As fishermen and scientists chase tropical tuna and marlin that have drifted into San Diego’s unusually warm waters during the past two years, they’ve encountered something else they’ve never seen: flotillas of loggerhead sea turtles bobbing off the California coast.

“This is the first account we’ve seen of so many loggerhead turtles in the history of scientific record,” said Jeff Seminoff, head of the marine turtle ecology and assessment program at the National Oceanic and Atmospheric Administration’s Southwest Fisheries Science Center in La Jolla.