Natures wonders: Tiger shark migration (Introduction)

by David Turell @, Wednesday, June 10, 2015, 15:34 (1648 days ago) @ David Turell
edited by David Turell, Wednesday, June 10, 2015, 15:52

Atlantic sharks travel north in summer thousands of miles and return to the same Caribbean islands in winter:

http://www.sciencedaily.com/releases/2015/06/150609213349.htm

"The researchers were able to show that adult male tiger sharks in the Atlantic repeatedly spend their winters in Caribbean island locales including the Bahamas, Turks and Caicos Islands, and Anguilla. Then, during summers, they travel far into the North Atlantic, often more than 3,500 kilometers and as far north as Connecticut, though well offshore in nearly the middle of the ocean.

"'These repeated journeys were very unexpected,' said Lea, who also works out of the Marine Biological Association of the United Kingdom, 'The tiger shark has traditionally been considered a coastal species, and it is rare among sharks to so easily and habitually switch between the two vastly different environments.'

"Remarkably, the sharks followed the same pattern each year and returned to almost the same small area in the Caribbean each time.

"'Even though they've got a whole range of islands to choose from, it seems like each animal has its favorite winter spot,' said Shivji.

"For the tiger sharks, the migrations are something like a 'highway road trip,' on their way to definite destinations. Bermuda is a handy spot for tiger shark tagging because it is the equivalent of a popular highway exit -- lots of animals stop off there for a break while heading north or south. But for the most part the animals travelled directly between their migration destinations, meandering around only after arriving.

"What makes the tiger sharks so committed to particular areas is still an open question. At the south end, the story may be fairly simple. Female tiger sharks are common in the Caribbean in the winter, so the Caribbean may just be the best place for male tiger sharks to find dates, although this is just an educated guess."


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