Great white sharks have neighbourhoods


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The Census of Marine Life has once again come up with a surprising new fact; that Great white sharks have neighbourhoods and that they hang out in shark cafes.

You won t be finding them on your local high street, but the study has found that sharks are actually homebodies that like a routine.

The study which is part of the TOPP (Tagging of Pacific Predators) programme used satellite tagging, passive acoustic monitoring and genetic tags over a period of eight years to track the Great whites (Carcharodon carcharias). It found that the sharks were so faithful to their own area that individual populations are becoming genetically distinct.

So far there are three distinct ~clades off the coast of South Africa, in the waters between Australia and New Zealand and the newly discovered one in the northeastern Pacific. This population is thought to have been founded by a relatively small number of sharks within approximately the last 200,000 years.

Salvador Jorgenson from Stanford's Hopkins Marine Station and the lead author of this paper said:

"White sharks are a large, highly mobile species. They can go just about anywhere they want in the ocean, so it's really surprising that their migratory behaviours lead to the formation of isolated populations."

The sharks were found to make huge solitary migrations along extremely predictable routes. Between August and December, the white sharks feed in the waters off the coast of central and northern California in an area known as the "red triangle".

Further studies showed that sharks seem to have favourite spots to feed which they can remain in for up to 107 days.

Starting in January, they head around 4,000 km west towards Hawaii, where they are found in largest numbers between April and July. Some - especially males " stop off at a point approximately halfway between the Baja Peninsula and the Hawaiian Islands in area which has been dubbed the "White Shark Cafe". Scientists think that females probably pop in on occasion for a bit of "shark love"!

Barbara Block, professor of marine sciences at Stanford and a co-author of the paper, said, "Catastrophic loss of large oceanic predators is occurring across many ecosystems. The white sharks' predictable movement patterns in the northeastern Pacific provide us with a super opportunity to establish the census numbers and monitor these unique populations.

"This can help us ensure their protection for future generations."

With over a third of the world's sharks threatened by extinction through shark finning and bycatch, this study shows how vulnerable a restricted population that does not appear to interbreed with other populations could become, if too many individuals were taken.