Great white sharks eat far more than believed 
 
 (AFP) – Mar 20, 2013 
 
 SYDNEY — Great white sharks, the world's largest predatory fish, eat three to four times more food than previously thought, an Australian study shows. 
 
 US research from the 1980s estimated a 30 kilogram (66 lbs) meal of mammal blubber could sustain a one-tonne shark for more than six weeks. 
 
 That perpetuated assumptions that large sharks could survive long periods without eating. 
 
 However, a University of Tasmania-led study published this week in Scientific Reports on the nature.com website found that 30 kilos was only enough for 12-15 days. 
 
 Researchers tagged a dozen great white sharks at Neptune Islands off South Australia and calculated their metabolic rate derived from swimming speeds. 
 
 They worked out how much energy the sharks burned and how much food they required. 
 
 Senior research scientist Jayson Semmens, lead author on the study, said the amount of energy required by great white sharks was equivalent to eating a seal pup every three days. 
 
 "They (US researchers) picked a shark that probably wasn't working very hard at the time when they did it," Semmens told ABC television. 
 
 "At the time it was a really novel study. They did some metabolic work similar to us but on one shark. 
 
 "The white sharks at a seal colony where we worked, they're working pretty hard, ... they're coming up to some pretty high speeds to catch the seals. 
 
 "Their metabolic rate or the engine that runs them is much faster than what we had assumed. 
 
 "These animals are probably going to be feeding you know every few days, rather than multiple weeks." 
 
 The research also sought to improve understanding of how sharks fit into the ocean ecosystem. 
 
 "We don't have a good handle on the population sizes of white sharks. We know that sharks in general are under pressure around the world from overfishing," he said. 
 
 "They're quite vulnerable because of their life history, they're long-lived, they reproduce late in their life and they produce a small number of offspring." 
 
 Semmens said the knock-on effects of removing white sharks from the ocean were thus far more important than realised. 
 
 "They're keeping under control a lot more animals than we thought," he said. 
 
 The apex marine predators, which grow up to five metres (yards) long and weigh an average 1,300 kilos, are protected and found around the globe. 
 
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 Great whites bite more often than thought 
 
 Updated 
 
 In an alarming finding for swimmers, new research has suggested one of the most feared marine creatures needs to feed much more often than previously believed. 
 
 A team from the University of Tasmania has studied 12 great white sharks near Neptune Island off the South Australian coast. 
 
 Waters off the island attract sharks that feed on seal pups from the nearby colony. 
 
 The research aimed to shed light on the eating habits of the creatures which scientists say are poorly understood. 
 
 Marine biologist Jayson Semmens says 1980s American research suggested the sharks could survive for about six weeks on a single 30-kilogram meal. 
 
 Dr Semmens says the new study shows sharks can only go up to 15 days between meals of that size, debunking the older research. 
 
 "They picked a shark that probably wasn't working very hard at the time when they did it," he said. 
 
 "At the time it was a really novel study. They did some metabolic work similar to us but on one shark and they suggested that a white shark only needed to feed every six weeks. 
 
 "That idea had really perpetuated itself through the community and particularly scientists. 
 
 "The white sharks at a seal colony where we worked, they're working pretty hard, they're patrolling the colony, they're coming up to some pretty high speeds to catch the seals. 
 
 "We found that if you use the same amount as what they suggested, a 30-kilogram meal, then these animals will have to feed every 10 or so days so a lot more regularly. 
 
 "Their metabolic rate or the engine that runs them is much faster than what we had assumed. 
 
 "These animals are probably going to be feeding you know every few days, rather than multiple weeks." 
 
 Dr Semmens says the research also aimed to improve understanding of how sharks interact with the ocean ecosystem. 
 
 "We don't have a good handle on the population sizes of white sharks. We know that sharks in general are under pressure around the world from overfishing," he said. 
 
 "They're quite vulnerable because of their life history, they're long-lived, they reproduce late in their life and they produce a small number of offspring." 
 
 Topics: marine-biology, human-interest, animal-science, sa, adelaide-5000, port-lincoln-5606, port-pirie-5540, tas, university-of-tasmania-7005 
 
 First posted
– Great white sharks are a lot hungrier than scientists realized, a new study suggests. The old line of thinking, based on research done in the 1980s, is that a great white could snack on, say, a 60-pound seal pup and go six weeks without another meal. As it turns out, it's more like two weeks, max, say researchers at the University of Tasmania, reports AFP. In fact, the sharks are likely to be feeding every few days, not every few weeks. The findings are based on a meticulous study of a dozen sharks that factored in their metabolic rate and swim speeds. So why was the old study so far off? The best guess is that "they picked a shark that probably wasn't working very hard at the time when they did it," one of the new researchers tells Australia's ABC News.