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The population of great white sharks lurking off the Northern California coast grew between 2011 and 2018, according to new research.
A study estimated that 266 great whites were living in the so-called Red Triangle area, which reaches roughly from Big Sur to the Farallon Islands to Bodega Bay in 2018 — up from 219 counted in 2011. With a large population of elephant seals, harbor seals, sea lions, sea otters and other marine mammals, the area lures great white sharks.
The study, conducted by researchers from Stanford University and the Monterey Bay Aquarium and others, tracked and photographed the sharks from overhead and underwater from 2011 to 2018 to estimate their populations.
About 60% of the great white sharks tallied in 2018 were males and they were about 12.4 feet long; females were about two feet longer.
The slight growth in the great white shark population is likely due to three factors, the study found:
• • A California law prohibiting fishing for great white sharks in state waters, which extend three miles off the coast in 1994. Federal laws restricting but not eliminating shark fishing were enacted in 2000 and 2010.
• Gill-netting was banned in California in 1990, likely saving the lives of many juvenile sharks.
• The Marine Mammal Protection Act of 1972 banned the fishing of seals, a popular food for great whites, causing their populations to soar.
“Taken together, these protections may influence the prospect for population increase of this important marine predator,” the study said.
But sharks still need protections, especially far off the coast, where fewer fishing restrictions exist.
Researchers, working at Año Nuevo Island off the San Mateo County coast, Southeast Farallon Island and Tomales Point, used boats dragging a seal dummy as well as the scent of local marine mammals to help attract sharks during peak periods of visitation. They spent 2,587 hours collecting video recordings and photographs of their white dorsal fins, which have a unique appearance, similar to a fingerprint.
Given the vulnerable life history traits of white sharks,” the study concluded, “insuring their future will take a continued effort to monitor populations and identify potential future threats such as climate change and unregulated high-seas fisheries.”
Michael Cabanatuan is a San Francisco Chronicle staff writer. Email: This email address is being protected from spambots. You need JavaScript enabled to view it. Twitter: @ctuan