Species Spotlight: Grey Nurse Shark
Common name: Grey Nurse Shark; Sand Tiger Shark
Scientific name: Carcharias taurus
Range: tropical and temperate waters in the Atlantic, Indian and Western Pacific Oceans
Conservation status: globally Vulnerable on the IUCN RedList, but the eastern Australia population is Critically Endangered
INFORMATION
The Grey Nurse Shark is one of three species in the Odontaspididae family (Last & Stevens, 2009). It is also known as the spotted ragged-tooth shark in South Africa and as the sand tiger shark in the northwest and southwest Atlantic (Pollard et al., 1996; Last & Stevens, 2009). The Grey Nurse Shark lives in shallow coastal waters in the Atlantic, Indian and Western Pacific Oceans (McGouther, 2021). They are a migratory species and tend to aggregate in or near deep sandy gutters or rock caves (Pollard et al., 2003). Grey Nurse Sharks are counter-shaded with a dark grey-brown upper body and a pale underside, meaning they are difficult to see from both above and below (McGouther, 2021). They can grow to a maximum length of 3.18 meters and a maximum weight of 190 kilograms (Pepperell, 1992). Grey Nurse Sharks survive on a diet comprised of a wide range of fish, other sharks, rats, squid, crabs and lobsters.
Like all sharks, the Grey Nurse Shark has the same five senses as humans, with the addition of electroreception as a sixth sense. Pores dotted along the underside of the Grey Nurse Shark's snout connect to an electricity-detecting organ (McGouther, 2021). This gives them the ability to detect and attack close-range prey without seeing them and allows them to navigate using the Earth's magnetic field (McGouther, 2021). Grey Nurse Sharks swallow air at the surface and hold it in their stomachs to enhance buoyancy, allowing them to glide easily above the ocean floor (McGouther, 2021). Grey Nurse Sharks are slow-moving and, despite their sharp, fang-like teeth, are not considered dangerous to people (McGouther, 2021).
THREATS AND CONSERVATION
The numbers of Grey Nurse Sharks observed in inshore waters of eastern Australia dropped dramatically during the 1960s and 1970s as a result of spearfishing, incidental capture and beach protection programs (Pollard et al., 2003). The east Australian population of Grey Nurse Sharks was listed as Critically Endangered in 2003 due to observed declines in shark numbers at aggregation sites, reduced numbers of known aggregation sites and dramatic decreases in catch rates in beach protective meshing programs (Pollard et al., 2003). The primary threats to this population include commercial and recreational fishing by-catch and shark control programs operated in New South Wales and Queensland (Pollard et al., 2003; Department of the Environment, 2014). Other threats include excessive dive tourism (i.e. shark diving), ecotourism, illegal finning and trade for aquarium displays (Pollard et al., 2003). The number of Grey Nurse Sharks along the east coast of Australia has dropped so low that individual sharks may now be failing to find mates (Pollard et al., 2003).
Despite being protected in New South Wales since 1984 and nationally since 1996, the Grey Nurse Shark continues to be adversely impacted by incidental capture and beach protection programs (Pollard et al., 2003; Department of the Environment, 2014). The Grey Nurse Shark is protected under Australia's Environment Protection and Biodiversity Conservation (EPBC) Act 1991. When a species is listed under the EPBC Act, it is subject to conservation advice, recovery plans, recovery teams and assessment and approval provisions. Under the Act's requirements, actions that have, or are likely to have, a significant impact on a listed threatened species are prohibited unless Ministerial approval is obtained (s 18, EPBC Act). The Australian government completed the first recovery plan created for the species under the EPBC Act in 2002. The second (and most recent plan) was created in 2014, despite the requirement for reviewed plans every five years. The objective of the current recovery plan is to assist the recovery of the species in the wild by improving population status and ensuring anthropogenic activities do not hinder this recovery (Department of the Environment, 2014).
Despite these protections, governments continue to take actions that actively endanger the Grey Nurse Shark. For example, in 2019, the New South Wales government announced that one of the ten critical habitats of the shark located along the State's coastline would be opened up to fishing in the Bateman's Bay Marine Park for six months of the year (Australia Marine Conservation Society, 2019). This decision was criticised by many for further exposing the already critically endangered species to more threats. State-sanctioned routine shark culls in the name of beach-goer protection is another ongoing threat faced by Grey Nurse Sharks in eastern Australia. Despite being abandoned in other states such as Western Australia, drumlines and nets are still used in 'beach protection programs' to the great detriment of many species, including the Grey Nurse Shark. Every year, hundreds of animals are killed in shark nets and drumlines, including threatened, vulnerable and endangered species that the government is obligated to protect (Australia Marine Conservation Society, n.d.). These programs have been heavily criticised for their negative effect on marine life and the lack of effectiveness in improving human safety (Gibbs et al., 2019).
REFERENCES
Australian Marine Conservation Society. (n.d.). Culling. Retrieved 10 July 2021, from https://sharkchampions.org.au/issue/culling/
Australian Marine Conservation Society. (2019). Critically Endangered Grey Nurse Shark Habitat Protection Slashed. Retrieved 10 July 2021, from https://www.marineconservation.org.au/critically-endangered-grey-nurse-shark-habitat-protection-slashed/
Department of the Environment. (2014). Recovery Plan for the Grey Nurse Shark. Australian Government.
Gibbs, L., Fetterplace, L., Rees, M., & Hanich, Q. (2019). Effects and effectiveness of lethal shark hazard management: The Shark Meshing (Bather Protection) Program, NSW, Australia. People And Nature, 2(1), 189-203. doi: 10.1002/pan3.10063.
Last, P., & Stevens, J. (2009). Sharks and rays of Australia. Cambridge, Mass.: Harvard University Press.
McGrouther, M. (2021). Greynurse Shark, Carcharias taurus Rafinesque, 1810. Retrieved 10 July 2021, from https://australian.museum/learn/animals/fishes/greynurse-shark-carcharias-taurus-rafinesque-1810/
Pepperell, J. (1992). Trends in the distribution, species composition and size of sharks caught by Gamefish Anglers off South-eastern Australia, 1961-90. Marine And Freshwater Research, 43(1), 213. doi: 10.1071/mf9920213
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. https://dx.doi.org/10.2305/IUCN.UK.2003.RLTS.T44070A10854830.en. Downloaded on 09 July 2021.
Pollard, D., Lincoln Smith, M., & Smith, A. (1996). The biology and conservation status of the grey nurse shark (Carcharias taurus Rafinesque 1810) in New South Wales, Australia. Aquatic Conservation: Marine And Freshwater Ecosystems, 6(1), 1-20. doi: 10.1002/(sici)1099-0755(199603)6:1<1::aid-aqc177>3.0.co;2-#
About the author: Ella Rose Steven is a student at the University of Auckland.