Marine life adapts to warm seas (Australia)

May 13, 2013 (Michelle Wheeler). Whale sharks off Perth, irukandji jellyfish at Ningaloo Reef and humpback whales giving birth 2000km from their usual calving grounds have left biologists baffled as they investigate whether an ocean heatwave is to blame for marine life turning up in unexpected places.

At Ningaloo Reef, scientists are looking into a spate of stings last month from highly venomous irukandji jellyfish, usually found near Broome.

Department of Environment and Conservation Ningaloo Marine Park co-ordinator Peter Barnes said one theory was that it was related to unusually high water temperatures in the past three years.

“Usually over a summer we might get one sting, maybe two, sometimes none, but we had 13 reported stings over about a month, which was an extremely unusual occurrence,” he said.

Closer to Perth, the Fisheries Department has recorded tropical fish at Rottnest Island never before seen so far south or in greater numbers.

University of WA scientists also published a study last year in the prestigious journal Nature Climate Change suggesting the proportion of tropical fish at Jurien Bay had risen from 5-10 per cent to up to 20 per cent.

Fisheries principal research scientist Gary Jackson said reports of unusual species appearing off Perth and further south began two years ago.

The ocean heatwave, first reported in the summer of 2010-11, has been cited as the reason for recreational fishers catching tropical species off Perth and blamed for coral bleaching at Ningaloo.

Fisheries has also claimed that cool water forced towards the WA coast by warmer tropical water flowing south may have been responsible for an increase in shark activity off the metropolitan coast.

Southern WA is not immune either, with Weather Bureau data showing water temperatures on the south coast this year are the highest on record.

DEC whale expert Doug Coughran, who has been keeping records for 30 years, said there had been reports of humpback whales giving birth off the south coast, up to 2000km from their usual calving grounds.

In March, a Japanese devil ray, usually found in tropical waters in the Pacific and Atlantic oceans, washed up on Cheynes beach, east of Albany. It was photographed by Fisheries and reported to Redmap, a website that logs unusual marine sightings.

Redmap chairwoman Gretta Pecl said the site was set up in response to research suggesting between 18 and 80 per cent of animals worldwide were shifting their range.

“There’s a lot of things all around the world that are shifting and the vast majority of these shifts are going towards the poles,” she said.

Ecocean director Brad Norman said whale sharks were cryptic animals and it was possible they had always gone south or the sightings were simply a case of “one lost shark”.

‘We had 13 reported stings over about a month, which was an extremely unusual occurrence.'” Ningaloo Marine Park co-ordinator Peter Barnes.

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