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Off California's coast, where there's jellyfish, there's leatherback turtles

September 29, 2008 | 11:14 am

Leatherback turtles

Endangered leatherback sea turtles have been spotted again off the Central California coast after a two-year hiatus, drawn by jellyfish swarming the area, the San Francisco Chronicle reports:

The leatherbacks were spotted during a monthlong survey cruise aboard a government research vessel and repeated aircraft observations. Researchers said they were seen diving for meals close to shore and snacking now and then in deeper waters much farther out.

"We're getting a better understanding of the leatherbacks and their coastal habitat here after several years when the population was much lower than usual — and after we observed none at all in 2006," said Scott Benson, chief scientist for the National Oceanic and Atmospheric Administration's leatherback survey mission based in Monterey County at Moss Landing.

Spotters aboard the NOAA Twin Otter aircraft found six leatherbacks "surrounded by miles of jellyfish" — along with humpback whales and large ocean sunfish — off the San Mateo County coast and in the midst of regular cargo shipping lanes leading to and from the Golden Gate.

In one case, a leatherback was observed swimming among the jellyfish only 5 miles west of Benson's home in Moss Landing, he said. Another leatherback that was equipped with a more permanent satellite tag a year ago had returned to the same area this year, apparently after spending the winter a few hundred miles south of Hawaii along what Benson called "Jelly Lane."

Leatherbacks don't eat the jellyfish's transparent globular bells — it's the viciously stinging tentacles they love, and Benson and his colleagues found themselves "covered with stinging jellyfish slime" whenever they hauled any of the turtles aboard, Benson said.

In the last 25 years, more than 90% of the leatherback population has vanished.

According to Michael Milne of the Sea Turtle Restoration Project, an environmental group based in Marin County, the abrupt decrease stems from a variety of reasons: egg-hunters raiding their nests, commercial long-line fisheries whose hooks can ensnare the turtles as "bycatch," and, most recently, the erosion of many nesting beaches because of small rises in the sea level caused by global warming.

The Moss Landing sightings aren't the only ones we've reported off the California coast: Last month, more jellyfish also meant more leatherbacks in Morro Bay. And even Texas has seen an uptick in rare leatherback sea turtle sightings.

— Francisco Vara-Orta

Photo credit: Scott A. Eckert / Widecast

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