Historically, gray whales (Esrichtiius robustus) inhabited the North Pacific, North Atlantic and Arctic Oceans. The Atlantic population had disappeared by the end of the 18th century, likely due at least in part to hunting pressure. In the North Pacific, gray whales historically migrated along both the North American and East Asian coasts, with feeding areas centered in the Okhotsk and Bering Seas and wintering grounds centered in subtropical lagoons and bays in Mexico and southern China.
Gray whales in the Pacific were seriously over-exploited by commercial whaling in the 19th and 20th centuries. In fact, in the west they had become so scarce in waters off China, Japan, Korea and Russia that the population there (commonly referred to as “western” gray whales) was suspected to be extinct by the 1960s. However, small numbers were observed off north-eastern Sakhalin Island (Russia) in the 1990s and since then a slow increase in numbers has been documented. Some 170-180 gray whales now feed intensively on the Sakhalin feeding grounds every summer and autumn and there are occasional reports from elsewhere in the Russian Far East, Japan and China.
The “eastern” population of gray whales that migrates between Mexico and Alaska recovered substantially after being protected from commercial whaling and it now numbers about 20,000 individuals.