After three weeks of debate, 13 nations including the United States and the Soviet Union have agreed on the first move toward an orderly exploitation of the vast marine resources of the southern seas around Antarctica.

The Antarctic treaty powers have agreed to push for an international convention governing fishing there before the end of next year.

The tight timetables, by the usual standards of diplomacy, reflects a determination to achieve voluntary restraint on catches of the protein-rich, shrimp-like krifl as quickly as possible. The Japanese and Soviet already fish krill commercially and three more nations have experimental programs.

A preparatory meeting is to be held in Australia in February or March to draw up a draft and decide what other nations and international organizations will be invited to take part.

The Krill has been described as the world's last great untapped food source. Some experts say there are enough schools of Krill in Antarctica to double the world's edible fish catch.

U.S. Deputy Assistant Secretary of State Robert C. Brewster said the "krill agreement," reached at the ninth consultative meeting of the Antarctic treaty powers ending last night, is "unique" and an encouraging development for environmentalists.

For the first time, international controls may be put in place before a species is overexploited or hunted to the verge of extinction.

The London meeting concentrated on the living resources issue because it seemed more immediate and easier to solve than the difficulties involved with exploitation of mineral resources - which involves overlapping territorial claims.

After hearing from a committee of experts, the conference decided to put off mineral exploitation. The technical committee recommended against exploiting the land and seabed minerals for at least 15 years.

British conference chairman George Hall said, "There is no proof that commercially significant hydeocarbon or other mineral resources occur on land or the continental margins of Antarctica."

A U.S. document has asserted that the Antarctic shelf "could contain potentially recoverable oil in the order of magnitude of tens of billions of gallons."

Some have attributed the playing down of such and the Vritish desire to keep up the price of North Sea oil than to the difficulty of bringing it ashore.

A s with the proposed living resources convention, the hope is to get international regulations in force in time to prevent a free-for-all and pollution in the one part of the world that man's activities have not already fouled.

A meeting is to be held in Washington in 1978-79 to consider the legal and political implications of getting at the minerals believed to be there. The report would be considered at the 10th consultative meeting of the treaty powers in Washington in 1979.

The Antarctic treaty powers are: Argentina, Australia, Belgium, Chile, France, Japan, New Zealand, Norway, South Africa, Britain, the United States, the Soviet Union. Poland has recently been admitted. The 1959 treaty is of indefinite deration but is to be given a full review in 1989.