The Nassau grouper is a predatory fish that lives on the coral reefs of the Caribbean Sea and adjacent waters. Its name comes from its historically large populations in the Bahamas. The Nassau grouper, like most groupers, is an ambush predator and eats fairly large fishes and invertebrates, including large crabs and lobsters.
Caribbean reefs with large numbers of predators, like Nassau groupers, are known to be healthier than reefs with no predators, so this species may represent an important part of the reef food web. During the majority of the year, Nassau groupers are reddish brown in coloration, with vertical light bars along the head and body. During mating, however, males become black on top and white below and females become almost solid black. Nassau groupers feed by swallowing their prey whole; they do not chew. They use their very large mouths to create enough negative pressure to suck in whole fishes or lobsters, and they swallow them quickly and efficiently.
Nassau grouper reproduce in only a few places and during only a few months each year. These fish always spawn immediately after the full moon during the winter months, when they form very large groups called spawning aggregations. Throughout its entire geographic range, there are less than 100 known spawning aggregation sites where Nassau grouper reproduce year after year, and historically these aggregations included hundreds, if not thousands, of individuals reproducing together for a few days before returning to their home reefs. Individual Nassau groupers are known to travel several dozen miles and further to form part of a spawning aggregation. At the aggregation sites, these fish reproduce by a method known as broadcast spawning, where females release eggs and several males release sperm into the water column above deep reefs all at the same time. This method increases the likelihood that eggs will become successfully fertilized and that fertilized eggs will not be eaten by egg predators on the reef surface.
While they were historically very common, Nassau groupers are now considered to be endangered by scientists. The behavior of forming dense spawning aggregations, where all the individuals from several square miles meet in once place, makes them an easy target for fishers. Even fishers who use relatively low impact methods (like hook and line fishing) have proven an ability to lower Nassau grouper numbers to dangerous lows. These fish utilize the same, few locations and same, few days for spawning every year, so their presence is quite predictable. Furthermore, once a spawning aggregation has been fished to zero, scientists fear that they may not ever recover. Unfortunately, several documented aggregations throughout the Nassau grouper’s range no longer form. While considered endangered, Nassau groupers are still fished in many places around the Caribbean, but scientists and conservationists have been successful in having them protected during their spawning season, in an effort to help this valuable and ecologically important species recover.