The gray whale is known to be one of the world's most endangered creatures. Only 35 of the 130 remaining gray whales are thought to be breeding females.
The whale is listed as "critically endangered" by Russia and is on the International Union for the Conservation of Nature's red list of endangered species.
The suspension of seismic work by Sakhalin Energy, which is backed by Shell and Gasprom, might mean the whales can move in-shore, feed and breed.
However, campaigners pointed out that other oil and gas firms working in the region, including BP. Exxon and Rosneft, were still planning to carry out seismic work in 2009.
Two Pacific Ocean populations of the Gray Whale exist: one of not more than 300 individuals whose migratory route is unknown but presumed to be between the Sea of Okhotsk and southern Korea, and a larger one with a population between 20,000 and 22,000 individuals in the Eastern Pacific traveling between the waters off Alaska and the Baja California.