An endangered Eastern Pacific green sea turtle, normally found in Mexico, the Galapagos and other warm climes, was recently snagged by salmon fishermen outside the Golden Gate. The turtle, about 2,000 miles off course, was either lost or just exploring new turf, scientists said.

The fishermen took a few pictures of the gentle, 150-pound beast, and — after removing the hook from its underbelly and determining that the turtle seemed unharmed — tossed it back in the ocean and it swam away.

“We see leatherback sea turtles all the time, but we knew this wasn’t a leatherback,” said Roger Thomas, skipper of the Salty Lady fishing boat. “We didn’t know what it was.”

Thomas sent the pictures to scientists at the Turtle Island Restoration Network in Marin, who determined that the visiting creature was a very rare, and very far-flung, green sea turtle.

It was the first they had seen around here, they said.

“That’s really an unusual sighting,” said Todd Steiner, director of the Turtle Island Restoration Network. “But with the warmer water, it’s not surprising that we’re seeing animals venture further north.”

The turtle, found on Sept. 6, looked to either be an adolescent male or a small female, although gauging the age, and sometimes gender, of sea turtles is an inexact science. They tend to live longer than the biologists studying them. The only thing scientists know for sure is that some sea turtles don’t reach sexual maturity until age 50.

Green sea turtles normally live in the Pacific’s warmer latitudes. Their numbers are dwindling because of development along the beaches they use to nest, and because they sometimes become snared in industrial fishing nets and drown.

Climate change has also affected the ancient reptiles. Because temperature determines their gender when they hatch, females vastly outnumber males these days. And the warmer ocean currents tend to take the turtles places they’re not accustomed to going, such as San FranciscoBay.

Water temperatures around the Golden Gate this month are about 65 degrees, about five degrees higher than normal and possibly harkening an El Nino, Steiner said.

The green sea turtle isn’t the only unusual visitor Thomas has seen lately. He’s spotted red-footed and brown boobies at the Farallones, plus some warm-weather albatross.

“We’re seeing all kinds of things,” he said.

Read online at the San Francisco Chronicle.