Side swim style saves shark energy

August 9, 2016 by Pepita Smyth

Hammerhead sharks swim on their sides up to 90 per cent of the time to save energy, a Murdoch University researcher has found.

Dr Adrian Gleiss from the Centre for Fish and Fisheries Research, collaborated on an international study which found the great hammerhead species spends up to 90 per cent of its time swimming at angles of between 50 and 70 degrees.

This is thanks to an exaggerated dorsal fin which generates lift and helps to reduce drag when the sharks are rolled on their sides.

Most sharks use their dorsal fins on their backs like a rudder on a boat, to facilitate quick turns. Their large pectoral fins on their sides are used like aircraft wings to keep them from sinking. It was thought this was how all sharks functioned until this study, which was led by Dr Nicholas Payne from the University of Roehampton, London.

Dr Gleiss and the research team used video cameras and tagging to measure roll angles in hammerhead sharks in Belize, Australia and The Bahamas.

"The co-lead author on our paper, Associate Professor Gil Iosilevskii, developed hydrodynamic modeling to show this swimming method reduces energy use by around 10 per cent, compared with traditional upright swimming," said Dr Gleiss.

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Landmark shark ban upheld at conservation meeting

By Matt McGrath, Environment correspondent, BBC News, Bangkok

Pro-shark fishing nations have narrowly failed to overturn a landmark protection deal struck at the Cites conservation conference in Bangkok.

Japan and China tried to block trade regulations on three critically endangered shark species by re-opening the debate in the final session.

But delegates refused the request by a wafer-thin majority and the shark ban was upheld.

The decision is being seen as a landmark win for animal conservation.

Campaigners say it is a truly historic day for the species, in which science triumphed over politics.

On Monday, the decision to increase protection for oceanic whitetips, porbeagle and hammerhead sharks had only scraped past the two-thirds majorities required by a handful of votes.

Campaigners had been extremely worried that China and Japan, the main opponents of the measures, would be able to muster the one-third support needed to re-open the debate and block the ban.

In a tense session here in the conference centre, they failed by just over 1%.

'Major step'

UK environment minister David Heath, who had just arrived in Bangkok, told BBC News that this was a great day for the Convention.

"I’m absolutely delighted. I think this is a major step forward today. What we saw was member states across the board say 'we are not going to be diverted from our path'," he said.

Continued:  http://www.bbc.co.uk/news/science-environment-21781949

Hammerhead Shark Double Whammy

ScienceDaily (Mar. 26, 2012) — Identity confusion between a new, yet unnamed shark species, originally discovered off the eastern United States by Nova Southeastern University Oceanographic Center (NSU-OC) researchers, and its look-alike cousin -- the endangered scalloped hammerhead shark -- may threaten the survival of both species.

According to an April 2012 article in the scientific journal Marine Biology, the new look-alike hammerhead species has now been discovered more than 4,300 miles away near the coast of southern Brazil. This confirms that the original finding was not a local oddity and the new species is much wider spread. The look-alike species may face the same fishery pressures as the real scalloped hammerhead, which is being fished unsustainably for its highly prized fins.

"It's a classic case of long-standing species misidentification that not only casts further uncertainty on the status of the real scalloped hammerhead but also raises concerns about the population status of this new species," says professor Mahmood Shivji, Ph.D., who oversaw the new research at the NSU-OC's Save Our Seas Shark Center USA and Guy Harvey Research Institute.

Read on:  http://www.sciencedaily.com/releases/2012/03/120326132801.htm

Sharks in Lake Macquarie killed for ‘thrills’

HAMMERHEAD sharks are being targeted by Lake Macquarie fishermen seeking food and thrills, and a washed-up shark is thought to have been hooked first.

A marine biologist said a hammerhead carcass found on Saturday at Myuna Bay, where another hammerhead beached and died last month, had probably been caught.

‘‘My guess would be that these sharks were killed and possibly dumped,’’ Department of Primary Industries shark biologist Vic Peddemors said.

‘‘I think it’s an incidental mortality rather than a natural mortality.’’

Some lake anglers are targeting hammerheads for their size and prestige.

Several videos of hammerheads in the lake have popped up on YouTube and one shows two men on a boat hooking a shark, reeling it in and letting it go.

Fishe rmans Warehouse, Marks Point, owner Jason Nunn said there was general consensus hammerhead numbers were increasing along with bull and whaler sharks.

‘‘Some [fishers] go out and hook them and let them go, some are taken home for food or trophies and some are released,’’ he said.

He said even a released shark could ingest a hook and die and wash up later.

He said it would be interesting to know if the hammerhead that beached in July had a hook in its stomach.

‘‘It could have been a fish that was released after the fight,’’ Mr Nunn said yesterday.

One YouTube clip shows a hammerhead lurking in what the poster claims is the nearby Eraring Power Station’s outlet.

The station sucks in water to cool itself through inlets designed to divert fish and return them to Myuna Bay. Surrounding water can reach 35degrees.

Dr Peddemors said water that warm would not harm a shark and there was probably no link between the station and the dead hammerheads.

BY TIM CONNELL, PORT STEPHENS REPORTER

http://www.theherald.com.au/news/local/news/general/sharks-in-lake-macquarie-killed-for-thrills/2259199.aspx