The MSI interns swam with a few rare creatures this afternoon as they completed 16 fish follows focusing on parrot fish and their eating habits. "We swam through a really cool tunnel" said Eliza, "and we stalked queen parrot fish... And then we found ten big Black Groupers!"
Although the black grouper maintains an abundance elsewhere, they are endangered here in Bermuda. Due to its small size, Bermuda can only support a certain amount of black groupers, and these numbers have been severely threatened by overfishing.
The overfishing of the black grouper began in the 1980s with the use of fish pots. As a major contributor to the tourism industry and Bahamian food culture in general, the Nassau Grouper population was quickly declining throughout the Caribbean. The government issued legislation in 1984 to reduce fish pots, but it was not until 1990 that they were banned entirely.
Black Grouper are a K – selected species, which means that they have low fecundity (reproductive potential), slow growth, and late maturity. These factors contribute to its slow breeding cycle (which takes its course over at least seven years). Before they move into deeper water for spawning, juvenile Black Grouper spend at least one to four years in patch reefs, leaving them as easy targets to fishermen desperately in need to keep up with the growing demand for fish stock globally. However, due to the depletion of stocks in shallower water in the past 30 years, fisheries are beginning to move farther off shore into deeper waters, which is the spawning ground for adults.
Groupers are so named because they tend to participate in Spawning Aggregations, or SPAGs. During a SPAG, a large number of groupers gather in one place at a certain time of the year to breed. The breeding tendencies of groupers were not fully understood until recently, so initial fisheries laws did not account for them. To further complicate things, if the number of groupers at a SPAG does not reach critical mass, no breeding will occur making breeding rare with depleting numbers. SPAGs also make groupers susceptible to overfishing because a fishing boat that knows where the breeding grounds are can take away enormous catches. However, predictable breeding grounds have proven to be valuable to the grouper population of the Bahamas, and could prove to work in Bermuda as well.
In Bermuda, breeding grounds are off limits to fishing boats during the breeding season. In order to find the location of SPAGs, many groupers were implanted with acoustic tags in 2008. A boat can drop a hydrophone underwater, and then listen for the message these tags send, which identifies the tags' assigned number. If a tagged grouper is in range, the hydrophone will identify it, and give an estimation of its range based on volume. This lets the scientists easily search for concentrations of groupers.
Studies on a well known aggregation site in the North-Eastern seasonally protected zone revealed that the spawning season is longer than was previously thought. These studies lead to an extension of the protection of the spawning grounds. Another significant discovery was found in 2010: A second aggregation site in the southwestern seasonally protected zone, which attracts hundreds of groupers.
The black grouper is protected in 3 ways: Firstly by a regional ban regulating fishing inside the spawning area. Secondly it is protected by a seasonal ban regulating fishing during the spawning season. Thirdly there is a catch limit which does not allow people to catch more than one black grouper per boat per day.
Even if protected, with the long life cycle that groupers have, their intrinsic rebound potential will still be low. Identifying these breeding grounds and allowing for populations to begin recovering is necessary for this species survival.