A new study has looked at a shark's changing buoyancy over time to track the depletion of its fat reserves during its long migration.
Before a shark makes a long trip, it has a snack – a seal snack.
Scientists have found that the great white shark makes its 2,500-mile-long journey through the western Pacific only after feasting on seal fat and packing the oil in its gargantuan liver. That oil is the shark's sole sustenance during the food-scarce haul from California to Hawaii.
“Scientists have known that the size of sharks' livers fluctuates widely, and that this variation reflects food availability,” says Salvador Jorgensen, a post-doctoral research associate at Stanford University and Monterey Bay Aquarium and a co-author on the study, published in Proceedings of the Royal Society B.
“We have been able to finally demonstrate that a well-fed white shark in our aquarium becomes more buoyant with increasing energy stores, and in the wild, the sharks are using those stores to fuel vast migrations,” he said.