Story by Lauren Williams, OC Register.
Like any teenager, adolescent great white sharks don’t like to hang out with their parents.
While many mature great whites spend much of their time feasting on seals in popular feeding areas like the central California coast, their offspring spend much of their time dining on fish in Southern California.
Researchers behind a new report say that this habit, in part, caused previous research to severely undercount the size of great white shark populations, creating panic among conservationists that the sharks were dwindling to near extinction.
“When you make a model, you obviously need to tailor it to what is known about the animals involved,” said George Burgess, the director of the Florida Program for Shark Research and the newest study’s lead author. “These animals are capable of, and often do, make long-distance migrations out of the area.”
In California, at least, the great white shark population is healthy, according to the study published Monday in the online scientific journal PLOS One. A team of 10 scientists, including a Cal State Long Beach professor, found that the population of great whites along the California coastline is about 2,400.
A 2011 scientific study said that the population of great white sharks in a much larger area, from Alaska to Baja California, had dwindled to 438. That spurred an effort to put the aquatic predators on the list of endangered species.
That study used photos to identify unique markings on great whites off coastal Central California when the sharks’ fins would surface, essentially “tagging” the sharks. Scientists then searched previous photos for those identifying characteristics to track the population.
The study was published in 2011 in Biology Letters, a biological research publication.
Burgess said one of the flaws with the earlier research is that it looked at the group of sharks feeding in the area as a closed population, although great whites are mobile.
In the latest study, researchers used data from the same places as the earlier study but used a demographic model that took into account wandering sharks.
Tracking the population of great white sharks is complicated by the fact that they migrate thousands of miles, are segregated by sex, age and size, and don’t surface to breathe.
“They’re automatically hard to observe,” said the study’s co-author, Chris Lowe, a Cal State Long Beach professor who runs the university’s Sharklab research program. “They’re highly mobile.”
Because the earlier population count relied on seeing the sharks and photographing them, its results may have been skewed, Lowe said.
Researching great whites is further complicated because the shark is naturally stealthy as a predator of nimble, fast-moving animals, like sea lions. Scientists previously characterized great whites as coastal sharks, but newer technology like satellite transmitters show that great whites travel thousands of miles in the Pacific Ocean, Lowe said.
“We’ve learned a lot in the last 20 years, but it’s only scratching the surface,” Lowe said.