Found basking in the waters of the Caribbean

How do you lose the world's second-largest fish? It had been happening for decades to researchers studying the basking shark, a plankton-eating species that can grow to be 35 feet long. Only the whale shark is bigger than this.

Sudden disappearance

Basking sharks were easy to spot in summer and autumn. Many cruised near the surface off New England, filtering water through an impossibly wide mouth.

But then, in winter, the sharks vanished from these waters and scientists couldn't find them anywhere else.
One guess was that they sank to the bottom and hibernated, waiting out a food shortage.

But nobody knew for sure: The basking shark became a reminder of the unsolved mysteries of the ocean.

Recently, however, a group of researchers from Massachusetts and Maine said they had found the answer. Like many New Englanders, the basking sharks spend their winters in the Caribbean.

The scientists, whose study was published in the journal Current Biology, had tagged 25 sharks off Cape Cod with tracking devices, designed to release from the animals' skin after days or weeks and transmit data about where it had been.

Tagged teams

Soon, the tags began popping up in places that nobody expected a basking shark to be: near the Bahamas, off Puerto Rico and even the mouth of the Amazon River in Brazil.
The sharks had remained undetected because they stayed so deep — between 650 and 3,300 feet — that they were not caught in fishing gear.

There is more plankton in warmer waters, scientists said. But it would be abundant enough off Florida, so there would be no reason to visit Brazil.

Gregory B. Skomal of the Massachusetts Division of Marine Fisheries said there could be another reason drawing the sharks south. Female sharks could be giving birth and raising the young in tropical waters.

“We've never seen pregnant females and we've never seen a newborn basking shark,'' he said.

That could be because they haven't been looking in the right place. Skomal said the data could be used to add protection for the sharks in the newly discovered habitat.