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Grey Nurse Sharks: Wired for sound and survival
The movement patterns of the critically endangered grey nurse shark are about to be revealed in a new study set to improve the species chances of survival.
Scientists from CSIRO and NSW Fisheries are tracking the movement of grey nurse sharks using special electronic tags that allow them to be continuously monitored.
Grey nurse sharks became the worlds first protected shark in 1984, following indiscriminate killing of the species in the 1960s. However the east coast population has failed to recover and is now listed as critically endangered, under the Commonwealths Environment Protection and Biodiversity Conservation (EPBC) Act.
"Grey nurse sharks aggregate at sites along the NSW and southern Queensland coasts. Tracking their movements will give us a much better understanding of how long sharks stay at these sites and how wide an area around these sites they commonly use," say team leaders Barry Bruce and Dr John Stevens from CSIRO Marine Research in Hobart.
The tags, which are applied underwater by divers using a tagging pole, continuously transmit the swimming depth of the sharks using sound waves and allow scientists to follow them from a boat.
"The effectiveness of measures to protect grey nurse sharks will depend on the amount of time the sharks spend at these sites and how far they move away from the sites during their daily activity patterns," says Mr Bruce.
The next phase of the study involves placing automated listening stations on the bottom that continuously monitor the presence of grey nurse sharks which are fitted with a second type of tag.
"These tags will tell us when a shark is at one of the sites, how long it stays and when it leaves" explained Mr Bruce. "We have been using the same technology to monitor movements of white sharks in South Australian waters," he said.
The research complements a longer term tagging study recently initiated by NSW Fisheries, which is marking grey nurse sharks with specially numbered tags that divers can see and record underwater.
"This combination of tagging technologies offers our best hope of revealing how grey nurse sharks use the areas around aggregation sites and how they move between them" said NSW Fisheries Research Scientist, Dr Nick Otway. "This will allow us to more accurately assess their numbers".
The grey nurse, once undeservedly labelled as a man-eater due to its fierce appearance, is harmless and feeds on fish, smaller sharks and rays.
The study is supported by the Commonwealth Governments Natural Heritage Trust and involves the NSW Marine Parks Authority (Coffs Harbour), Underwater World (Mooloolabah) and local dive groups.