Grey Nurse Shark
By Jack, Jake M and Michael
| Grey nurse sharks are described as: stout bodied, with conical
snouts, long, slender teeth, small eyes, two large dorsal fins, and a
tail with a upper lobe longer than the
lower one, and metallic brown blotches and paler undersides. Very few
types of sharks are protected, but in New South Wales the Grey Nurse
Shark was protected. In 1985 they became the first sharks to be protected in
Australia. The Grey Nurse Shark has three names Sand Tiger Shark, the
Ragged-Tooth Shark and the Grey Nurse Shark. The Sand Tiger Shark is the
American name for the Grey Nurse and the South African name for the Grey
Nurse is the Ragged Tooth Shark. Did you know that you can tell a shark's age by how many rings on its vertebrae (backbone)? Most sharks grow one ring each year. |
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The Grey Nurse shark have been protected on the north-west shelf of
Western
Australia. In the 1970`s fines up to $10,000 can be imposed for
killing a Grey Nurse shark. When the film JAWS was being filmed Grey
Nurse Sharks were aggressively hunted in the mistaken belief that they
were dangerous, but in fact they are harmless. Like most sharks, Grey
Nurse Sharks are slow to mature and have relatively few young. In the
case of the Grey Nurse Shark, only two pups are born at a time. There is
a large group of Grey Nurse Sharks usually
found between April and November North of Sydney ( Seal Rocks).
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| When pups are born they are about 115-150 cm long and mature Grey
Nurse Sharks grow up to 5.5 meters. The Grey Nurse Shark feeds on small
sharks, as well as rays, bony fish, squid, crabs and lobsters, and
sometimes hunts in groups. Grey Nurses swallow air at the surface and
hold it in their stomachs to give themselves just enough buoyancy to
hang almost motionless above the sea bottom in their feeding site.
Numbers of Grey Nurse have declined dramatically over the last
decade, and species may become extinct in the near future. 98% of Grey
Nurse is now only found in 8 sites. Numbers have declined from all
other sites as well.
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Over several months, the Grey Nurse females produce over millions of tiny eggs, packaged in capsules. Inside each egg, a strong embryonic shark feeds initially on its own egg yolk, but once it develops teeth (which happens when it is around ten cm long), it gobbles up the other eggs in its capsule. It then breaks the capsule and hunts down and eats its siblings, so that only one baby shark in each uterus survives. This ensures that only healthy, well developed sharks that are capable of looking after themselves after birth are born. If you think the Grey Nurse Shark can badly injure you, you are wrong. In fact, they are harmless unless provoked. During the day Grey Nurses of different ages and sizes gather in groups, but they probably hunt at night alone. The Grey Nurse Shark is usually sighted between April and November. The biggest Grey Nurses are found at the Atlantic. |
| Many sharks lead extremely active lives, so they need an efficient supply of oxygen to their muscles and organs. Sharks breathe out oxygen from the water by taking it in through their mouth, allowing it to flow over their gills and then expelling it through their slits. Sluggish, bottom-living species such as Catsharks and Wobbegongs use special muscles to pump water over their gills even while at rest. But fast, highly active species such as Mackerel sharks use their forward motion to force water through their gills; a process known as ram-jet ventilation. These sharks must keep swimming in order to breathe. Between these extremes are species like the Grey Nurse which pumps water over its gills at rest, but switches to ram-jet ventilation when swimming to save energy. |
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Fact File Scientific Name: Carchais taurus. |
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Click here to go to the Grey Nurse Activity Page
