Study sees decline of sea turtles in state
The number of leatherback turtles that feed in central California waters has declined by 80% during the last two decades, according to new research released by the National Oceanic and Atmospheric Administration and the Moss Landing Marine Laboratories.
“They’re at risk of extinction in the Pacific Ocean,” said Scott Benson, lead study author and marine ecologist with NOAA.
Benson and his coauthors tracked Pacific leatherback turtles using video cameras, satellite and aerial survey data from 1990 through 2017.
The marine reptile makes an extraordinary migration — every three to five years it swims more than 6,000 miles from its Pacific foraging grounds in Oregon, Washington and California to Western Papa New Guinea. There, leatherbacks nest and lay eggs.
Researchers have long known that on Indonesian shores Pacific leatherback turtle populations are sinking. But Benson and colleagues wanted to investigate if the same was happening at central California coastal feeding areas.
Pacific leatherbacks swim to California to forage a common jellyfish — brown sea nettles — from the Monterey Bay area, north to Point Reyes. Those jellyfish are what sustain the turtles, which can weigh up to 1,300 pounds and measure up to 6 feet in length, Benson said.
“This is a species that has been on the planet for 70 to 80 million years in its present form,” Benson said. “It was around when the dinosaurs were around, it survived the ice ages, meteor strikes. … It’s not a poorly adapted animal.”
But in the last 40 years, its numbers have rapidly declined.
Benson and colleagues documented annually around 128 leatherback turtles feeding off central California from 1990 to 2003. From 2004 to 2017, only 55 leatherbacks a year came to forage.