Black Margate

The Black Margate, Anisotremus surinamensis, is a robust and intriguing member of the grunt family (Haemulidae) that divers frequently encounter in the Western Atlantic. Known for its deep-bodied profile and often curious demeanor, this species is a fascinating subject for underwater observation.

Typically found in tropical to subtropical waters, the Black Margate's habitat spans from Florida and the Gulf of Mexico through the Caribbean Sea, extending southward along the coast of South America to Brazil. They prefer structured environments such as rocky reefs, wrecks, and coral formations, often seeking shelter in caves and under ledges during the day. Divers can spot them at depths of 10–50 m, though they can range from inshore waters down to 70 m, and occasionally even deeper to 109 m. They thrive in waters with preferred temperatures of 24.2–26.1°C.

Primarily nocturnal, Black Margates are often observed resting in small groups or as solitary individuals during daylight hours. At night, they emerge to forage, feeding opportunistically on benthic invertebrates such as crustaceans, mollusks, echinoids (like sea urchins), and small fish. This species is also known for its ability to produce a distinctive grunting sound by vibrating its swim bladder, a common trait among grunts. With a maximum recorded size of 64 cm (25 in), though some individuals can reach up to 76 cm (30 in) and weigh 5.8 kg (13 lb), the Black Margate is a substantial presence on the reef. Its conservation status is currently listed as Least Concern.

This species is commonly observed at dive sites such as Tormentos Reef.

Identification

The Black Margate possesses several key features that make it identifiable to divers:

• Body Shape: It has a distinctive deep, compressed body with a high back and a relatively short, blunt head.
• Coloration: The body is generally silvery-grey, often appearing darker on the anterior (front) half than the posterior (rear) half. The scales on its upper body may have dark centers, creating a faint crosshatched or lined pattern.
• Fins: All fins are typically dark grey to nearly black, with the pelvic and anal fins often being the darkest. A noticeable dusky or black patch is frequently present on the rib cage area, just behind the pectoral fins. The dorsal fin has a deep notch and is supported by 12–13 spines and 16–18 soft rays, while the anal fin has 3 spines and 8–10 soft rays. Dense scales are present on the bases of the soft dorsal and anal fin membranes.
• Head and Mouth: The mouth is positioned low on the head, horizontal, and features thick, fleshy lips.
• Juvenile Markings: Younger Black Margates exhibit striking black stripes along the lateral line and another along the upper back, along with a prominent black spot at the base of the caudal (tail) fin. These distinctive markings gradually fade as the fish matures.
• Other Features: At night, their eyes can appear to glow when illuminated by a dive light.

The Black Margate (Anisotremus surinamensis) is a fascinating species for divers to encounter, primarily inhabiting the warm, tropical to subtropical waters of the Western Atlantic Ocean. Its distribution stretches from Florida and the Bahamas, throughout the Gulf of Mexico and the Caribbean Sea, and southward along the coasts of South America to Brazil, including locations like Fernando de Noronha and Trindade Island. This grunt species shows a strong preference for environments offering structural complexity, which provides both refuge and foraging opportunities. Divers can typically find Black Margates in:

• Coral Reefs: They are commonly associated with reef-associated habitats.
• Rocky Bottoms and Ledges: The species has a particular affinity for steep, sloping rock substrates and rock reefs.
• Caves and Crevices: Black Margates frequently seek shelter in caves, under ledges, and within rocky crevices during the day.
• Shipwrecks: Wrecks also serve as important shelter features for this species.
• Patch Reefs: They are often found on larger patch reefs.

Black Margates are generally observed at depths ranging from inshore waters down to approximately 70 meters. While they are frequently found in shallower waters, typically between 0–20 m, records indicate their presence in mesophotic reef ecosystems extending to a maximum of 109 m. Preferred water temperatures for this species are typically between 24.2–26.1°C. While primarily a marine species, the Black Margate can occasionally be found in brackish environments. They are usually encountered as solitary individuals or in small groups, often resting during the day and becoming active nocturnal feeders, preying on crustaceans, mollusks, smaller fish, and sea urchins. Juveniles of the species have been observed settling on rocky seabeds off Florida.

The Black Margate (Anisotremus surinamensis) is a robust and intriguing member of the grunt family, often encountered by divers in the western Atlantic. With its distinctive stocky frame and bold markings, this species commands attention in its reef habitat.

Underwater Encounter Behavior

Divers typically encounter Black Margates as solitary individuals or in small groups, particularly during daylight hours when they are resting. They prefer to shelter in caves, under ledges, or within wrecks, often found in shallow to moderately deep waters, typically encountered at 0–70 meters, though they can range deeper. While generally cautious and sometimes shy, Black Margates have also been observed to display a curious temperament, occasionally investigating divers and objects in their environment with a deliberate, confident approach. This species is known to produce grunt-like vocalizations by grinding its pharyngeal teeth, a sound amplified by its swim bladder, which serves as a form of communication.

Feeding Habits

The Black Margate is a nocturnal benthic feeder. During the night, they emerge from their daytime shelters to forage on the seafloor. Their diet is opportunistic but specialized, primarily consisting of hard-shelled invertebrates such as crustaceans, mollusks, and echinoids (sea urchins). Larger adults, in particular, show a preference for sea urchins, which can constitute a significant portion of their diet. They utilize their strong teeth and powerful jaws to crack open their prey, moving deliberately rather than relying on speed.

Social Structure

Black Margates are most often observed alone or in small aggregations. They can exhibit territorial behavior, actively defending their chosen reef patches from other intruders. During the breeding season, they are known to form distinct pairs.

Seasonal Patterns

Reproduction for the Black Margate involves external fertilization, with distinct pairing behavior during the breeding season. Spawning occurs in aggregations, with peak reproductive activity reported between January and June in southeastern U.S. waters, with a notable peak in March. Off Jamaica, breeding adults have been reported between April and August. These seasonal aggregations can offer divers increased opportunities to observe this species.

Observed Dive Sites

• Tormentos Reef (common)