marble grouper (E. fuscoguttatus), Squaretail coralgrouper (Plectropomus areolatus) and Black saddle grouper (P. laevis).
The study team consisted of me, Brad Erisman a professor of Marine Biology at Scripps Institution of Oceanography in San Diego, California, USA and Rick Nemeth from the Conservation of Reef Fish Aggregation in the Virgin Islands. Our research was supported by Siwa, the dive master, and Tulala the boat captain. We dove three times per day for six straight days, and we saw a lot of groupers. On the first day of diving, Brad and I saw approximately 50-60 Brown marble grouper and a few small groups of Camouflage grouper and Black saddle grouper. Rick didn’t arrive until the next day, because he was delayed because of a hurricane that was passing by his home in the U.S. Virgin Islands.
For the rest of the week, we did not see many Camouflage grouper or Brown marble grouper, which suggested that these fish were not spawning at the time of our visit. For the Camouflage grouper, we suspect they have spawned already, whereas the Brown marble grouper may have spawned just before we arrived (before the full moon). However, with each passing day, we observed more and more Black saddle grouper. Many of these fish were really large – more than 90-100 cm in length and weighing more than 10 kg. The largest ones took on a brilliant coloration with dark gray on their head, front and back of their bodies but with a large white stripe down the middle, a bright white belly and lips. After three years of working at this site, this year seems to have the highest count of Black saddle grouper. These fish would swim by other groupers, turning their bodies to the side and shaking their head violently back and forth. While we are not sure exactly why these fish were behaving this way, in other groupers this behavior occurs in aggressive behavior between males as well by males attempting court and spawn with a female. By the end of the trip, we estimated that there were as many as 135 Black saddle grouper in our survey area.
In 2010, Rick Nemeth had placed three acoustic receivers on the reef to record the presence of any tagged camouflage grouper as they move in and out of the area to spawn. The portion of the project related to the receivers was set to finish this year, so we decided to retrieve all the receivers this week as well.
Overall, the trip was a great success. The entire staff at the resort was wonderful, generous, and helpful to us throughout our trip. We were invited by the chief and the staff to take part in a kava ceremony, where we learned a lot more about the local communities and their resources. Of course, we also accomplished all our research goals for the trip. Hopefully, if we are lucky, next year when we return we’ll get to see the spawning of the Black saddle grouper.