Wednesday, August 11, 2010

California's Great White Sharks: expert hints at numbers on the rise

Having spent a good portion of my cinematic time filming the great white sharks of California, particularly those that migrate south to Isla Guadalupe, I was heartened by the news that the local populations of these animals might be showing signs of improvement. With all of the uphill battle issues we are having to deal with regarding ocean conservation, it's nice to to get some possible good news for a change.

Making the rounds of the shark blogs, like SharkDivers', is a recent article from Pete Thomas posted in his Outdoors blog. Pete has had a strong interest in white sharks and has been to Isla Guadalupe several times to see them first hand. He writes of some positive comments from Dr. Chris Lowe, director of the Shark Lab at the California State University Long Beach, and someone who has studied a variety of California elasmobranchs for years, from white sharks to leopard sharks to round stingrays.

Pete writes,
"It almost seems implausible, in an era during which so many species of sharks are overfished and believed to be in decline, that any species could mount a comeback. But considering the changing landscape off California, a comeback and its timing make sense. The ban on fishing for white sharks -- for sport or commercially -- was imposed in 1994. That same year, voters approved a measure outlawing the deployment of gillnets within three miles of the California coast."

According to Dr. Lowe, "So if you add those two things [better fishing regulations and increased numbers of seals and sea lions] together, you've got a restored forage base for the adults and you've got better survivorship of the pups," Lowe said. "So what we think we're seeing from the fishery catch data and some of the other anecdotal pieces, is the actual recovery of the white shark population."

But we're not completely out of the woods yet. White sharks are migratory and do not heed the limits of national or regional ocean borders that might provide a degree of protection. These sharks are still threatened by commercial fisherman in international waters (white sharks are not specifically targeted but are subject to loss as bycatch in gillnets) or by poaching (juvenile white sharks are still being caught and sold in local seafood markets in Ensenada).

"If what we are seeing is truly an increase in the white shark population that would be a relief. Currently we are finding that the total number of adult white sharks along the west coast of North America is much smaller than many people expected," says Salvador Jurgenson, who heads up Stanford University's white shark research at the Hopkins Marine Station.

Many thanks to Pete for his article and hats off to Dr. Lowe and his I've had the opportunity to meet with Chris, filming his "round stingray roundup" where a local high-density population of stingrays are collected, measured and released to monitor their growth and overall health. He and his grad students have also conducted metabolic studies of leopard sharks using the Aquarium of the Pacific, where I was a volunteer dive team leader, as a test bed facility. Some good news - nice way to start the day.

Read Pete Thomas' article.
Top photo: RTSea, Bottom photo: Christy Fisher.

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