The Nassau grouper (Epinephelus striatus) is a common commercially exploited fish, found in several coral reefs. It belongs to the Serranidae family, one of the largest and most widely distributed in marine waters. This species was once considered one of the most abundant in the world, although it is now critically endangered.
It is a predator that actively competes against barracudas, sharks and other fish. Thanks to the diversity of its coloration and its economic importance, it has been an important pillar for the fishing industry. However, it is currently facing risks that may threaten its population. Read on to learn more about this curious fish.
Habitat of Nassau grouper
The Nassau grouper is a tropical species, which covers a large part of the Atlantic Ocean coasts. It can be found in the Caribbean, Bermuda, Florida, the Yucatán Peninsula and Venezuela.
This species prefers shallow water reefs, but can reach up to 100 meters deep. It is also common to detect specimens in seagrass beds, holes, cracks and crevices with good visibility. For their part, juveniles select habitats with corals and high amounts of microalgae.
These organisms are Euryhaline, so they can tolerate different salinity ranges. In addition, as they grow, they change their habitat slightly. For this reason, they live in a wide range of ecosystems, as they are endowed with mechanisms that allow them to conquer diverse environments.
In terms of coloration, this species has a striped pattern similar to that of zebras, with colors such as pink-red, orange and white. In addition, adult specimens exhibit 5 dark stripes, which are distributed along the body, with a dorsal line that starts from the mouth and reaches the dorsal fin.
The largest fishes can reach up to 1.2 meters in length, but most of them stay around 72 centimeters. Similarly, their weight can reach 27 kilos, but the average is around 12 kilos.
Some specimens are capable of changing their coloration in response to a stimulus or as a sign of aggression. This tonal oscillation happens in minutes, going from its usual coloration with stripes to a much more uniform one. The chromatic variation depends on the “emotional” state of the organism.
Behavior of Nassau grouper
This species has a solitary behavior. Nassau grouper are silent predators and stalk their prey from holes or other cover. In addition, they prefer to hunt in the dark, so they are not very active during the day. In general, it is a very aggressive animal, even when it is in its breeding season.
According to a study conducted by North Carolina State University, these organisms also show a change of habitat as they mature. That is, when they are born they prefer to shelter in areas with abundant microalgae, in order to hide and have food. As they grow and gain size, this is no longer necessary, so they leave their hiding place and move freely.
In this way, their behavior keeps the species safe until they are big enough to face their predators. In addition, they are very loyal to the place where they are born, since they return to spawn in the same place.
Finally, it should be noted that the ability to change their coloration serves as a means to communicate with each other. Tonal variation can signify a warning or a call for copulation, among other things.
Species of grouper
Although we have talked here about the Nassau grouper, there are other species that are part of the serranidae family. Among them, the best known are the following:
- Red grouper (Epinephelus morio): very common in the coasts of the Gulf of Mexico, this fish can measure up to 125 centimeters in length. Its color is reddish-brown.
- Black grouper (Epinephelus nigritus): a fish that can reach 230 centimeters in length. It is distributed in the western Atlantic, in the Gulf of Cariaco, Venezuela. It is also called “bartotero grouper”.
- Snapper grouper (Epinephelus analogus): this species reaches 104 centimeters in length and is distributed in the eastern Pacific regions, from California to Peru and the Galapagos Islands.
- Guasa grouper (Epinephelus itajara): this is an organism capable of reaching 175 centimeters in length. Its distribution covers the Atlantic and Pacific regions, some of which coincide with that of the Nassau grouper.
The Serranidae share many of the same characteristics. However, some main differences between taxa tend to be their weight, size and geographic distribution.
Feeding of Nassau grouper
These groupers can be considered generalist predators, but they have a unique method of engulfing their prey. To catch them, they create suction through their gills, which allows their food to enter the mouth quickly and with minimal energy expenditure.
As it grows, the size of the prey consumed by this species also increases. While juveniles eat some crustaceans or bivalves, adults feed on fish, lobsters and gastropods.
Reproduction of Nassau grouper
This fish is considered a hermaphrodite, since it is born with both gonads immature, but when it reaches adulthood it develops as a male or female. Its reproductive mechanism is even more intricate, as Nassau grouper have the ability to detect changes in lunar phases, so their biological clock is closely related to them.
Nassau grouper form groups in order to reproduce, but this is the only time they are considered sociable. Between December and January, only one night a year and with a full moon, the specimens gather to spawn in a specific site. This site is located at the edge of the reef, in shallow water, where about 100,000 of them spend more than 3 days fertilizing the eggs.
The egg hatches and the hatchlings are born after 24 to 48 hours in the water. The first movements of the hatchlings are always to look for a place to shelter. At this point, the parents do not give any parental care to the offspring: once the spawning is over, they leave the place.
The young mature slowly, and when they reach 4 to 8 years of age, they reach the reproductive stage. From this moment on, they will finish their development and transform into females or males, at which time the life cycle repeats itself.
State of conservation
One of the major problems of this species is overexploitation, since it was originally a fairly abundant fish in its original area of distribution. Unfortunately, after years of plundering, the Nassau grouper is listed as “Critically Endangered (CE)”, according to the International Union for Conservation of Nature.
Despite the existence of programs to regulate its fishing, this organism continues to show a reduction in its population, as sustained as it is worrying. This only means that efforts are not enough, so it is likely that more severe actions are needed.
This species has some of the most amazing characteristics, from its changing coloration patterns to its behaviors. That is why one possible solution to their problem is to encourage ecotourism, which would help conservation and produce profits. In some cases, nature and man can reach a balance, or at least that is what we should aspire to.