On Oct. 16, a team of researchers hauled aboard a 1,419-pound male leatherback sea turtle about five miles from Pillar Point Harbor, south of Devil’s Slide. It was an unlikely encounter with a rapidly dwindling endangered species.
The group of scientists from the National Marine Fisheries Service and the nonprofit organization Upwell was there to tag leatherbacks to track their movements and reduce the risk of entanglement in fishing gear.
The data this team gathered, along with numerous aerial surveys, informs the California Department of Fish and Wildlife and the Dungeness Crab Fishing Gear Working Group on the risk of whale and turtle entanglement during crab season. Based on the data gathered over the last few months, the state delayed the start of crab Dungeness crab season in early November throughout the Bay Area for the third consecutive year.
The state said at least five leatherback sea turtles were found by aerial and
marine surveys in the Bay Area’s two fishing zones, along with 48 humpback whales. As rare as these turtles are,
something seemed familiar to NOAA Fisheries researcher Scott Benson. Specifically, the large bumps on the rear part of its carapace, the oily, leather-like exoskeleton, that Benson believed was likely a healed injury resulting from striking a ship propeller.
It turned out “Bumpy,” as the researchers appropriately named him, had been tagged by Benson just a few miles away near Montara almost five years ago, in September 2016.
The second encounter with Bumpy marks only the second time that a previously tagged male Pacific leatherback had been encountered and captured again in the foraging grounds. It also was the closest an acoustic tag has been attached on any leatherback in the California Current Ecosystem, what scientists call the highly productive and nutrient-rich coastal water in the northeastern Pacific Ocean.
The acoustic tags, which tend to last longer than satellite tags, will transmit data to receivers on nearby buoys periodically when Bumpy swims by. Western Pacific leatherbacks hatch in tropical waters of Indonesia, Solomon Islands and Papua New Guinea before migrating across the Pacific Ocean to feed on the west coast of North America.
“While leatherbacks can reach up to 2,000 pounds, it’s incredibly rare to encounter one so large in the foraging grounds off the coast of Central California, or anywhere, for that matter,” Upwell Executive Director George Shillinger said in a prepared statement. “Additionally, most tagging operations take place at nesting beaches with females only, so it’s extraordinary to have the opportunity to tag a male leatherback, especially one of this size.”
Leatherbacks have been swimming since the time of the dinosaurs. They’re the largest turtles in the world and can grow to be up to six feet long and 2,000 pounds. Though leatherbacks have been listed as federally endangered since 1973, California only last month added its west Pacific subspecies to its endangered species list and guaranteed its protection under the state’s Endangered Species Act. The National Oceanic and Atmospheric Administration states that the biggest threats to leatherbacks include bycatch in fishing gear, vessel strikes, climate change and egg harvesting.
Because these turtles are so elusive, estimates vary on how many leatherbacks remain worldwide. The U.S. Fish and Wildlife Service estimated there were 34,500 females nesting annually across the globe in 1995, a dramatic decline from the 115,000 estimated in 1980. NOAA Fisheries estimates the global population has declined 40 percent over the past three generations.
But for western Pacific leatherbacks, the situation is much more dire. According to a report in “Global Ecology and Conservation” coauthored by Benson, western Pacific leatherbacks foraging in California have declined 80 percent in the last 30 years. The Center for Biological Diversity estimates about 50 sea turtles come to
California each year, a sharp drop compared to about 178 turtles in the 1990s. Despite their small numbers, leatherbacks roam across the world and can be found from western Africa to the southernmost tip of New Zealand and in the Arctic Circle.