Blacktip Shark, Oceanic Blacktip Shark.
Snout long and pointed. First dorsal fin high. First dorsal origin approx. midway between pectoral fin insertion and free rear tip. Second dorsal origin level with anal fin origin. No interdorsal ridge. Dorsal coloration grey to grey-brown with a well defined pale band on flank. First dorsal, second dorsal, pectoral fins, and lower caudal lobe usually have a dusky posterior margin, sometimes with a black tip. Anal fin generally pale in blacktips from the Atlantic, black-tipped in sharks from the Pacific.
For many years, researchers have suspected that there are multiple species of blacktip sharks separated by region. Analysis by Keeny and Heist in 2006 revealed that there are two geographically distinct lineages; a western Atlantic, Gulf of Mexico and Caribbean clade, and an eastern Atlantic, Indian Ocean and Pacific Ocean clade. In Jose Castro’s Sharks of North America, he reinforces this point, stating that Western Atlantic blacktips he has examined differ significantly from Pacific and Indian Ocean specimens in numerous traits such as size, markings, age at maturity, and litter size.
Maximum length 255cm. Size at birth 38-72cm.
Blacktip sharks inhabit shallow coastal waters and offshore waters but they remain near the surface over deep water. They will enter brackish estuaries but do not venture into fresh water.
The blacktip shark has an extremely cosmopolitan distribution in tropical and sub-tropical nearshore environments.
In the western North Atlantic this species has long been important in the recreational fishery and now is a primary target of the directed commercial fishery along the southeast coast from South Carolina to Florida and throughout the Gulf of Mexico (Branstetter and Burgess 1996, 1997). It is the second most important commercially landed species in that region after the Sandbar Shark (Carcharhinus plumbeus) and its meat is considered superior to the latter species. In the USA, Blacktip Shark other carcharhinid meat is often sold under the name “Blacktip Shark” because of wide consumer preference for the product. It is a significant constituent of the substantial Mexican shark catch, from both Atlantic and Pacific coasts. Elsewhere, it is the most commonly caught species in the large Indian fishery (Hanfee 1996), occasionally caught in the Mediterranean Sea driftnet fishery (Walker et al. 2005), and surely constitutes a sizeable portion of the catch in smaller scale and artisanal fisheries throughout the northern Indian Ocean and South China Sea. In Australia, it represents a minor component of the shark catch in northern Australia (Last and Stevens 1994). Blacktip Shark meat is primarily consumed locally and fins are dried and shipped to the Far East where they are used in preparing shark-fin soup. In some areas the hides are utilised in preparing leather and the livers are used to extract oil.
Citations and References
Burgess, H. G. & Branstetter, S. 2009. Carcharhinus limbatus. The IUCN Red List of Threatened Species 2009: e.T3851A10124862. https://dx.doi.org/10.2305/IUCN.UK.2009-2.RLTS.T3851A10124862.en. Downloaded on 27 September 2020.
A viviparous species with yolk-sac placenta. 1-10 pups per litter. Gestation (in the Atlantic clade) is approximately 11 months. Mating occurs biannually.
In the western Atlantic, blacktips feed mostly on menhaden and other small schooling fishes. They are known to follow shrimp trawlers and feed on discarded bycatch. They will also consume cephalopods and. crustaceans.
A migratory species. In the western Atlantic, blacktips migrate north to give birth in nursery grounds in the Carolinas during the warmer months, returning before water temperatures drop below 21ºC in the fall.
Blacktips are known to segregate by sex, with females entering shallower water than males. During their migrations, they form enormous loose schools. Aerial footage of these events have been used by numerous Florida news services to sensationalize the threat of sharks in Florida waters.
Blacktips are famous for their aerial displays during which they leap into the air. They do this inadvertently while pursuing fast moving bait fish.
Reaction to divers
Usually quite shy and difficult to approach unless a natural feeding event is in progress such as the Sardine Run. Bold in baited situations but not especially aggressive towards divers.
Blacktip sharks are found in virtually every corner of the tropics and are sighted quite regularly by divers at numerous locations.
Probably the best place in the world to encounter them at close quarters is during one of the baited dives at Aliwal Shoal. Officially, these are pitched as ‘tiger shark encounters’ but the tigers can be a bit elusive. When I was there, we did see a tiger or two but they were quite shy and did not approach the bait. After many trips to Tiger Beach, I found the blacktip encounters much more rewarding than the occasional glimpse of a tiger. The blacktips at Aliwal are extremely comfortable around divers, making endless close passes that lead to amazing photographic opportunities.
Also in South Africa, blacktip sharks are often seen on the Sardine Run but usually in smaller numbers than spinner sharks, bronze whalers and duskies.
In French Polynesia, I have seen blacktips in the passes of the Tuamotu Archipelago mixed in with hundreds of grey reef sharks but they always stayed at distance.
I have also seen them around Nuka Hiva in the Marquesas Archipelago. On the reefs there, they were easier to approach. On the south side of Nuku Hiva in Taioha’e Bay, blacktip sharks come right up to the dock to scavenge on fish scraps thrown discarded by fishermen. One morning I decided to slip while the fishermen were cleaning their catch. The visibility was extremely poor and I was immediately and repeatedly bumped by sharks until I exited the water.
The Blacktip Shark Complex As mentioned in the species description, blacktip sharks likely represent a complex of multiple closely-related species that have yet to be separated.
Australian Blacktip Shark An extremely similar species that was until recently considered synonymous with the blacktip shark. Identification in the field is impossible, although this species is somewhat smaller and with less vertebrae, so mature animals may appear smaller than normal.