By Jonathan Allen
NEW YORK (Reuters) - The number of great white sharks off the U.S. Atlantic Coast appears to have increased since the early 1990s after conservation measures were introduced to halt their decline, a U.S. government scientist said on Saturday.
Scientists for the National Marine Fisheries Service presented the findings in a study published this month in the PLOS ONE online journal.
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Tobey Curtis, one of the government scientists who worked on the study, said in an interview his team could only capture trends in shark abundance and the study could not be used to estimate the total number of sharks in the Atlantic's northwest region, which extends from the U.S. East Coast.
"We don't know what portion of the total population we're documenting," he said.
But Curtis said the findings suggested an "optimistic outlook" for the recovery of the species, which is an apex predator and one of the largest fish in the oceans. The study's authors described their study as based on the largest white shark dataset yet compiled from the region.
The findings were based on data stretching back about 200 years, including population surveys, fishermen's logs and newspaper clippings recording sightings of the elusive creatures.
Extrapolating from the varied data, the scientists said that for much of the 1970s and 1980s the abundance of sharks in the northwest Atlantic was on average about 70 percent lower than in 1961, the year they chose to use as a benchmark.
They speculated the decline was caused by a growing commercial shark fishing industry, which harvested their fins and jaws for use in food and folk medicine.
The decline was reversed in the 1990s after conservation measures were introduced, including a 1997 federal law banning the hunting of great white sharks.
"Since protections were put in place, the population appears to have started recovering," Curtis said.
In 2009, the most recent year they studied, the abundance of sharks was 31 percent lower than it was in 1961, Curtis said.
In a separate paper also published in PLOS ONE this month, researchers found the great white shark population is likely growing in the Pacific Ocean off the coast of California.
The group, led by George Burgess, director of the Florida Program for Shark Research, pegged the entire population of white sharks along the California coast at more than 2,000 and likely rising.
The study's authors challenged the conclusions of a 2011 Stanford University study that found alarming low numbers of the predators off the central California coast.
Burgess also was involved in the study of shark abundance in the Atlantic Ocean.
(Reporting by Jonathan Allen; Editing by Alex Dobuzinskis and Lisa Shumaker)