Carcharhinus brevipinna

The spinner shark (Carcharhinus brevipinna) is a species of requiem shark, in the family Carcharhinidae, named for the spinning leaps it makes as a part of its feeding strategy. This species occurs in tropical and warm temperate waters worldwide, except for in the eastern Pacific Ocean. It is found from coastal to offshore habitats to a depth of 100 m (330 ft), though it prefers shallow water. The spinner shark resembles a larger version of the blacktip shark (C. limbatus), with a slender body, long snout, and black-marked fins. This species can be distinguished from the blacktip shark by the first dorsal fin, which has a different shape and is placed further back, and by the black tip on the anal fin (in adults only). It attains a maximum length of 3 m (9.8 ft). Spinner sharks are swift and gregarious predators that feed on a wide variety of small bony fishes and cephalopods. When feeding on schools of forage fish, they speed vertically through the school while spinning on their axis, erupting from the water at the end. Like other members of its family, the spinner shark is viviparous, with females bearing litters of three to 20 young every other year. The young are born in shallow nursery areas near the coast, and are relatively fast-growing. This species is not usually dangerous to humans, but may become belligerent when excited by food. Spinner sharks are valued by commercial fisheries across their range for their meat, fins, liver oil, and skin. They are also esteemed as strong fighters by recreational fishers. The International Union for Conservation of Nature has assessed this species as near threatened worldwide and vulnerable off the Southeastern United States. The spinner shark was originally described as Carcharias (Aprion) brevipinna by Johannes Peter Müller and Friedrich Gustav Jakob Henle in their 1839 Systematische Beschreibung der Plagiostomen, based on the mounted skin of a 79-cm-long specimen collected off Java. This species was subsequently moved to the genera Aprion, Squalus, and Aprionodon before being placed within the genus Carcharhinus. The tooth shape and coloration of this species varies significantly with age and between geographical regions, which caused much taxonomic confusion. Other common names include black-tipped shark, great blacktip shark, inkytail shark, large blacktip shark, long-nose grey shark, longnose grey whaler, and smoothfang shark. Based on similarities in morphology, tooth shape, and behavior, the closest relatives of the spinner shark were originally believed to be the blacktip shark and the graceful shark (C. amblyrhynchoides). However, this interpretation was not supported by Gavin Naylor's 1992 allozyme analysis, which suggested that these similarities are the product of convergent evolution and that the closest relative of the spinner shark is the copper shark (C. brachyurus). In a 2007 ribosomal DNA study, the spinner shark was found to be the most genetically divergent of all the requiem shark species examined save for the tiger shark (Galeocerdo cuvier), being less related to other Carcharhinus species than the lemon shark (Negaprion brevirostris). Some uncertainty exists in the distribution data for the spinner shark due to confusion with the blacktip shark. In the Western Atlantic Ocean, it occurs from North Carolina to the northern Gulf of Mexico, including the Bahamas and Cuba, and from southern Brazil to Argentina. In the Eastern Atlantic, it occurs from off North Africa to Namibia. In the Indian Ocean, it is found from South Africa and Madagascar, to the Red Sea and the Gulf of Aden, to India and nearby islands, to Java and Sumatra. In the Pacific Ocean, it occurs off Japan, Vietnam, Australia, and possibly the Philippines. Parasitological evidence suggests that Indian Ocean spinner sharks have passed through the Suez Canal into the Mediterranean Sea, becoming Lessepsian migrants. The spinner shark has been reported from the ocean surface to a depth of 100 m (330 ft), though it prefers water less than 30 m (98 ft) deep, and occupies all levels of the water column. This species may be found from coastal waters to well offshore, over continental and insular shelves. Juveniles have been known to enter bays, but avoid brackish conditions. The northwest Atlantic subpopulation is known to be migratory; in spring and summer, they are found in warm inshore waters, and in winter, they move south into deeper water. The average spinner shark is 2 m (6.6 ft) long and weighs 56 kg (123 lb); this species attains a maximum known length and weight of 3 m (9.8 ft) and 90 kg (200 lb). Indo-Pacific sharks are generally larger than those from the northwest Atlantic. This species has a slim, streamlined body with a distinctive, long, pointed snout. The eyes are small and circular. Prominent, forward-pointing furrows occur at the corners of the mouth. The tooth rows number 15–18 in each half of the upper jaw and 14–17 in each half of the lower jaw, with two and one tiny symphysial (central) teeth, respectively. The teeth have long, narrow central cusps and are finely serrated in the upper jaw and smooth in the lower jaw. The five pairs of gill slits are long. The first dorsal fin is relatively small and usually originates behind the free rear tip of the pectoral fins. No ridge exists between the first and second dorsal fins. The pectoral fins are moderately short, narrow, and falcate (sickle-shaped). The body is densely covered with diamond-shaped dermal denticles with seven (rarely five) shallow horizontal ridges. The coloration is gray above, sometimes with a bronze sheen, and white below, with a faint white band on the sides. Young individuals have unmarked fins; the tips of the second dorsal fin, pectoral fins, anal fin, and lower caudal fin lobe (and sometimes the other fins, as well) are black in larger individuals. The spinner shark differs from the blacktip shark in that its first dorsal fin is slightly more triangular in shape and is placed further back on the body. Adults can also be distinguished by the black tip on the anal fin.