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Carcharhinus tilstoni

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA CHONDRICHTHYES CARCHARHINIFORMES CARCHARHINIDAE

Scientific Name: Carcharhinus tilstoni
Species Authority: (Whitley, 1950)
Common Name(s):
English Australian Blacktip Shark, Blacktip Whaler
Synonym(s):
Carcharhinus limbatus (non Müller & Henle, 1839)

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2003
Date Assessed: 2003-04-30
Annotations:
Needs updating
Assessor(s): Pillans, R. & Stevens, J. (SSG Australia & Oceania Regional Workshop, March 2003)
Reviewer(s): Fowler, S. & Cavanagh, R.D. (Shark Red List Authority)
Justification:
A northern Australian continental shelf endemic occurring from close inshore to about 150 m. CPUE data for sharks in the Taiwanese gill net fishery (now closed) of which Carcharhinus tilstoni comprised about 40%, together with this species' fast growth rates, early maturity and relatively high fecundity suggests that it is more resilient to exploitation than many other shark species, and will already have recovered from depletion by this fishery in the 1980s. Currently, annual landings of sharks in Northern Australia (mainly C. tilstoni and C. sorrah) are significantly smaller than historical catches. Although there is a need to monitor catches in these fisheries, current catch rates are highly unlikely to threaten the population.

Geographic Range [top]

Range Description: Together with C. sorrah, this species is an important component of the Northern Australian commercial shark fishery. Data from Taiwanese gill netting between 1975 and 1978 showed highest catches in North Queensland, Torres Staight, Gulf of Papua, Gulf of Carpentaria and Inshore Arafura Sea. Average size of C. tilstoni captured in the Timor Sea were much smaller than the areas above, suggesting that C. tilstoni utilizes the inshore areas of the Timor sea as a nursery area. Often occurs in large aggregations. Size showed a sharp increase with increasing depth (Lyle 1987).
Countries:
Native:
Australia (Northern Territory, Queensland, Western Australia)
FAO Marine Fishing Areas:
Native:
Indian Ocean – eastern; Pacific – western central
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: Genetic evidence suggested that this species forms one population in Australian waters (Lavery and Shacklee 1989. Tagging studies off Northern Australia have shown that 60% of sharks were recaptured within 50 km of the tagging site, however one shark was captured 1,113 km away (Stevens et al. 2000). These authors also showed that most animals moved along the coast line. Data from this study suggested that although there was sufficient movement to prevent stock differentiation, the degree of movement was not great enough to prevent a reduction in local population as a result of heavy fishing pressure. This conclusion contradicted those of Lavery and Shacklee (1989) who concluded that local populations would be well buffered by immigration of sharks from other areas and that under high fishing pressure, total population size rather than local population size was likely to be the limiting factor affecting production.
Population Trend: Stable

Habitat and Ecology [top]

Habitat and Ecology: A viviparous species with a gestation period of 10 months. C. tilstoni reproduces annually, producing an average litter size of three (1-6). Size at birth is 60 cm total length (TL). Age at maturity is 3 to 4 years: males reach maturity at 110 cm TL, females at 115 cm TL. Maximum size is 200 m TL. Growth rates, Juveniles: 17 cm.y-¹ for the first year, declining to 8 to 10 cm per year when the sharks are about five years old (Davenport and Stevens 1988, Last and Stevens 1994, Stevens and Wiley 1986).
Systems: Marine

Threats [top]

Major Threat(s): Historically, C. tilstoni contributed to the Taiwanese gill net fishery that operated in Australian waters between 1979-1986 (Stevens and Davenport 1991). This fisheries annual catch was about 7,000 tonnes processed weight of shark, tuna and mackerel. Sharks comprised about 80% of the total catch with C. sorrah and C. tilstoni accounting for about 60% (20% and 40% respectively). CPUE of sharks declined from 11 kg/km in 1979 to 3 kg/km in 1984 then increased to about 6 kg/km in 1986 (the year this fishery ceased), (Stevens and Davenport 1991) suggesting a roughly 50% population depletion. There was an apparent decrease in the number of mature male and female C. tilstoni from 1981 to 1986 (Stevens and Davenport 1991). Data from this fishery between 1975-1978 showed the highest catches were in North Queensland, Torres Straight, Gulf of Papua, Gulf of Carpentaria and Inshore Arafura Sea.

Together with C. sorrah, this species is an important component of the Northern Australian commercial shark fishery. C. tilstoni is captured as both a target species and as bycatch in Northern Australian shark, finfish and prawn trawl fisheries. Annual landings of sharks in Northern Australia (mainly C. tilstoni and C. sorrah) are estimated at between 100 and 900 tonnes live weight and these catch rates are highly unlikely to threaten the population.

Citation: Pillans, R. & Stevens, J. (SSG Australia & Oceania Regional Workshop, March 2003) 2003. Carcharhinus tilstoni. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 01 October 2014.
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