Whale shark, the world's largest fish, thrives on tiny crustaceans and worms

Monday, November 1, 2010; 3:29 PM

Big fish make a feast of small fry

How do the largest fish in the world survive on a diet of tiny crustaceans and worms? That's what 12 researchers from five institutions - the University of South Florida; the Georgia Aquarium; the Mote Marine Laboratory in Sarasota, Fla.; the University of California at Irvine; and Proyecto Domino, based in the Cancun, Mexico - set out to find when they studied whale sharks in the wild.

According to a new study published in the journal Zoology, the researchers documented how the sharks spend most of their time with their mouths open and angled upward at about 13 degrees to force water and food through filtering pads at the entrance to their throats.

The scientists estimate that a whale shark measuring 20 feet long takes in more than 162,000 gallons of water an hour and consumes 6,721 calories per day. By contrast, healthy humans eat between 1,600 and 3,000 calories per day depending on their age, sex and activity level, according to U.S. dietary guidelines.

In an interview, Robert Hueter, one of the paper's co-authors, said the findings demonstrate that even as humans try to develop complex filters that resist clogging, "these animals invented them tens of millions of years ago."

But this same mechanism could prove problematic for whale sharks passing through areas affected by the oil spill in the Gulf of Mexico, warned Hueter, who directs Mote's Center for Shark Research: "They're highly vulnerable because of this need to feed by filtering, or straining, the water."

- Juliet Eilperin

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