World-first hybrid shark an indication of coping with climate change

by James Cook University on 5 Jan 2012 Marine biologists from James Cook University in Townsville Queensland 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.

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, according to Dr Jennifer Ovenden from the Queensland Department of Primary Industries and Fisheries.

'It was unprecedented because hybridisation between sharks in the wild has never been reported before in Australia or worldwide,' said Dr Ovenden.

The scientists were examining fish stocks when they found 57 of the hybrid sharks in a 2,000km 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.