Tuesday | December 12, 2017
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White sharks not quite as rare anymore

White sharks are still a relatively rare occurrence in Hawaii’s waters, but a new study shows the animals are showing up here year-round.

That’s a new finding, says Kevin Weng, manager of the Pelagic Fisheries Research Program, a collaboration between the University of Hawaii and NOAA’s Pacific Islands Fisheries Science Center. He said it contradicts studies of white shark populations using satellite tracking systems. That may mean the tracking systems, which focus on white shark populations near seal colonies along North America’s western coast, are missing segments of the white shark population.

Weng said the study doesn’t answer a number of questions, including why the sharks migrate here.

“We don’t have a good understanding of that presently,” he said. “There aren’t any patterns that give us clues.”

The sharks that do make it to Hawaii are both male and female, some sexually mature and others not old enough to be sexually mature, he said. One thing scientists have observed — the white sharks observed here are all too large to be shark pups and scientists have no evidence that sharks are coming here to deliver pups.

“There’s no evidence that single animals are spending the whole year here,” Weng added.

The research, compiled by Weng and the Department of Land and Natural Resources’ Division of Aquatic Resources, was published in the Journal of Marine Biology. Weng said they had been compiling information about white sharks using other research, news reports, shark control program catch records, photos and videos, as well as the satellite tracking data.

Weng said misidentification of white sharks in Hawaiian waters is also a problem. He pointed to a shark sighting off Kaena Point in January 2012, in which observers identified the shark as a white shark. It was actually a shortfin mako shark, Weng said.

The study offered a “simple” method to help distinguish between the two species based on the shape of the head.

“Mako sharks have a more acute head shape than white sharks,” a release about the study said. “Since many sightings only obtain photographs of the head, this method should be helpful for situations with limited information and no specimen.”