World first "hybrid shark" found off Australian coast in large numbers

Avalon Beach near Sydney, Australia, is closed to the public after a shark attack on a surfer on March 1, 2009.</p>

Avalon Beach near Sydney, Australia, is closed to the public after a shark attack on a surfer on March 1, 2009.

Aussie scientists have discovered what they say is the world's first hybrid shark.

In an "unprecedented find," researchers say 57 of the new "tropical" sharks — a cross between the "genetically distinct" common blacktip and the Australian blacktip — were discovered along 1,242-mile coastline between the states of New South Wales and Queensland.

The two species generally inhabit different temperature waters — the Australian black tip generally north of Brisbane, and the bigger common black tip in cooler southeastern coastal waters.

Australian blacktips reach 5.2 feet; common blacktips in that part of the world reach 6.6 feet.

University of Queensland research scientist Jess Morgan told The Australian newspaper that hybridization was common in plants and some species of fish because of their external fertilisation. "They just release their eggs and sperm into the water column," she said.

"[But] sharks physically mate, which is usually a good way to make sure you don't hybridize with the wrong species."

"This is evolution in action," Morgan later told Agence France-Presse, adding that the hybridizing was a method of "range expansion" for the shark. 

The scientists believe the animals may be adapting to climate change.

However, Morgan said that while the combined DNA "could certainly give the sharks more genes to cope with change in the environment," she didn't think interbreeding was "a result of climate change per se."

Now, to the question playing on everyone's mind: Does adaptation make them more of a threat to humans?

The Australian again:

Dr Morgan said that while neither black tip species was considered a man-eater, they looked the part and hybridization could make them stronger.

One hope for the human oceangoer — particularly those vacationing in one of Australia's many coastal resorts:

The university and government researchers say it is too early to tell why the hybrid sharks are themselves capable of reproducing -- unlike mules, for example -- or whether they'll supplant their parent species, but they say the discovery suggests other similar shark and ray species could also be interbreeding and improving their ability to adapt to climate change.

Colin Simpfendorfer, Morgan's research partner had more bad news for the faint-hearted, quoted by AFP as saying that the phenomenon "may be happening in more species than these two."