December 29, 2020 — Once hunted to the brink of extinction for their luxuriant pelts, California sea otters rebounded after protections were put in place in 1911. Their population grew steadily for much of the last century, but now the still threatened species is stuck at about 3,000 otters. The problem is that they are boxed in at both ends of their current range, along the state’s central coast, by a sharp (and so far unexplained) rise in shark attacks. Hoping to reintroduce breeding populations elsewhere in the otters’ historical range, wildlife managers have been looking at certain coastal estuaries, which are sheltered pockets of water.
It turns out that the largest estuary on the West Coast—San Francisco Bay—could potentially provide an excellent home for sea otters, despite being in the middle of a major urban area, according to a study published last month in PeerJ.
“I was surprised,” says lead study author Jane Rudebusch, a spatial ecologist at San Francisco State University’s Estuary & Ocean Science Center. “The bay is intensely urbanized. You can tell it’s a busy place just by looking at it.” Tanker ships deliver crude oil to shoreline refineries every day, and high-speed commuter ferries constantly zoom between San Francisco, Oakland and other waterfront cities at up to 50 miles per hour. Sediment in parts of the bay is laced with methylmercury and polychlorinated biphenyls, toxic chemicals that accumulate in the clams, crabs and other animals that sea otters eat.