Sandbar Shark, Carcharhinus plumbeus
Sandbar Shark, Carcharhinus plumbeus. Fish caught in the Cooper River, South Carolina, March 2011. Length: 1.27 m (4 feet 2 inches). Catch, photograph, and identification courtesy of Josh Leisen (joshadventures.com), Gaylord, Michigan.
Sandbar Shark, Carcharhinus plumbeus. Fish caught from coastal waters off Sanibel Island, Florida, February 2021. Length: 1.27 m (4 feet 2 inches). Catch, photograph and identification courtesy of Marc Eberlein, Grand Rapids, Michigan.
The Sandbar Shark, Carcharhinus plumbeus, is a member of the Requiem Shark or Carcharhinidae Family, that is also known as the Brown Shark and the Thickskin Shark and in Mexico as tiburón aleta de carton. Globally, there are thirty-five species in the genus Carcharhinus, of which seventeen are found in Mexican waters, seven in the Atlantic, four in the Pacific, and six in both the Atlantic and Pacific Oceans.
The Sandbar Shark is a medium-sized shark with a stout body. They are bronze to gray dorsally transitioning to white ventrally. They are dark gray-blue to brown dorsally and transition to white ventrally. Their head has a moderately rounded snout that is shorter than the width of the mouth, small round eyes, and the mouth is equipped with upper teeth that are broadly triangular that are straight in front and oblique on the sides and finely serrated lower teeth with narrow sharp points. Their anal fin mirrors the second dorsal fin; their caudal fin is strongly asymmetrical with a well-developed large lower lobe and an undulating ridge along the dorsal surface of the top lobe with a notch under the tip; their first dorsal fin is high and triangular, and originates slightly before the pectoral fins; their second dorsal fin originates over the anal fin origin; and their pectoral fins are broad, curved and long. They have a prominent interdorsal ridge. They have 5 pairs of gill slits, the last 2 originating over the pectoral fin base.
The Sandbar Shark is a demersal species that is found in both inshore and offshore over sandy and muddy bottoms in bays, estuaries, flats and harbors with salinities in excess of 20 ppt, and on bank, near islands, and flat reefs in open water. They are found from the surface to depths of 500 m (1,640 feet). They are found as solitary individuals or in sex-segregated schools that vary in size. They are known to make long seasonal migrations based on water temperatures moving to cooler waters in the summer and to warmer waters in the winter with males traveling in groups and females as solitary individuals. They are one of the largest coastal sharks reaching a maximum of 4.5 m (14 feet 9 inches) in length and 240 kg (529 lbs) in weight with females being larger than males. As of January 1, 2023, the International Game Fish Association world record stood at 240 kg (529 lbs) with the fish caught in coastal waters off the Archipelago des Bilagos, Guinea-Bissau in April 2002. They are an opportunistic bottom feeder that feeds on a wide variety of small schooling fish, rays and amphipods, bivalves, conchs, crabs, octopus and shrimp. In turn the juveniles are preyed upon by the Bull Shark, Carcharhinus leucas, the Great White Shark, Carcharodon carcharias, and Tiger Shark, Galeocerdo cuvier; the adults do not have predators. Reproduction is viviparous and involves a 2- or 3-year cycles with 11 to 12-month gestation periods and litter sizes of 6 to 10 pups that appear as miniature adults. Parturition occurs in shallow water where the juveniles remain until the fall, then migrate to deeper waters and then return in the spring. At birth, the pups measure between 40 cm (16 inches) and 53 cm (21 inches) in length They are normally present in 1:1 sex ratio. They have lifespans of up to forty-one years with females living longer than males.
The Sandbar Shark is a resident of Mexican waters of the Atlantic Ocean being found throughout the Gulf of Mexico; they are absent from along the east coast of the Yucatán Peninsula in the Caribbean. In the Pacific it has a very limited range in the Pacific being found only around the Revillagigedo Islands.
The Sandbar Shark is most likely confused with the Bull Shark, Carcharhinus leucas (thick body, large pectoral fins), the Dusky Shark, Carcharhinus obscurus (slender body, large round eyes), the Finetooth Shark, Carcharhinus isodon (very pointed snout), the Narrowtooth Shark, Carcharhinus brachyurus (long straight pectoral fins) and the Reef Shark, Carcharhinus perezii (anal, caudal and pectoral fins with black margins).
From a conservation perspective the Sandbar Shark is currently classified as VULNERABLE. Although widely distributed they are long-lived, late maturing, with low fecundity and prone to heavy fishing pressure and human-induced habitat destruction of their inshore habitats. The United States has banned all commercial landings. They remain, however, unregulated and one the most important shark catches in the Gulf of Mexico being caught with longlines, trawls and set nets. Amounts, fish sizes, and fewer and fewer females are being caught. The numbers of juveniles being caught has significantly increased. These sharks have also become of greater interest due to the demise of the Swordfish and Tuna fisheries. They are also a sizable portion of the artisanal fishery catch on the west coast of mainland Mexico. Their meat is considered to be good and their fins are in high demand in Asia for use in shark fin soup. Their hides are used on a limited basis for manufacturing leather goods and their livers are used to extract oil. They are not known to be aggressive towards humans. They are actively pursued by recreational anglers as a game fish. They are utilized by the aquarium trade at modest levels.