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article imageThe key to the Great White Shark’s power: a fat liver

By Tim Sandle     Jul 25, 2013 in Environment
The fuel source that allows the white shark to embark on incredibly long migrations through the world’s oceans has been identified as its liver, which is relatively large and fat compared with other creatures.
Scientists, using electronic tracking tags and observations, have identified that sharks fatten up for the demands of migration similar to the way that birds do. According to Wired, as sharks feed more in preparation they store up calories as oily lipids. This provides them with the energy to travel great distances. These lipids are stored in the liver; in fact, a maximum 90 percent of the volume of the liver is made up of high-energy lipids.
White sharks (Carcharodon carcharias) in the eastern Pacific swim from California to Hawaii during the spring and return in late summer. This is an 8,000-kilometer round trip and it takes about a month each way.
Most of the food comes from seals and other animals off the coasts of California and Mexico. However, as the sharks travel to Hawaii, food sources become scarcer.
Although the consumption of fats provides power, sharks lose some buoyancy. As the sharks were tracked during their trip to Hawaii they were seen to sink progressively faster during glides.
Commenting on the research, researcher Barbara Block, a professor of marine sciences and a senior fellow at the Stanford Woods Institute for the Environment, told Stanford News that: “We have a glimpse now of how white sharks come in from nutrient-poor areas offshore, feed where elephant seal populations are expanding – much like going to an Outback Steakhouse – and store the energy in their livers so they can move offshore again. It helps us understand how important their near-shore habitats are as fueling stations for their entire life history.”
The study was led by Gen Del Raye of the University of Hawaii in Manoa. A paper has been published in the journal Proceedings of the Royal Society B. The paper is titled “Travelling light: white sharks (Carcharodon carcharias) rely on body lipid stores to power ocean-basin scale migrations.”
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