Spinner Shark, Carcharhinus brevipinna
Spinner Shark, Carcharhinus brevipinna. Fish caught from coastal waters off Sebastian, Florida, July 2021. Length: 62 cm (2 feet 0 inches). Catch, photograph and identification courtesy of Ben Cantrell, Sebastian, Florida.
Spinner Shark, Carcharhinus brevipinna. Fish caught from coastal waters off Galveston, Texas, July 2020. Length: 79 cm (2 feet 7 inches). Catch, photograph and identification courtesy of Eli (obsessiveangling.wordpress.com).
The Spinner Shark, Carcharhinus brevipinna, is a member of the Requiem Shark or Carcharhinidae Family, and in Mexico as tiburón curro. They are named from their habit of making vertical spinning breaches up to 20-feet in the air, a feeding technique whereby they spin through schools of small fish with an open mouth and then break the surface. 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 Spinner Shark has a slender streamlined body. They are gray-bronze dorsally transitioning to white ventrally with a prominent white band on their sides. Their adults have anal fin, lower caudal fin lobe, dorsal fins and the undersides of the pectoral fins tipped in black or dark gray. Juveniles have unmarked fins. Their head has a long, narrow, point snout that is longer than the width of the mouth with small, circular eyes and their mouth is equipped with 30 to 36 rows of narrow-cusped finely serrated teeth on the upper jaw, 28 to 34 rows of narrow-cusped non-serrated teeth on the lower jaw, and two symphysial teeth on the upper jaw and one on the lower, and prominent forward pointed furrows at the corners and they have five pairs long gill slits. The caudal fin is slender, strongly asymmetrical with a well-developed lower lobe, and an undulated ridge along the dorsal surface of the top lobe, a notch under the tip of that lobe and a narrowly rounded tip; the first dorsal fin is small with a rounded apex and a short rear tip and originates over the free tips of the pectoral fins; the second dorsal fin is moderately large with a short rear tip; and, the pectoral fins are short, narrow and falcate with narrow pointed or rounded tips. They do not have an interdorsal ridge (a key to the identification). The body is densely covered with diamond-shaped dermal denticles with seven shallow horizontal ridges.
The Spinner Shark is found in water temperate, subtropical and tropical waters from close to shore to offshore near the continental and insular shelfs. They are found from the surface to depths of 100 m (330 feet) and are common in shallow waters. The juveniles are born and stay in inshore waters for extended periods of time. They travel in large schools segregated by age and by sex. They are known to be highly migratory moving south in the winter seeking warmer waters and north in the spring for mating. The females remain close to shore year-round and males are pelagic and only present near-shore during mating season. They are known as an active, fast swimming shark, that is often seen leaping out the water, spinning during the pursuit of prey. They reach a maximum of 3.0 m (9 feet 10 inches) in length and 90 kg (198 lbs) in weight. As of March 31, 2023, the International Game Fish Association world record for weight stood at 94.6 kg (208 lbs 9 oz) with the fish caught in coastal waters off Port Aransas, Texas in December 2009. They feed in large schools on small schooling fish such as anchovies, herrings, menhadens, and sardines, and many other bony fish and cephalopods. They are known to follow fishing trawlers consuming discarded by-catch. In turn they are preyed upon by larger sharks, especially the juvenile and subadult individuals. Reproduction is viviparous and involves a 2-year cycle with 11 to 15-month gestation periods and litter sizes of 3 to 15 pups. At birth, the pups measure between 60 cm (2 feet 0 inches) and 80 cm (2 feet 7 inches) in length and are immediately capable of caring for themselves. Juveniles inhabit shallow coastal waters for up to two years to avoid predation and seek food. They are relatively fast growers and mature sooner than their congeners but they do not reproduce until they are 12 to 14 years old. They have lifespans of up to twenty years.
The Spinner Shark is a resident of Mexican waters of the Atlantic Ocean but is limited to the southwest portions of Gulf of Mexico from Tampico, Tamaulipas to the northern coast of the Yucatán Peninsula.
The Spinner Sharks are most likely confused with the Blacktip Shark, Carcharhinus limbatus (smaller in stature; larger and broader upper teeth, dorsal fin further back on the body and slightly falcate, adults lack a black tipped anal fin).
From a conservation perspective the Spinner Shark is currently classified as VULNERABLE. Accurate population assessments has been difficult since they are easily and often confused with the Blacktip Shark. Although widely distributed they are vulnerable to heavy fishing pressure and human-induced habitat destruction due to their inshore preferences. Only the Australian and United States governments currently manage this species imposing commercial quota and bag limits. They are an important recreational fish, known for their leaping abilities when feeding or hooked, and fished commercially in locations where they are abundant. Commercially they are caught primarily via longline and as a bycatch in the pelagic longline fishery. Their meat is considered to be excellent and sold as “Blacktip Shark”. In general, their meat is consumed locally and their fins are exported to Asia for use in shark fin soup, for their skin as leather and for vitamin production. They are not considered to be dangerous to humans.