The National, Friday 06th January 2012
THE world’s first hybrid shark which has been found in waters off Australia also inhabit waters in southern Papua New Guinea, scientists in Australia announced this week.
It is a discovery which they say could have implications for the whole world.
The predators are a cross between the common blacktip shark and the Australian blacktip shark which are also found in PNG.
Scientists said on Wednesday that interbreeding between the two species is a sign the animals are adapting to warmer waters. They had also warned it could make the sharks stronger.
One of the scientists who made the discovery Dr Colin Simpfendorfer, of James Cook University’s Fishing Research Centre told The National yesterday: “These species definitely occur in southern Papua New Guinea.
“As such there is certainly a good chance that hybrids are also occurring in PNG waters.”
He says the farthest north that they have found them was on Cape York which was also as far north as they looked.
“Since both species do occur in PNG it is possible that they are hybridising there – but that would need to be confirmed by genetic testing,” he added.
“We would love to get samples from PNG to investigate, but have no plans at this point to sample up there.”
Simpfendorfer added that these sharks look exactly like one or other of their parents and posed no threat to humans at all.
When it is said that they are possibly “stronger” it means that they may be better able to survive, not that they are physically stronger, he explained by email.
Hybridisation happens among many species in the animal kingdom, including birds and some fish, but until now has been unknown among sharks.
According to the announcement on Wednesday, leading researchers in marine biology, including Simpfendorfer, discovered 57 animals along a 200km stretch of ocean from Queensland to New South Wales, and believe it is a sign the animals are adapting to climate change.
Dr Jess Morgan, of the University of Queensland, said it was unusual for sharks to breed this way: “Sharks physically mate, which is usually a good way to make sure you don’t hybridise with the wrong species.”
Simpfendorfer agreed: “The results of this research show that we still have a lot to learn about these important ocean predators.”
He said that if the hybrid proved to be stronger than the two pure breeds, it might eventually replace them. “We don’t know whether that’s the case here, but certainly we know that they are viable, they reproduce and that there are multiple generations of hybrids.
“Certainly it appears that they are fairly fit individuals.”
Dr Jennifer Ovenden of the Queensland department of primary industries said: “Hybridisation could enable the sharks to adapt to environmental change, as the smaller Australian black tip currently favours tropical waters in the north (which includes PNG) while the larger common black tip is more abundant in sub-tropical waters along the south-eastern Australian coastline.”
She said it was an “unprecedented” find. “Wild hybrids are usually hard to find, so detecting hybrids and their offspring is extraordinary,” she told The Australian newspaper.
“To find 57 hybrids along 2,000km of coastline is unprecedented.”
The scientists were examining fish stocks when they found 57 of the hybrid sharks. “Species with the smaller body can hybridise with the species with the larger body, allowing that tropical species to move further south,” Ovenden said.
“We are thinking that it will provide the sharks with a mechanism to adapt to future environmental change.”
Simpfendorfer concludes that the discovery would 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.
James Cook University fisheries researcher David Welch says it was 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, but not PNG as yet.