The Red Hind Bank Marine Conservation District (MCD) is a deep-water coral reef located along the shelf edge 8 miles south of St. Thomas, USVI. This area was closed seasonally in 1990 and permanently in 1999 to protect spawning aggregations of red hind (Epinephelus guttatus). Very little is known about the unique coral reefs or fishes that comprise this essential fish habitat. In an effort to determine how these management regulations have improved the red hind population CMES has conducted several studies funded by the National Marine Fisheries Service and University of Puerto Rico Sea Grant College Program. The objectives of these studies are to confirm the source area and movement patterns of red hind spawning within the MCD, document the sex ratio, size and number of red hind spawning within the MCD, and characterize the physical and biological features of this essential fish habitat.

To document movement patterns we utilize two tagging methods. The first is a tag-release-recapture program using anchor tags. Fish will be caught during the spawning aggregation, measured, tagged with numerically coded Floy anchor tags and released. A $20 reward will be offered for recaptured fish. To date, recreational and commercial fishermen have returned 22 tags. The second method utilized radio tags, which are implanted into the body cavity of the fish. Individual fish are tracked using an underwater hydrophone that is used to listen for the specific frequency and ping-rate of the implanted sonic tags.

As with most groupers, the red hind are protogynous hermaphrodites (fish are born female and become male later in life). Female to male sex ratios of 2:1 to 4:1 are normal but in heavily fished populations the ratio could be as high as 15:1 to 20:1 females to males. Since the ratio of females to males is very important to the reproductive success of these species, biologists use this ratio to determine the health of the breeding stock. Since it is unacceptable to use traditional methods of sacrificing fish to examine reproductive structures in the MCD, CMES is utilizing ultrasoundimaging as a non-invasive technique to determine the gender of red hind tagged from the spawning aggregation. Preliminary results indicate that ultrasound imaging is highly reliable in distinguishing mature males and females of live red hind without harming the fish. This same technology is used in medicine to examine the health of a human fetus inside the womb.

To estimate the density of red hind within the spawning aggregation, divers will count groupers along 30x2 meter transects. In order to maximize the time spent underwater, CMES divers receive technical training to use oxygen enriched air (nitrox) at depths of 100 to 140 ft. Divers also use nitrox to conduct underwater video transects of the coral reef. These videos provide the first quantitative assessment of red hind spawning habitat and the coral reef resources within the MCD.

These projects will allow local and federal fisheries managers to evaluate the usefulness of this and future Marine Fishery Reserves as a tool for the sustainable management of important grouper fisheries. Tag-return data and sex ratio data will give managers a regional perspective on the source areas and condition of grouper spawning stock, respectively whereas the benthic assessments provide the first quantitative information on the habitat preferences of spawning red hind groupers.