Australian blacktip shark
A requiem shark endemic to northern and eastern Australia.
The Australian blacktip shark (Carcharhinus tilstoni) is a requiem shark found only in the waters off northern and eastern Australia. It looks almost exactly like the common blacktip shark (C. limbatus), and the only reliable ways to tell them apart are by counting vertebrae—this species has fewer—or by using genetic tests. It is one of the sharks most frequently caught by commercial fisheries in northern Australia, where its meat is sold as "flake."
This shark was first described in 1950 by Australian ichthyologist Gilbert Percy Whitley, who named it *Galeolamna pleurotaenia tilstoni* after Richard Tilston, an assistant surgeon at Port Essington in the Northern Territory. The type specimen—a 1.5-meter-long female—was caught at Van Cloon Reef in Joseph Bonaparte Gulf. Later scientists moved it into the genus *Carcharhinus*. It is also known as the blacktip whaler, Tilston's whaler shark, or Whitley's blacktip shark. For years after its description, it was considered the same species as the common blacktip, but research in the 1980s using morphology and life history data, followed by allozyme studies by Shane Lavery and James Shaklee, confirmed it as a separate species. Genetic studies show that both blacktip species, along with the graceful shark (*C. amblyrhynchoides*) and the smoothtooth blacktip shark (*C. leiodon*), form a close evolutionary group, though the exact relationships among them remain unclear.
Physically, the Australian blacktip has a moderately stout, spindle-shaped body and a long, pointed snout. Its nostrils have slightly enlarged triangular flaps on their front rims, and its large, round eyes have nictitating membranes. The corners of its mouth have barely visible furrows. It has 32 to 35 upper teeth and 29 to 31 lower teeth; the upper teeth are slender and upright with fine serrations that get coarser near the base, while the lower teeth are narrower and more finely serrated. Its five pairs of gill slits are long. The pectoral fins are long, narrow, and sickle-shaped with pointed tips. The first dorsal fin is large and also sickle-shaped, starting above or just behind the rear of the pectoral fins. The second dorsal fin is moderately tall and sits roughly opposite the anal fin. There is no ridge between the dorsal fins. A crescent-shaped notch appears on the tail stalk just before the upper tail fin.
Quick Facts
- Genus
- Carcharhinus
- Species
- tilstoni
Facts from the source article.
Lore & Background
The Australian blacktip shark was described by Australian ichthyologist Gilbert Percy Whitley in a 1950 issue of the scientific journal Western Australian Naturalist. He named it Galeolamna pleurotaenia tilstoni in honor of Richard Tilston, assistant surgeon at Port Essington, Northern Territory. The type specimen is a 1.5 m (4.9 ft) long female caught from Van Cloon Reef in Joseph Bonaparte Gulf. Later authors have regarded Galeolamna as a synonym of the genus Carcharhinus. After Whitley's initial description, C. tilstoni was generally regarded as synonymous with C. limbatus, but in the 1980s additional morphological and life history data favored its recognition as a separate species, eventually confirmed by allozyme studies performed by Shane Lavery and James Shaklee.
Physically, the Australian blacktip shark has a moderately robust, spindle-shaped body and a long, pointed snout. It is bronze above and whitish below, with black tips on some or all fins. It typically reaches 1.5–1.8 m (4.9–5.9 ft) in length. This species inhabits the continental shelf from Thevenard Island in Western Australia to Sydney in New South Wales, co-occurring with the common blacktip shark. It forms large groups segregated by size and sex, preys mainly on teleost fishes, and exhibits viviparity with a well-defined annual reproductive cycle. Hybrids between the Australian blacktip shark and the common blacktip shark have been discovered along the eastern coast of Australia, the first confirmed case of hybridization among cartilaginous fishes.
Reader's Guide
The Australian blacktip shark is one of the most economically important sharks off northern Australia. It was historically fished for its meat and fins by a Taiwanese gillnet fishery that began operating off northern Australia in 1974, with the annual catch initially averaging around 25,000 tons (live weight), approximately 70% of which consisted of Australian blacktip sharks, spottail sharks, and longtail tuna. Following the establishment of the Australian Fishing Zone (AFZ) in November 1979, the Australian government progressively excluded Taiwanese gillnet vessels from large portions of Australian waters and imposed fishing quotas. The species continues to be caught by the Australian Northern Shark Fishery. As current fishing levels are not thought to threaten this shark's population, the International Union for Conservation of Nature (IUCN) has assessed it as Least Concern. Its meat is sold as 'flake', and it is also valued for its fins.
Did You Know?
- The Australian blacktip shark is virtually identical in appearance to the common blacktip shark, differing only in vertebra number and genetic markers.
- It was originally described as Galeolamna pleurotaenia tilstoni by Gilbert Percy Whitley in 1950.
- Females bear litters of one to six pups after a 10-month gestation period, with mating occurring in February and March.
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