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New research shows reasons to protect the Great White Shark
If efforts to protect the great white shark are neglected, the species could become as rare as the giant panda. New research published in the journal, Nature, shows that male sharks tend to undertake transocean excursions, with females staying in home waters. This behaviour is closer to warm blooded mammals, such as ourselves, than to fish, and also may lead to great white sharks being especially vulnerable to sharp decreases in population.
Scientists from the universities of Aberdeen (Les Noble, Cathy Jones and Amanda Pardini) and Boulder Colorado (Andy Martin and Brian Kreiser) together with an international consortium of shark samplers (Michael Scholl, Hamish Malcolm, Barry Bruce, John Stevens, Geremy Cliff, Malcolm Francis and Clinton Duffy) have, for the first time, shown that differences in the dispersal behaviour of male and female great white sharks are more akin to warm blooded mammals than to cold blooded fish. Their findings have been published in the latest issue of the journal, Nature.
The researchers used advanced molecular genetic techniques on the largest collection of white shark tissue samples ever assembled to gain ecological information about this rare, large and ferocious species which could not be collected by traditional tagging and observational approaches. They were able to show that there are differences in the dispersal of sexes, with roving males undertaking occasional transoceanic excursions, whereas females preferred to stay in home waters.
This means that local populations of white sharks are vulnerable to over fishing, as females killed in one population will not replaced by migration of females from neighboring populations. Other shared life history features of this species, such as low fecundity, long life span, and late age at maturity also add to its vulnerability and, together with differences in dispersal of the sexes, suggest that the population biology of white sharks may be more similar to that of marine mammals than to other fish.
The great white shark is listed as 'vulnerable' on the IUCN list of threatened animals, so these findings have immediate relevance for conservation strategies. The global dispersion of males may indicate that the future sustainability of wide spread populations is linked, underscoring the need for international regulations governing exploitation.
This work sheds light on long-standing questions on the movements of the great white, such as do sharks migrate across oceans?, do populations in different parts of the world interact?, do the sexes have different behaviours?, does such a physiologically advanced shark behave more like a mammal? - none of which could be addressed by traditional tagging and observational data.
Although likely to receive less sympathy this top predator of the oceans could be potentially as vulnerable as the giant panda if its conservation is neglected - but with less recourse to captive breeding programmes these results suggest great white shark conservation needs active management strategies to be implemented without delay.
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