Carcharhinus sorrah

Taxonomy

Assessment Information

Geographic Range

Population

Habitat and Ecology

Threats

Conservation Actions

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Taxonomy [top]

Kingdom	Phylum	Class	Order	Family
ANIMALIA	CHORDATA	CHONDRICHTHYES	CARCHARHINIFORMES	CARCHARHINIDAE

Scientific Name:

Carcharhinus sorrah

Species Authority:

(Müller & Henle, 1839)

Common Name/s:

English

–

Spottail Shark

Synonym/s:

Carcharias sorrah Müller & Henle, 1839

Taxonomic Notes:

A separate species may exist in Southeast Asia, but this needs a much more detailed investigation.

Assessment Information [top]

Red List Category & Criteria:	Near Threatened ver 3.1
Year Published:	2009
Assessor/s:	Pillans, R., Stevens, J.D. & White, W.T.
Reviewer/s:	Valenti, S.V. & Fowler, S.L. (Shark Red List Authority)
Justification: Spottail Shark (Carcharhinus sorrah) is a tropical Indo-Pacific species, recorded patchily from South Africa to southern China, and common on continental and insular shelves close inshore (20?50 m), occurring out to 140 m. This is among the most productive of sharks. Catch per unit effort (CPUE) data for sharks caught in the Taiwanese gillnet fishery off northern Australia (now closed), of which Spottail Shark comprised about 20%, together with fast growth rates, early maturity and relatively high fecundity, suggest that this species is more resilient to exploitation than most other shark species. Although this species is more productive than many other carcharhinids, it is heavily exploited throughout a larger proportion of its range and the nursery areas used by their juveniles are extremely heavily fished and also affected by habitat degradation and possibly pollution. Currently, annual landings of sharks in northern Australia (mainly Australian Blacktip Shark (C. tilstoni) and Spottail Shark) 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 Australian population of Spottail Shark, and the species is assessed as Least Concern in these waters. Intensive unmanaged and unreported inshore fisheries are, however, taking this species (and other carcharhinids) in other parts of its range (certainly in Indonesia, other areas of Southeast Asia and likely elsewhere), where similar population declines to those previously observed in Australian waters have probably occurred and are likely to continue unchecked. Catches observed in Indonesia during a five year study were relatively high, however probably not as common as would be expected, especially compared to the populations off northern Australia. Tagging data from Australia suggest that stocks of C. sorrah in areas of intensive fishing are susceptible to local population decline. Recent stock discrimination work has demonstrated that Indonesian and Australian stocks are discrete. Thus, population declines in Southeast Asia are unlikely directly to affect populations in Australian waters. Increased IUU fishing in Australian waters is a major and possibly increasing concern for this stock. The Spottail Shark is thus assessed as Near Threatened globally based on the extreme high fishing pressure throughout most of its range and its inferred population declines on a global scale (close to meeting the criteria for VU A2bd+A3bd).

Geographic Range [top]

Range Description:	This species is wide-ranging throughout the tropical Indo-West Pacific, from South Africa and Mozambique, through the Indian Ocean and Southeast Asia, to Australia (Compagno in prep, White et al. 2006).
Countries:	Native: Australia (New South Wales, Northern Territory, Queensland, Western Australia); China; Egypt; Eritrea; India; Indonesia; Madagascar; Malaysia; Mauritius; Mozambique; Pakistan; Philippines; Saudi Arabia; Seychelles; Singapore; Solomon Islands (Santa Cruz Is., South Solomons); Somalia; South Africa; Sri Lanka; Sudan; Taiwan, Province of China; Thailand; Viet Nam; Yemen
FAO Marine Fishing Areas:	Native: Indian Ocean – eastern; Indian Ocean – western; Pacific – western central; Pacific – northwest
Range Map:	Click here to open the map viewer and explore range.

Population [top]

Population:	Population genetic studies of Indonesian and Australian populations have shown that they are different stocks (Queensland Department of Primary Industries and Fisheries, unpubl. data). Genetic evidence suggested that this species forms one population in Australian waters (Lavery and Shacklee 1989). Tagging studies off Northern Australia have shown that 49% of sharks were recaptured within 50 km of the tagging site, however one shark was captured 1,116 km away (Stevens et al. 2000). These authors also showed that most animals moved along the coastline. Data from this study suggests that although there was sufficient movement to prevent stock differentiation, the degree of movement was not great enough to prevent a reduction in local populations as a result of heavy fishing pressure. This conclusion contradicts those of Lavery and Shacklee (1989) who had 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. Further stock discrimination and assessment throughout its whole range is required. Variation in vertebral counts and litter sizes between C. sorrah in the Red Sea and southwestern Indian Ocean may suggest relatively isolated populations there, but this requires confirmation (Compagno in prep). Very common off northern Australia. Relatively common off Indonesia but possibly not as common as would be expected (W. White pers. obs).
Population Trend:	Unknown

Population:

Population genetic studies of Indonesian and Australian populations have shown that they are different stocks (Queensland Department of Primary Industries and Fisheries, unpubl. data). Genetic evidence suggested that this species forms one population in Australian waters (Lavery and Shacklee 1989). Tagging studies off Northern Australia have shown that 49% of sharks were recaptured within 50 km of the tagging site, however one shark was captured 1,116 km away (Stevens et al. 2000). These authors also showed that most animals moved along the coastline. Data from this study suggests that although there was sufficient movement to prevent stock differentiation, the degree of movement was not great enough to prevent a reduction in local populations as a result of heavy fishing pressure. This conclusion contradicts those of Lavery and Shacklee (1989) who had 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.

Further stock discrimination and assessment throughout its whole range is required. Variation in vertebral counts and litter sizes between C. sorrah in the Red Sea and southwestern Indian Ocean may suggest relatively isolated populations there, but this requires confirmation (Compagno in prep).

Very common off northern Australia. Relatively common off Indonesia but possibly not as common as would be expected (W. White pers. obs).

Population Trend:

Unknown

Habitat and Ecology [top]

Habitat and Ecology:	A common inshore shark, on continental and insular shelves found from close inshore to a depth of at least 140 m (Compagno and Niem 1998e). Common over mud and sand bottom in depths between 20?50 m but also occurs near coral reefs. Occurs throughout the water column but mainly in midwater or near the surface (Last and Stevens 1994). Young prefer very shallow, inshore waters. Attains at least 160 cm total length (TL) and is viviparous with a yolk-sac placenta (White et al. 2006, Compagno in prep). In Australia, size at maturity 90 cm TL (males) and 95cm TL (females). Age at maturity is 2?3 years. Gestation period of 10 months and a reproductive periodicity of one year. Litter size ranges from 1?8 pups/litter (average three), with size at birth 50 cm TL. Growth rate of juveniles are 20 cm/year for the first year, declining to 5 cm/year when the sharks are about five years old (Stevens and Wiley 1986, Davenport and Stevens 1988). In Indonesia, size at maturity 112 cm TL (males), litter size 3?8 (average five), size at birth 52?55 cm TL in October (White 2007). In Bombay, birth occurs in spring (March-May) (Compagno in prep). Diet consists of bony fishes (e.g., Bonito and sea bass) and cephalopods (White et al. 2006).
Systems:	Marine

Habitat and Ecology:

A common inshore shark, on continental and insular shelves found from close inshore to a depth of at least 140 m (Compagno and Niem 1998e). Common over mud and sand bottom in depths between 20?50 m but also occurs near coral reefs. Occurs throughout the water column but mainly in midwater or near the surface (Last and Stevens 1994). Young prefer very shallow, inshore waters. Attains at least 160 cm total length (TL) and is viviparous with a yolk-sac placenta (White et al. 2006, Compagno in prep). In Australia, size at maturity 90 cm TL (males) and 95cm TL (females). Age at maturity is 2?3 years. Gestation period of 10 months and a reproductive periodicity of one year. Litter size ranges from 1?8 pups/litter (average three), with size at birth 50 cm TL. Growth rate of juveniles are 20 cm/year for the first year, declining to 5 cm/year when the sharks are about five years old (Stevens and Wiley 1986, Davenport and Stevens 1988). In Indonesia, size at maturity 112 cm TL (males), litter size 3?8 (average five), size at birth 52?55 cm TL in October (White 2007). In Bombay, birth occurs in spring (March-May) (Compagno in prep). Diet consists of bony fishes (e.g., Bonito and sea bass) and cephalopods (White et al. 2006).

Systems:

Marine

Threats [top]

Major Threat(s):	Regularly taken as utilized bycatch of longlines, gillnets, trawls and other line gear (Compagno in prep, White et al. 2006, SEAFDEC 2006). Inshore fisheries are generally intensive throughout this species? inshore range in Southeast Asia and in many parts of the Indian Ocean. Spottail Shark is captured as both a target species and as bycatch in northern Australian shark, finfish and prawn fisheries, although current catch rates are highly unlikely to threaten the Australian population. Historically, Spottail Shark contributed about 20% by number to the Taiwanese gillnet fishery that operated in Australian waters between 1979 and 1986 (Stevens and Davenport 1991). This fishery?s annual catch was about 7,000 t 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 and then increased to about 6 kg/km in 1986, (Stevens and Davenport 1991). Illegal, unreported and unregulated (IUU) fishing activities have greatly increased in northern Australian waters in recent years. Indonesian fishers are increasingly fishing illegally in this area, the majority of whom are targeting shark (although a few target reef fish and trepang) (AMFA 2007, Vince 2007). Spottail Shark is commonly caught in the Indonesian artisanal fisheries and marketed (White et al. 2006) but at a lower level than would have been expected for a typically very common species. Although this suggests a relatively low catch rate, there are no data on CPUE and it is therefore not possible to determine whether the low catches are due to small population size caused by overfishing. However, giving the extremely high level of fishing pressure in the Southeast Asian region and the problem of habitat degradation in inshore waters throughout much of its range (not Australia), this species is likely to be under great pressure. Nursery areas are extremely important for Spottail Shark, with juveniles inhabiting shallow inshore waters until they attain a larger size. These nursery areas are heavily fished in areas such as Indonesia and are also extremely susceptible to habitat degradation and even pollution, especially adjacent to riverine areas. This species is one of the dominant shark species in the landings of fisheries in Vietnam, Thailand, Indonesia and Malaysia. Most Spottail Sharks captured in these fisheries are immature (SEAFDEC 2006). Threats to the species? inshore habitat from fishing pressure and habitat degradation are also high in many areas within its range in the Indian Ocean, for example India, where inshore marine species are thought to be fully or overexploited, with extensive use of illegal mesh sizes reported (Flewwelling and Hosch 2006). India?s inshore fisheries are generally characterised by declining catch rates, declining recruitment and biomass, and a shift from regular landing patterns (Flewwelling and Hosch 2006). Sharks are heavily fished in the Red Sea and Gulf of Aden. Fisheries have experienced increased demand for sharks in recent years due to the shark fin trade and effort is increasing in traditional shark fisheries in many areas as a result (Henderson et al. 2007, Bonfil and Abdullah 2004). Spottail Shark was the third most important species of shark in traditional fishery landings of the Sultanate of Oman during a study from January 2002 to December 2003, although landings between areas were highly variable (Henderson et al. 2007).

Major Threat(s):

Regularly taken as utilized bycatch of longlines, gillnets, trawls and other line gear (Compagno in prep, White et al. 2006, SEAFDEC 2006). Inshore fisheries are generally intensive throughout this species? inshore range in Southeast Asia and in many parts of the Indian Ocean.

Spottail Shark is captured as both a target species and as bycatch in northern Australian shark, finfish and prawn fisheries, although current catch rates are highly unlikely to threaten the Australian population. Historically, Spottail Shark contributed about 20% by number to the Taiwanese gillnet fishery that operated in Australian waters between 1979 and 1986 (Stevens and Davenport 1991). This fishery?s annual catch was about 7,000 t 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 and then increased to about 6 kg/km in 1986, (Stevens and Davenport 1991). Illegal, unreported and unregulated (IUU) fishing activities have greatly increased in northern Australian waters in recent years. Indonesian fishers are increasingly fishing illegally in this area, the majority of whom are targeting shark (although a few target reef fish and trepang) (AMFA 2007, Vince 2007).

Spottail Shark is commonly caught in the Indonesian artisanal fisheries and marketed (White et al. 2006) but at a lower level than would have been expected for a typically very common species. Although this suggests a relatively low catch rate, there are no data on CPUE and it is therefore not possible to determine whether the low catches are due to small population size caused by overfishing. However, giving the extremely high level of fishing pressure in the Southeast Asian region and the problem of habitat degradation in inshore waters throughout much of its range (not Australia), this species is likely to be under great pressure. Nursery areas are extremely important for Spottail Shark, with juveniles inhabiting shallow inshore waters until they attain a larger size. These nursery areas are heavily fished in areas such as Indonesia and are also extremely susceptible to habitat degradation and even pollution, especially adjacent to riverine areas. This species is one of the dominant shark species in the landings of fisheries in Vietnam, Thailand, Indonesia and Malaysia. Most Spottail Sharks captured in these fisheries are immature (SEAFDEC 2006).

Threats to the species? inshore habitat from fishing pressure and habitat degradation are also high in many areas within its range in the Indian Ocean, for example India, where inshore marine species are thought to be fully or overexploited, with extensive use of illegal mesh sizes reported (Flewwelling and Hosch 2006). India?s inshore fisheries are generally characterised by declining catch rates, declining recruitment and biomass, and a shift from regular landing patterns (Flewwelling and Hosch 2006). Sharks are heavily fished in the Red Sea and Gulf of Aden. Fisheries have experienced increased demand for sharks in recent years due to the shark fin trade and effort is increasing in traditional shark fisheries in many areas as a result (Henderson et al. 2007, Bonfil and Abdullah 2004). Spottail Shark was the third most important species of shark in traditional fishery landings of the Sultanate of Oman during a study from January 2002 to December 2003, although landings between areas were highly variable (Henderson et al. 2007).

Conservation Actions [top]

Conservation Actions:	None in place through much of its range. Fisheries catching this species in northern Australia are relatively well managed and reporting of catches is good.

Conservation Actions:

None in place through much of its range. Fisheries catching this species in northern Australia are relatively well managed and reporting of catches is good.

Citation:	Pillans, R., Stevens, J.D. & White, W.T. 2009. Carcharhinus sorrah. In: IUCN 2011. IUCN Red List of Threatened Species. Version 2011.2. <www.iucnredlist.org>. Downloaded on 24 May 2012.
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