The red grouper boasts a unique physique, with a body length that is 2.6 to 3 times as long as its depth. Its subangular preopercle exhibits slightly enlarged serrations at the angle, while the upper edge of the gill cover remains straight. With three flat spines on the gill cover, the central spine stands out as the longest. This species showcases a dorsal fin containing 11 spines and 16-17 soft rays, along with an anal fin consisting of 3 spines and 8 soft rays. Notably, the pectoral fins surpass the pelvic fins in length, and the caudal fin is truncate. When it comes to coloration, red groupers display a dark reddish-brown hue on the upper part of their head and body, transitioning to paler pink shades on the underparts. They are further adorned with lighter spots and blotches across their body, complemented by darker margins on their fins. Red groupers can reach a maximum total length of 125 centimeters (49 inches) and weigh up to 23 kilograms (51 pounds).
The red grouper thrives in coastal areas of the western Atlantic Ocean. Its habitat spans from southern Brazil to North Carolina in the United States, encompassing the Gulf of Mexico and Bermuda. This expansive range allows the red grouper to establish a significant presence in various marine ecosystems.
As a demersal species, the red grouper tends to be predominantly sedentary, favoring an extended (~40 day) pelagic larval stage before settling in shallow coastal hardbottom habitats as juveniles. These fish remain in inshore waters for approximately 4-5 years before migrating to offshore hardbottom habitats, particularly on the continental shelf's edge, when they reach adulthood. The spawning season of the red grouper occurs offshore from January to June, peaking in May. While the primary diet of these groupers consists of benthic invertebrates, they also exhibit opportunistic feeding behavior within the reef community. Their menu often includes xanthid and portunid crabs, juvenile spiny lobsters, snapping shrimp, and occasionally, other fish. Red groupers typically measure around 125 cm in length and weigh 23 kg or more. Noteworthy is their ability to rapidly change coloration patterns, particularly when aggravated or engaged in spawning activities. During such instances, certain parts of their body, such as the head, may turn completely white, and the white spots become more prominent.
Red groupers play a vital role as habitat engineers in the marine ecosystem. They actively excavate pits in the seafloor, beginning the process as soon as they settle from the plankton stage and continuing throughout their lives. Using their caudal fins and mouths, they remove debris and sediment from rocks, creating exposed surfaces that attract sessile organisms like sponges, soft corals, and algae. This behavior also entices a diverse array of other species, including mobile invertebrates and a variety of fishes such as gobies, butterflyfish, grunts, and snapper. However, the invasion of lionfish (Pterois volitans) has posed a significant challenge to red grouper habitats since 2008. Scientists are actively studying the extent to which the presence of lionfish alters the functional dynamics of associated communities, given their prowess as predators of small reef fish.
As with other fish species, red groupers host a range of parasites. Notably, their gills serve as a habitat for monogeneans such as Pseudorhabdosynochus justinella and Pseudorhabdosynochus yucatanensis.
Formally described as Serranus morio by the French zoologist Achille Valenciennes in 1828, the red grouper holds a special place in taxonomic records. The type locality of the species is designated as the fish market in New York, with the presumption that the fish were likely caught south of that location.
The red grouper carries significant commercial importance for fisheries across its extensive range. Its popularity extends beyond commercial fishing to recreational fishing as well, making it a valuable resource for both sectors. The abundance of information provided in this article sets the stage for improved visibility and accessibility to those seeking knowledge about the red grouper.