Grey Nurse Shark - Carcharias taurus

Family: Odontaspididae

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The Grey Nurse Shark (Carcharias taurus) is one of the most endangered species in Australian waters. Two separate populations exist in Australian waters, a west coast population that is listed as 'vulnerable' and the east coast population that is listed as 'critically endangered'. The range of the east coast population is believed to extend from Wolf Rock in Queensland down to Montague Island in NSW. Research by scientists has found that there are less than 500 individuals remaining on the east coast of Australia. The species is also found in several other locations around the world. It is known as the Ragged Tooth Shark in Africa and the Sand Tiger Shark in the United States. The species is protected in the United States however in South Africa there is a recreational bag limit of 5 per person per day!

One of the major contributing factors to the species decline is its unusual reproductive biology. Grey nurses reach sexual maturity at 4-6 years for males and 6-8 years for females. They are an ovoviviparous species, meaning that they give birth to pups after they have hatched from eggs within the uterus. This is where the reproductive system gets interesting. Up to 15 embryos start developing in each of the two uteri and the two most advanced embryos in each uterus then eat all the other developing embryos and unfertilised eggs. This phenomenon is known as inter-uterine cannibalism. So they have basically eaten all their brothers and sisters before they are born!

The gestation period is also very long, lasting 9-12 months and the two pups are born at about 80cm to 100cm in length. Females only reproduce every 2nd year, therefore on average only 1 pup per female is produced per year.

The maximum size for the species is believed to be about 3.5 metres and it estimated they grow up to 25 years old in the wild. They are considered a harmless shark and are not a threat to humans unless they are provoked.

Research on the grey nurse sharks in Australia has found that they migrate north - south at certain times of the year. It is believed that their migration is in relation to changing water temperatures, as they are generally found in water temps from 18 - 24 degrees Celsius, and that they are also following prey species such as the jewfish and mullet.

As an endangered species, it is illegal for any person to target or keep grey nurse sharks in Australia. Penalties up to $220,000 and/or two years in jail apply to any person found harming the species in NSW and Qld. There are now management arrangements in place in NSW and QLD to protect critical habitat sites where grey nurse sharks aggregate to mate, pup and feed. Hopefully the protection of these sites will lead to a recovery in the east coast population of grey nurse sharks.

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