 From 1964 to 1973, the Soviet Union was considered by some the biggest whaling nation in the world.Due to implementation of the International Whaling Commission’s International Observer Scheme in 1973, and the subsequent quotas on catch limits of most species of whales the same year, Soviet whaling began a slow decline during this period and from 1978 to 1980 3 of the 4 remaining whaling fleets were retired, largely due to the outlawing of all pelagic whaling except for minke whales in the Antarctic and due to intervention of anti-whaling groups (the "Dalniy Vostok" fleet was the first ever to be harassed through direct action by anti-whaling groups in 1975).After 1980, only the "Sovetskaya Ukraina" fleet remained, taking only minke whales in Antarctic waters.