The Monterey Bay Aquarium states, "By 1911, when sea otters gained protection under international treaty, a small group of perhaps 50 otters survived along the remote Big Sur coast. Since then, they've slowly expanded their range and grown in number to nearly 2,800 [in California]. As of 2012, their range extends from south of Half Moon Bay in the north to south of Point Conception in the south; only a small part of their historic range."
Meanwhile, Defenders of Wildlife states, "There are between 64,600 and 77,300 northern sea otters residing in Alaska, Canada and Washington. There are approximately 15,000 in Russia and less than a dozen in Japan."
The sea otter is still struggling to make a come back, and continues to be listed as an endangered species.