We had just finished another incredible dive on the north wall of Grand Cayman, and back in the boat, my daughter Jessica, said “Dad! Did you see the number of small Nassau groupers on that dive, there were at least five or six! I don’t recall seeing that many a few years ago”.
“It’s definitely a positive sign.” I replied “You are witnessing the very beginning of a possible come back by a species that has been so over exploited, it is considered threatened.”
Among fishermen and divers this is one of the best known groupers in the southern USA, Bahamas and Caribbean. It was once one of the most important commercial groupers, reaching nearly three feet in length. This grouper has a unique colour pattern that I love to paint. There are dark bars on the head and body and a black blotch on the top of the caudal peduncle. The live along the fore reef and deep drop offs throughout their range, but nowhere are they common.
Many predatory reef species such as groupers, snappers, and jacks congregate in specific sites at specific times of year to spawn. The efficiency of this process has ensured the survival of the respective species over millions of years. It was a compromise between reproductive efficiency and avoidance of predators. Introduce man into this delicate balance and in the last five decades grouper and snapper populations throughout the Caribbean have been over exploited to the point where most species are severely depleted and some are considered threatened by the World Conservation Union.
According to my friend and fellow researcher Dr. Mike Domeier, these spawning aggregations are disproportionately responsible for the reproductive output of many economically valuable and ecologically important species, and they result in the concentration of individuals from stocks that are otherwise at low densities.
One of my greatest diving experiences was in Belize in 2003 where I filmed a documentary about spawning aggregations of cubera snappers, mutton snappers, and dog snappers. These aggregations were the remnants of once much larger schools, and were attracting the attention of divers and cinematographers, because the presence of juvenile whale sharks that fed on the massive volume of spawn produced by the aggregations, each evening. Over tens of thousands of years all these creatures’ migrations were synchronised to aggregate at these specific sites. In the blink of an eye in geological time, human expansion and demand for sea food has resulted in the decline of most fish species through unsustainable harvesting practices.
The Nassau groupers in the Cayman Islands used to congregate over the full moon in January and February at eight specific sites. Local fisherman have known about these sites for years, but recently, intense fishing at these sites has led to the rapid decline in this species. This is not typical in a Caribbean country that prides itself on strong marine conservation practices. Now one active site remains in Little Cayman, but there are signs that the other sites may be starting a recovery.
By comparison, in my native Jamaica, all reef species have been over fished largely by the unregulated use of fish traps and widespread spear fishing. Over fishing in the Cayman Islands came to my attention in January 2001, when local fishermen in Little Cayman and Cayman Brac took advantage of the annual Nassau grouper spawning aggregations and harvested several thousand spawning adults. There was a glut on the Sister Islands, and fishermen took their catch to Grand Cayman. They were met with resistance and indignation, and there was a popular outcry against the slaughter of spawning adults of this threatened species. So began the slow process of recovery but it took another two years for the protection of the spawning sites to be gazetted by the government. In 2003 the CI Marine Conservation Board mandated an eight year fishing ban on all known Nassau grouper aggregation sites.
Since then a number of research bodies, but particularly REEF, in collaboration with the Department of Environment, have initiated studies of the Nassau grouper at the remaining spawning sites. Other research organisations, such as the Guy Harvey Research Institute, have identified further key research needs. REEF has conducted a detailed survey the Cayman Islands to find out if historically known aggregation sites are being colonised again, and if other sites exist. Allowing the Nassau groupers to maximise their spawning activity is a critical step in helping populations recover.
These sites have now been identified by REEF and the DoE, and they have determined how the groupers use these sites, and where the fish in each aggregation come from. In addition the research suggests that the larval and juvenile groupers come from Cayman brood stock and not just from other islands up current, such as Cuba or Jamaica. Research work by REEF, has identified these patterns in Little Cayman, but there is need for further study in Cayman Brac and Grand Cayman where this species has not made as rapid a recovery as has been expected. The duration of protection for the Nassau grouper should be extended for another ten years to allow full recovery.
Many grouper species show strong site fidelity, so it is possible they use well travelled migratory pathways to and from aggregation sites. This type of information can be obtained by using modern acoustic telemetry techniques to track the fish. For example GHRI scientists are conducting a similar study in collaboration with the University of the Virgin Islands to understand migratory pathways of several grouper, snapper and shark species in relation to distribution and timing of aggregation sites between St. Thomas and Puerto Rico. Once these pathways are identified, the species may be better protected en route to the aggregation site.
The GHRI has been conducting DNA forensic surveys in many restaurants in Florida and have found that more than 50 per cent of fish served as grouper on the menu is some other species. Groupers have become so scarce that restaurant owners are substituting other species, because they cannot find the real thing.
So how can you help protect the Nassau grouper? Here are some recommendations from the Department of Environment.
Don’t buy or sell grouper in restaurants or supermarkets. You will help reduce up the demand for their meat. The Guy Harvey Island Grill does not offer any species of grouper, shark or billfish on their menu.
If you are fishing, don’t target groupers, and release the ones caught by accident. Even if they appear filled with gas, the bladder can be deflated and the fish returned to the reef.
You can assist in the protection of grouper habitat, which are the shallow lagoons for juveniles and the deep reefs for the adults.
You can educate others about the current decline of all grouper species.
Because of their fantastic markings, the Nassau grouper is a favourite of underwater photographers. In our islands where diving is such an important focus of our ecotourism product, people want to interact with healthy reef systems, and healthy fish populations. A large living Nassau grouper is much more valuable to Cayman’s economy than a grouper fillet on a dinner plate.
With the ban on fishing at the Nassau grouper aggregation sites, and with meaningful protection being given to the species by the CI Marine Conservation Board, the Nassau grouper has a good chance of recovering to pre-exploitation levels. For the next two months the Nassau groupers will be making their annual pilgrimage to their aggregation sites around the Cayman Islands.
Great diving,
Guy Harvey, PhD.
www.guyharveyinc.com