MONTEREY — Recent legislation labels leatherback sea turtles as “endangered” under the California Endangered Species Act — the result of a California Fish and Game Commission vote last month.

But while it adds another slab of security for these aquatic reptiles, it won’t wholly revitalize their numbers, said Scott Benson, a biologist with NOAA’s fisheries service in Monterey.

“The safest place in the Pacific Ocean for a leatherback is probably off the West Coast of the United States,” he said, insisting that their populations need more than just U.S. laws to save them.

The legislation pairs with existing federal laws to supply additional protections and awareness for this critically endangered species, said Todd Steiner, the Turtle Island Restoration Network executive director. Specifically, it helps advocate for improved monitoring of state-enforced fisheries, he said.

Leatherback numbers in California have decreased 5.6% on average for the past 28 years, according to a study Benson led in 2020. That adds up to an 80% drop in local leatherback populations, which parallels the losses recorded at the turtles’ nesting sites across the Pacific.

“It doesn’t give me much satisfaction putting another dot on the figure showing that (populations) are still going down,” Benson said. “It doesn’t feel great.”

Western Pacific leatherbacks migrate 5,000 to 6,000 miles from their nesting sites in southeast Asia to California’s cool coastal waters each summer. Monterey Bay is a “hot spot” for the state’s official marine reptile, Steiner said. Here, they feast on jellyfish that help them grow from the size of a cookie to 9-foot-long, two-ton creatures, he said.

But their gigantic flippers can get wrapped around commercial fishing gear, Steiner said. The added weight could drown them if they’re entangled — a fate seldom reported in California, according to Benson.

Fishery observers mitigate these threats in the state by keeping track of what’s caught and discarded by boats and recording interactions with marine life. But Steiner said this coverage could be underreported, not only in California but around the world.

“Many more animals die that then are observed,” he said. “I mean, that’s just the nature of a giant ocean.”

The new decision will put pressure on California to ensure observer coverage at state-regulated fisheries, said Steiner, whose organization paired with the Center for Biological Diversity to catalyze the legislation with a petition.

More state monitoring could never hurt, Benson said, especially considering future aquaculture and wind energy projects in coastal waters. But the most harmful impacts remain outside the U.S., where observer coverage comprises less than 20% of the fisheries that scour the Pacific Ocean. Nest destruction and poaching also induce leatherback population losses, he said.

When it comes down to saving these ancient reptiles, it will take an international effort, Benson said.

“Let’s face it: This is an animal that’s been around for 80 million years. You could not argue it’s poorly adapted,” he said. “It’s been able to survive just about anything, but it seems to be having a hard time handling us.”