Great White Sharks are NOT endangered: Study shows the number of predators is ten times higher than previously thought
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In 2011 an alarming study by Standford University suggested Great White Sharks were becoming an endangered species.
But new look at research on them in the Eastern North Pacific Ocean indicates the population is now growing thanks to conservation efforts, according to an international research team.
And the lead author of the study says the 2011 study underestimated the number of Great White Sharks in the oceans - and it should not be regarded as an endangered species.
A new look at research on Great White Sharks in the Eastern North Pacific Ocean indicates the population is likely growing rather than endangered. A Great White Shark is pictured in the Eastern North Pacific in this undated handout photograph courtesy of Kevin Weng, University of Hawaii
George Burgess, director of the Florida Program for Shark Research who led the new study published in the journal Plos One, said the wide-ranging study is good news for shark conservation.
WHY IS THERE CONFUSION ON GREAT WHITE SHARK NUMBERS?
White sharks can be notoriously difficult to count. They are highly mobile and migratory and group themselves by age, sex and size.
Unlike marine mammals, they do not surface to breathe. Some gather at aggregation sites to dine on seals while others stay at sea, dining on fish.
Most tagging studies use photographic tags - pictures of unique markings, such as nicks on fins or scars - and those markings can change over time.
Population estimates, however, are important to conservation. Sharks are sensitive to overfishing, both as unintentional catches for fisherman seeking other fish and as targets for sport or in areas where shark meat is a delicacy.
White sharks are protected in many areas internationally, including the west coast of the United States, but because they swim in and out of jurisdictions they are still vulnerable, and the older study raised concerns.
Scientists reanalysed three-year-old research that indicated white shark numbers in the Eastern North Pacific were alarmingly low, with only 219 counted at two sites.
That study triggered petitions to list white sharks as endangered.
'The good news is that white sharks are returning to levels of abundance,' said Burgess, also a co-founder of the Shark Specialist Group of the International Union for the Conservation of Nature.
'White sharks are the largest and most charismatic of the predator sharks, and the poster child for sharks and the oceans in general.
'If something is wrong with the largest, most powerful group in the sea, then something is wrong with the sea, so it's a relief to find they're in good shape.'
Great White Sharks are now listed as 'vulnerable' on the IUCN Red List rather than 'endangered'.
Burgess credits the growth in sharks to 40 years of U.S. federal protections for marine mammals that sharks feed on, especially sea lions and seals.
In addition, white sharks have been protected as a prohibited species, making it illegal to bring a great white to dock.
Burgess said he and some other shark experts 'did a double take' when the Stanford researchers calculated the population of adult and near-adult great whites along the central California coast at 219.
The Burgess study claims that the Stanford researchers then claimed inappropriately the 219 count represented half of the adult and near-adult population in the entire Eastern North Pacific, which runs from Alaska down to Central America.
The National Marine Fisheries Service (NMFS) was petitioned to add white sharks to the endangered species list but declined, based on its own research, bolstered by a preview copy of the study by the international team, said Heidi Dewar, a fisheries research biologist.
NMFS estimated the Eastern North Pacific population at about 3,000 sharks.
'We determined there were enough animals that there was a low to very low risk of extinction, and in fact, most developments suggest an increasing population,' Dewar said.
Great White Sharks can be notoriously difficult to track because they are highly mobile and migratory, being found in oceans throughout the world as shown in this distribution map. They also group themselves by age, sex and size, making them difficult to count accurately
In this study scientists re-analysed three-year-old research that indicated white shark numbers in the Eastern North Pacific were alarmingly low, with only 219 counted at two sites. They found that the total population is most likely at least an order of magnitude higher at well over 2,000
Burgess and his colleagues assembled a 10-member team with expertise in all facets of shark biology: demography, population dynamics, life history, tagging and movements, fishery biology and conservation, and mathematical modeling.
The team has studied sharks from Florida to California, Alaska to Hawaii and around the globe.
For their reanalysis, the international team examined the two aggregation sites where the earlier count was obtained, the Farallon Islands and Tomales Point, which attract seals and the sharks that feed on them.
They found that the sub-populations at both sites were so fluid, with both resident and transient sharks, that it would not be possible to extrapolate a total population number.
To get a better picture of the white shark population in the Eastern North Pacific, the team decided to examine several other known aggregation sites, from Mexico into British Columbia and Alaska.
The team also conducted a demographic analysis to account for all life stages for the sharks at Farallon Islands and Tomales Point and found that the total population is most likely at least an order of magnitude higher - rather than just over 200 sharks there likely were well over 2,000.
For their reanalysis the team examined the two aggregation sites where the earlier count was obtained, the Farallon Islands and Tomales Point (shown). They found that the sub-populations at both sites were so fluid that it would not be possible to extrapolate a total population number, so they examined other known sites
There has been much controversy regarding the accidental catching of sharks, known as 'bycatch'. IT is now illegal to bring white sharks to dock and measures to try and improve shark numbers are seemingly working. Pictured is a Great White Shark caught by fisherman in a boat close to Bodega Bay in California in March 2011
'The listing of a species as "endangered" places substantial demands on governments,' Burgess continued.
'Listing species that are not under the threat of biological extinction diverts resources away from species genuinely at risk.
'We want to use our resources for the neediest species.'
The earlier study also compared shark population numbers with other so-called apex predators (those at the top of their food chain), such as polar bears and killer whales.
That study, however, ignored the differences in the community structures for those three species and the fact that polar bears and whales, as mammals, are easier to count.
'That we found these sharks are doing OK, better than OK, is a real positive in light of the fact that other shark populations are not necessarily doing as well,' said Burgess.
'We hope others can take our results and use them as a positive starting point for additional investigation.'
And he added: 'This is a real pleasure for us in the biology business to be talking about because it's a success story.'
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