Family: Carcharhinidae – Requiem sharks
Common Name– Ground Sharks
Common Name– Requiem Sharks
Status: IUCN Red List LEAST CONCERN
Average Size and Length: The Australian Blacktip shark typically reaches 4.9–5.9 feet long. The maximum recorded length is 6.6 feet.
Average Weight: The maximum recorded weight is 115 pounds.
Teeth and Jaw: The Australian Blacktip shark has furrows at the corners of the mouth, but barely noticeable. There are 32–35 upper and 29–31 lower tooth rows; each upper tooth has a slender, upright cusp and fine serrations that become coarser near the base, while the lower teeth are narrower and more finely serrated.
Head: The Australian Blacktip shark has a long, pointed snout. They have nostrils with skin flaps, and large, circular eyes with nictitating membranes.
Denticles: The dermal denticles are rough and diamond-shaped and are placed closely together and slightly overlapping. Each has 5 to 7 (3 in juveniles) horizontal ridges leading to marginal teeth.
Tail: A falcate notch is present on the caudal peduncle just before the upper caudal fin origin. The caudal fin is asymmetrical, with a strong lower lobe and a longer upper lobe with a ventral notch near the tip.
Demographic, Distribution, Habitat, Environment and Range: It can be found over the continental shelf, and although it occupies the entire water column, it is most common close to the surface or in midwater. It has been reported from the intertidal zone to a depth of 490 feet deep, with larger sharks in deeper water. The Australian Blacktip shark mostly moves only short distances along the coastline and rarely enters offshore waters. There have been some accounts through tracking studies that report some sharks traveling as far as 838 miles.
The Australian Blacktip shark is found from Thevenard Island in Western Australia to Sydney in New South Wales.
The Australian Blacktip shark co-occurs with the common blacktip shark; the ratio between C. limbatus and C. tilstoni was once thought to be 1:300, but recent genetic studies have found it to be closer to 50:50. Genetic data suggest Australian blacktip sharks across northern Australia are all members of a single population.
Diet: The Australian Blacktip shark eats mainly teleost fishes, including ponyfishes, grunters, tunas, and herring. Around April, cephalopods become important. They will also eat other sharks on occasion such as Spottail sharks, Snaggletooth sharks, and Sharpnose sharks.
Their diets do shift with age. Smaller sharks feed on more bottom-dwelling fish, while larger individuals feed on proportionately more midwater fish and cephalopods.
Aesthetic Identification: The Australian Blacktip shark has a robust, spindle shaped body with 5 pairs of long gill slits. The Australian Blacktip shark is bronze above (gray when dead) and counter-shaded whitish below, with a pale stripe on the flanks. Some individuals have black tips on all fins, while others have unmarked pelvic and anal fins.
Physically, the Australian Blacktip shark can only reliably be distinguished from the common Blacktip shark by the number of vertebrae (174–182 total, 84–91 before the tail in C. tilstoni, 182–203 total, 94–102 before the tail in C. limbatus).
The long and narrow pectoral fins are falcate with pointed tips. The large first dorsal fin is also falcate and originates over or slightly behind the rear of the pectoral fin bases. The second dorsal fin is moderately tall and positioned about opposite the anal fin. There is no midline ridge between the dorsal fins.
Biology and Reproduction: Known parasites of the Australian Blacktip shark include the tapeworms Fossobothrium perplexum and Platybothrium sp., and the copepod Perissopus dentatus.
Hybrids between the Australian Blacktip shark and the common Blacktip shark, comprising both F1 and backcrossed individuals, have been discovered all along the eastern coast of Australia. However, there is no evidence the species are merging.
The Australian Blacktip shark is viviparous. Females have litters of 1 to 6 pups (but usually 3) every year. Mating takes place in February and March, with the females storing the sperm until ovulation in March and April. After a gestation period of 10 months, the young are born around January of the following year.
Nursery areas for near-term females are shallow and coastal like Cleveland Bay in northern Queensland, to give birth, but exist all throughout. Newborns are around 24 inches long. They grow fast at first then slows down per year by age 5.
Both sexes reach sexual maturity at 3 to 4 years of age, at lengths of around 3.6 and 3.9 feet for males and females. The maximum lifespan is estimated to be 20 years.
Australian Blacktip Shark Future and Conservation: The Australian blacktip shark has also been targeted by Australian commercial gillnetters and longliners in the Northern Shark Fishery. It is additionally caught incidentally by other commercial fisheries targeting bony fishes or prawns.
The northern Australian shark catch is estimated to be between 100 and 900 tons (live weight) annually, of which most are Australian Blacktip and Spottail sharks.
The meat of this species is sold in Australia as “flake”, though it may contain high concentrations of mercury. The fins are exported to Asia, while the cartilage, liver oil, and skin may also be used.
Australian Blacktip Shark Recorded Attacks on Humans: Not a threat or danger to humans.