January 3, 2012 § Leave a comment
Updated January 03, 2012 20:53:48
More than 50 of the hybrid sharks were found in a 2,000-kilometre stretch of coast.
Marine biologists say they have discovered the world’s first hybrid sharks off Australia’s east coast, a potential sign the predators are adapting to cope with climate change.
They say the mating of the Australian black-tip shark with its global counterpart, the common black-tip, is an unprecedented discovery with implications for the entire shark world.
“It was unprecedented because hybridisation between sharks in the wild has never been reported before in Australia or worldwide,” said Dr Jennifer Ovenden from the Queensland Department of Primary Industries and Fisheries.
The scientists were examining fish stocks when they found 57 of the hybrid sharks in a 2,000-kilometre stretch of coast. They are a cross between two related but genetically different species.
The larger common black-tip shark swims in the colder waters of southern Queensland and northern New South Wales, while the smaller Australian black-tip likes warmer seas.
Dr Ovenden says there is a good reason why these sharks interbreed.
“Species with the smaller body can hybridise with the species with the larger body, allowing that tropical species to move further south,” she said.
“We are thinking that it will provide the sharks with a mechanism to adapt to future environmental change.”
Hybridisation happens among many species in the animal kingdom, including birds and some fish, but until now has been unknown among sharks.
Dr Colin Simpfendorfer, director of the Fishing and Fisheries Research Centre at James Cook University, says the discovery will help expand scientific understanding of sharks.
“It’s obviously a very interesting observation because we’ve never seen hybrid sharks before, and so it’s been hypothesised that it’s possible but we’ve never had any proof that it happens,” he said.
JCU fisheries researcher David Welch says it is a remarkable discovery.
“They actually choose a mate. It’s not like a fish where they actually put eggs and sperm into the water and they can potentially mix,” he said.
“Animal species tend to know their own kind, but in this case there seems to be a high prevalence of them interbreeding.”
The scientists are planning to look for hybridisation in other waters, including the western and northern Australian coasts
Sharks play an important role in the health of the marine environment. Sharks are known for being one of the few animals that never evolved over millions of years as they were perfectly suited to the ocean environment and did not need to adapt. However the new hybrid sharks show that global changes have caused the sharks to begin to process of evolution in order to survive.