Carcharias taurus (East coast of Australia subpopulation)http://dx.doi.org/10.2305/IUCN.UK.2003.RLTS.T44070A10854830.en
|Scientific Name:||Carcharias taurus (East coast of Australia subpopulation)|
|Species Authority:||Rafinesque, 1810|
|Taxonomic Notes:||Synonyms = Odontaspis taurus (Rafinesque, 1810); Eugomphodus taurus (Rafinesque, 1810).|
|Red List Category & Criteria:||Critically Endangered A2abcd+3cd+4abcd ver 3.1|
|Assessor(s):||Pollard, D., Gordon, I., Williams, S., Flaherty, A. & McAuley, R.|
|Reviewer(s):||Shark Specialist Group Australia & Oceania Regional Workshop, March 2003, participants (Shark Red List Authority)|
Numbers of Carcharias taurus in inshore waters of New South Wales (NSW) and southern Queensland (QLD) declined dramatically throughout the 1960s and 1970s due to the combined effects of targeted spearfishing, incidental capture by commercial and recreational fishing and beach protective shark meshing. Numbers in NSW are very low, probably numbering less than 500 and possibly as low as 300. The Critically Endangered assessment is assigned due to observed declines in the numbers of sharks at aggregation sites, a reduction in the number of known aggregation sites and dramatic declines in catch rates in beach protective meshing programs. Although protected in NSW since 1984, they are still subject to incidental capture and there appears to be little or no recruitment at sites where populations have become locally extinct.
|Range Description:||Because Carcharias taurus is extremely rare in the Northern Territory and South Australia, there is likely to be almost no genetic exchange between sharks on the east and west coasts and, for the purposes of this assessment, the Australian subpopulation is considered to consist of two subpopulations: the New South Wales (east coast) subpopulation, and the Western Australia (west coast) subpopulation. Information for the New South Wales subpopulation follows:
The grey nurse shark is a migratory species that is known to move north and south between particular sites along the east coast of Australia. When not migrating, these sharks aggregate in or near deep sandy-bottomed gutters or in rocky caves around inshore rocky reefs and islands at depths between 15 and 40 metres (Otway and Parker 2000). Depending on the time of year, both mature and juvenile grey nurse sharks may be found at aggregation sites in southern Queensland and New South Wales. The results of diver surveys concluded that grey nurse sharks were no longer found at many of the sites that they were known to previously use.
Native:Australia (New South Wales, Queensland)
|FAO Marine Fishing Areas:||
Pacific – southwest; Pacific – western central
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||The east coast subpopulation has been estimated to possibly consist of as few as 500 individuals (Otway and Parker 2000) and there are concerns that this subpopulation has fallen to such critically low numbers that individual animals may be failing to find mates.|
|Current Population Trend:||Decreasing|
|Habitat and Ecology:||
Carcharias taurus generally occurs in warm-temperate and sub-tropical waters, ranging from the surf zone and shallow bays to approximately 200 m depth on the outer continental shelf. The species is most usually found on or near the bottom in reef areas but may occasionally occur in midwater or at the surface (Compagno 1984). In NSW and southern Queensland, C. taurus is most frequently sighted in or near sandy-bottomed gutters or in rocky caves, often around inshore rocky reefs and islands at depths of between 15 and 25 m (Pollard et al. 1996, Otway and Parker 1999).
Embryonic oviphagy and intra-uterine cannibalism occurs in this species and only two large pups are produced per litter every second year. As a result, annual rates of population increase are very low, greatly reducing its ability to sustain fishing pressure. Maximum size attained is 220 to 270 cm total length (TL) (males) and 300 to 320 cm TL (females). Age at maturity is 6 to 7 years (males) and 9 to 10 years (females). Female k = 0.11, Male k = 0.16 (Goldman 2002).
Currently the main threatening processes in Australian waters would appear to be commercial and recreational fishing (including shark control programs in NSW and QLD), in which this species is taken as a bycatch. It has also been suggested that excessive dive tourism activities (i.e., 'shark diving') may also have the potential to adversely impact upon populations of the grey nurse shark. Refer to the Recovery Plan for the Grey Nurse Shark (Carcharias taurus) in Australia (Environment Australia 2002) for a fuller description of threats facing grey nurse sharks in Australian waters.
Grey nurse sharks are no longer found in significant numbers at several sites on the East Coast of NSW where they used to be dominant during the 1950s and 1960s. These sites include Brush Island, Jervis Bay and Long Reef, where in the past (1950/60s) aggregations of 40 plus could be observed. However, a recent NSW Fisheries study found that they no longer aggregate at such locations. Numbers of grey nurse sharks in NSW were found to be unexpectedly low, probably numbering less than 500 and possibly as low as 300. There is concern that the east coast subpopulation is suffering from depensation having fallen to such critically low numbers that individual animals may now be failing to find mates.
During the early 1950s up to 36 grey nurse sharks per year were captured by shark control nets in NSW. However, by the 1980s this number had decreased to three or less per year, and over the last decade (up to 2000) only three grey nurse sharks were caught. The declining catch rate has continued despite increased meshing effort over this period as more beaches were included in the beach protection program. A similar trend was observed in data from the Queensland beach protection program, where grey nurse shark captures decreased from an average of nine sharks per year between 1962 and 1972, to slightly over two sharks per year (Reid and Krogh 1992).
Although grey nurse sharks have been protected in NSW since 1984, they are still subject to incidental capture by commercial and recreational fishers, and in the ongoing protective beach meshing programs. In particular, vessels targeting wobbegong sharks (Orectolobus spp.) in the NSW Trap and Line Fishery have a significant bycatch of this species (Fletcher and McVea 2000). In the 1998-2001 NSW diver survey, between 5% and 7% of observed grey nurse sharks had wobbegong setline and other line fishing hooks embedded in their jaws (Otway and Parker 2000). There also appears to be little or no recruitment at sites where populations have become locally extinct (D. Pollard and I. Gordon, pers. comms 2003).
Illegal finning, eco-tourism and trade for aquarium displays may pose additional threats to the recovery of grey nurse sharks in NSW and southern Queensland.
Protection Status in Australia
- Protected Species in Commonwealth waters under the EPBC Act, 1999: East Coast Subpopulation - Critically Endangered (2002).
- Listed as a Vulnerable Species in NSW waters under the Fisheries Management Act, 1994 (since 1999)·
- Listed as a Vulnerable Species in Victorian waters under the Fisheries Act 1995·
- Protected Species in NSW waters under the Fisheries Management Act, 1994 (since November 1984)·
- Protected Species in Tasmanian waters under the Fisheries Regulations, 1996 (since 1998)·
- Protected Species in Queensland waters under the Fisheries Act, 1994 (Fisheries Regulation 1995) (since 1997).
- A National Recovery Plan for the Grey Nurse Shark (Carcharias taurus) in Australia was adopted for implementation by the Minister for Environment and Heritage June 2002.
- A draft Recovery Plan for Grey Nurse Shark has been developed for New South Wales.
Proposed Conservation Measures
Conservation measures can been found in the National Recovery Plan for the Grey Nurse Shark (Carcharias taurus) in Australia (Environment Australia 2002). The overall conservation objective is to increase Grey Nurse Shark numbers in Australian waters to a level that will see the species removed from the IUCN Red List.
Other conservation measures
Management measures have been developed for the critical habitat site identified at Pimpernel Rock in northern NSW. Details on management arrangements can be referred to in the Solitary Islands Marine Reserve (Commonwealth Waters) Management Plan Environment Australia, 2001 and the zoning plan for the Solitary Islands Marine Park - Marine Parks Authority, NSW, adopted 1 August 2002 (see Marine Parks Authority, New South Wales).
|Citation:||Pollard, D., Gordon, I., Williams, S., Flaherty, A. & McAuley, R. 2003. Carcharias taurus (East coast of Australia subpopulation). The IUCN Red List of Threatened Species 2003: e.T44070A10854830. http://dx.doi.org/10.2305/IUCN.UK.2003.RLTS.T44070A10854830.en . Downloaded on 06 October 2015.|