Grey Nurse Shark
THE GREYNURSE SHARK
Sharks! Swimming around in the ocean surrounded by sharks is probably not for everyone. But a deeper understanding of the sharks and the important role they play in our marine ecosystem will hopefully inspire more people to help save the lives of sharks. So, let’s take a deeper look into the ‘labradors of the sharks’ our Greynurse sharks.
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These sharks are critically endangered despite them being protected not only in the waters of New South Wales but also globally. In Australia, Greynurse sharks are restricted to two populations, one on the east coast and one on the west coast. It is believed that these shark groups do not interact and that the East Coast population is genetically distinct! The Greynurse Shark (east coast population) population is estimated to be between 1146 and 1662 individuals only.
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Scientific name: Carcharias taurus Alternative names: Spotted Ragged-Tooth
Similar species: The family Odontaspidae contains two genera: Charcharias and Odontaspis. Both species occur in Australian waters, the Greynurse Shark and Sandtiger Shark (Odontaspis ferox) Size: Average size 1-2.6 metres. The largest Greynurse Shark was measured at 3.18 metres.
Did you know?
• Shark babies are called pups.
• The fact that they show their teeth is not an act of aggression as with other shark species.
• Male Greynurse Sharks reach sexual maturity at 7-11 years of age, and females at 10-14 years of age.
• Mating occurs in the late autumn months and pups are born just around winter.
• They have the lowest reproductive rate of any shark making it more susceptible to external pressures.
• The teeth of the Greynurse Shark are constantly being replaced.
How can you spot it?
The Greynurse Shark has an extra dorsal fin that makes it easy to distinguish from other sharks. The two dorsal fins are almost equal in size. Their colour is usually a bronze colour with a paler underside. Younger GNS have brown spots on their body and sometimes these can disappear over time. Generally, these sharks are lonesome travellers and will only appear in groups during mating time.
What do they eat?
They usually feed on fish, crustaceans, octopuses and rays. They pierce the animals with their sharp teeth.
Where do they live?
These slow-moving sharks live in shallow coastal waters, usually in the vicinity of dropoffs, caves and ledges.
In NSW several sites have been identified as greynurse critical habitats. These zones are especially protected areas to help save this critically endangered species.
What is their lifecycle?
Greynurse Sharks are ovoviviparous which means they produce eggs that hatch internally and then the pups are born without a placental connection.
Eggs hatch in the two uteruses of a female shark after being fertilized. The eggs hatch inside the uterus and using oophagy (egg-eating) and intra-uterine cannibalism only two shark pups are born from each litter. A female will only reproduce every two years.
What can you do to help protect this beautiful shark?
Photographers can participate in citizen science projects by sending in their images of Greynurse Sharks to “Spot a Shark” or “Greynurse Shark Census”. Based on the images sharks can be identified and counted. The most recent population estimate for GNS undertaken by the CSIRO and NSW DPI in 2018 found that there were approximately 2000 adult Greynurse sharks along our Australian east coast.
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When diving or snorkelling:
• DO NOT block entrances to caves and gutters when the sharks are there
• NO feeding
• NO touching
• NO chasing or harassing the sharks in any form
• NO electronic shark-repelling devices
• NO underwater scooters
• NO sunset or night dives in areas that are critical for the survival of the sharks
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Greynurse Sharks are threatened by recreational fishing as they can take the baited hooks. These hooks can get infected and cause death to the animal when they get caught in the jaws or puncture their internal organs. So, if you spot someone fishing in a protected zone, please make them aware and/or report this person to the relevant authorities.
How can you help protect the Greynurse Sharks but you don’t dive or snorkel?
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Every one of us can help support the population growth of this endangered species! The natural habitats of the GNS are being destroyed by commercial businesses but also due to pollution. Pollution is a huge topic and it might make us feel where to start or stop with making changes.
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But, there are simple ways on how you can be more sustainable at home and even in this way have an impact on the wellbeing of the sharks. Every little step counts. And the more people make little steps towards being more sustainable then it becomes huge in no time.
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Check out some of Hadassa's FIVE SIMPLE STEPS TO BECOME MORE SUSTAINABLE AT HOME.
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Let’s make a difference for our beautiful Spotted Ragged-Tooth or Greynurse Shark!
Webpage written by Hadassa
References
1. Australian Museum website
2. www.mesa.edu.au/seaweek/2005
3. Greynurse Shark Census
4. Cardno Ecology Lab 2010 - East Coast GNS population