Scientists solve mystery of missing basking sharks

Head south, young basking shark. Way, way south. And way deep, while you're at it.

That's the unexpected advice the world's second largest fish seem to be taking -- at least in the Western Atlantic.  To some marine scientists, the newly discovered itineraries these gentle giants follow could have significant conservation implications.

The International Union for the Conservation of Nature and Natural Resources lists the fish as "vulnerable" to extinction. The new wrinkles in their migration patterns appear in a recent study in the journal Current Biology. The results suggest that efforts to conserve these creatures may not work if those efforts are limited to one or two ocean basins, notes Gregory Skomal, the lead scientist behind the shark-tracking project.

Other research, which focuses on basking-shark genetics, already has hinted that this approach might be needed, he adds. Now, the latest shark-tracking information gives that earlier work additional gravitas.

Until now, conventional wisdom held that tropical waters presented a barrier to basking sharks as they migrated north and south each year.  As marine biologist Elliott Norse puts it during a phone chat about the results, you looked to the temperate oceans for basking sharks and to tropical oceans for whale sharks, the largest living fish.

But a team led by Dr. Skomal, a marine biologist with the Massachusetts Division of Marine Fisheries  now has tracked basking sharks from the start of their journey in waters off southeastern Canada and the northeastern US all the way to the coasts of Brazil, well into the southern hemisphere. Until now, the farthest south the creatures had been tracked was to waters off the US Southeast.

So much for a barrier for basking sharks.

So big a fish, so little known

"Here it is May 2009, and we are still discovering really surprising new things about one of the biggest animals on Earth," enthuses Dr. Norse, who heads the Marine Conservation Biology Institute in Bellevue, Wash. "This is a beautiful example of things we had assumed we understood based on what what we could see, and we find out that they are not true."

Basking sharks get their name from their tendency to swim close to the surface along continental coastlines. That's where their food, plankton, hangs out.

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