Basking sharks trek across Atlantic

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Basking sharks trek across Atlantic

October 13, 2010 - 01:10
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When basking sharks mysteriously disappear from the cool waters of the Atlantic and Pacific Oceans where do they go? For decades, the whereabouts of world's second largest fish have baffled experts.

Basking shark off Cornwall, UK

Giant basking sharks like to take tropical vacations too.

Previously thought to inhabit only temperate waters, a new study, just published in Current Biology, shows that the giant sharks make long, make vast migrations to deep, warm-water hideouts. Before the annual winter disappearance, scientists tagged 25 basking sharks off New England with floating, timed-release satellite transmitters, which showed that, like humans, the giant basking sharks like to take tropical vacations too.

Unexpected Hideout Found
Swimming at depths of between 200 and 1,000 meters, some of the fish moved to Florida. But others kept on going south—thousands of miles, into the Carribean Sea and one shark even crossed the Equator to the mouth of the Amazon River off Brazil, where the fish stayed for a month.

Why So Far?
What is driving these giant sharks to migrate such vast distances remains unclear mystery but they probably seek warmer waters to feed when plankton is more abundant there. But that doesn't explain why they go all the way to Brazil when food is abundant around Florida.

No young ever seen
One theory is that they're heading to undiscovered nursery grounds. Scientists have never seen a young basking shark and they still have no idea where they give birth.

The International Union for Conservation of Nature lists basking sharks as being vulnerable to extinction. The new discovery could help address threats facing the sharks.

"Tracing basking sharks on these journeys begins to tell us much more about the population structure. What were thought to be regional stocks may in fact belong to a single, oceanwide population."
—Mauvis Gore, biologist from Marine Conservation International

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