Spinner Shark: Carcharhinus brevipinna

Family: Carcharhinidae
Common name(s)

Spinner Shark.

Identification

Body relatively slender. Snout long, pointed, and somewhat laterally depressed. First dorsal fin origin level with (or slightly posterior to) free rear tip of pectoral fin. Second dorsal origin over anal fin origin. No interdorsal ridge. Dorsal colouration grey-brown or bronzy. Subtle light band on flank. Distinct black tips on most fins in adults; especially obvious and well defined on lower caudal lobe. Black fin tips may be absent or indistinct in juveniles.

Size

Maximum length possibly 278cm. Size at birth 58-65cm.

Habitat

Warm-temperate and tropical coastlines. From close inshore to the edge of the continental shelf. Found from the surface to at least 75m depth.

Distribution

The spinner shark has a very wide, almost circumtropical distribution, but it has not been recorded in the eastern Pacific. In the western Atlantic, it is present from North Carolina to Venezuela including the Gulf of Mexico. And from northern Brazil to northern Argentina.
It is a seasonally abundant species in South Africa and is present around much of the African continent including Madagascar and islands further north. It is also present across the northern edge of the Indian Ocean, throughout Southeast Asia, northern Australia, and southern Japan.

Conservation Status

NEAR THREATENED

In the northwest Atlantic the spinner shark is part of the recreational shark fishery and is one of a suite of carcharhinids targeted by the directed commercial fishery operating along the southeast coast from North Carolina to Florida and throughout the Gulf of Mexico. It is a common component of the commercial catch in the north-central Gulf of Mexico, but is less often caught in the fisheries along the eastern seaboard of the United States. As with most carcharhinid species, spinner shark meat is sold under the name “Blacktip Shark” because of wide consumer preference for the product. It is a constituent of the substantial Mexican Gulf of Mexico shark catch. Probably it is represented in the shark catches in most areas within its range, but owing to confusion with the Blacktip Shark, it is likely that the species is not recorded in landings data. Fins are dried and shipped to the Far East where they are used in shark fin soup. In some areas the hides are likely to be utilized in preparing leather and the livers are used to extract oil.

Citations and References
Burgess, G.H. 2009. Carcharhinus brevipinnaThe IUCN Red List of Threatened Species 2009: e.T39368A10182758. https://dx.doi.org/10.2305/IUCN.UK.2009-2.RLTS.T39368A10182758.en. Downloaded on 24 September 2020.

Reproduction

A viviparous species with yolk-sac placenta. 3-15 pups per litter. Gestation is approximately 12 months. In North America, mating occurs in June, and birthing in May.

Diet

Diet mainly consists of small schooling fishes. Spinner sharks in South Africa predate heavily on pilchards (Sardinops sagax). Spinners are also known to eat stingrays and cephalopods.

Behavior

Spinner sharks are named for their habit of performing aerial leaps and twists when chasing prey. They do not appear to do this in every region so it may depend on specific prey species to warrant this gross expenditure of energy. It has also been suggested that their leaps are performed to rid themselves of parasites.

Spinners congregate in large numbers in the South African winter months to feed on migrating sardines that are corralled into bait balls by pods of common dolphins. Although there is no evidence that the sharks consciously cooperate with the dolphins to corral the fish, they may inadvertently help to pin the bait at the surface by attacking the bait ball from below.

Reaction to divers

Somewhat shy around scuba divers. When focused on feeding, spinners will allow a very close approach but they will abandon a bait ball if divers pursue them too aggressively.

Diving logistics

Spinner sharks are commonly seen during the Sardine Run in South Africa. I have dove on bait balls that were almost exclusively being preyed upon by spinner sharks, and bait balls that had other shark species but no spinners at all, so it is not guaranteed that you will encounter this species during any particular encounter even if the shark action is good.
Apparently, spinner sharks also show up in large numbers during bait fish migrations in Western Australia but the ‘Australian Run’ is far less predictable.

I also ran into a few spinner sharks under an oil rig in the Gulf of Mexico while snorkeling with a large aggregation of baited silky sharks. Although they did not approach closely enough for good images, they seemed comfortable circling slowly about 10m below the silkies.

Similar species

Blacktip Shark Distinguished by its stockier body, more anterior first dorsal fin (origin situated over the pectoral axil), a bolder flank stripe, and some unmarked fins.