Ottawa — Canadian authorities are in a state of stunned confusion as they await President Reagan's visit here today. The confusion comes on the heels of a series of unexpected US policy decisions on Canadian-american issues.
Many of the announcements coming out of Washington in recent days bear directly on questions Prime Minister Pierre Trudeau's administration plans to discuss with Mr. Reagan. The two-day visit, March 10-11, is the first by a US president to Canada since 1972.
The US decisions that now have Ottawa wondering what to expect include:
* The shelving of a substantial portion of an East Coast fisheries treaty. This agreement, signed by Canadian and US officials almost two years ago, has gone unratified by the US Senate, and the Canadian government had considered it the most important item on the agenda for the Reagan-Trudeau talks.
On March 6 President Reagan said he was withdrawing from the Senate the portion of the treaty dealing with East Coast fish allocation. He said an ocean boundaries dispute covered by another section of the agreement should be turned over for arbitration to the International Court of Justice at the Hague.
In reaction, Canadian External Affairs Minister Mark McGuigan issued a statement expressing "disappointment and regret" over the US move. He said Parliament, fishermen, and other Canadians were stunned by the announcement.
* Indications the Reagan administration will give additional funding to the controversial Garrison diversion project in North Dakota.
Earlier, all parties in the Canadian House of Commons joined in criticism of the new US government for approving the spending of an extra $4 million on the Garrison project. Canadians fear this water project will cause contamination of rivers in Manitoba.
* The latest US moves at the United Nations to stall or even throw out the Law of the Sea Treaty, which was expected to be concluded in the session beginning March 9.
Last week, Secretary of State Alexander M. Haig Jr. instructed US negotiators not to conclude the treaty until certain sections had been reviewed. Then, calling for a "clean break" with the past, the top US negotiators were abruptly fired March 8.
Canada is one of 152 nations that has spent seven years in consultations to draw up a multilateral agreement governing joint use of the world's oceans.
Ottawa is also puzzled by reports from Washington last week that the Reagan administration may back away from the previous US administration's support for construction of a Canada-Us northern natural gas pipeline.
Prospects for the US president's visit are a matter of guesswork here in the wake of the recent US announcements. There was a general feeling that the decisions, by seeming to disregard Canada's concerns, had put Prime Minister Trudeau in a difficult position prior to the conference.
Many observers doubted that, under the circumstances, the two leaders could easily overcome their deep political differences to achieve a cordial and useful meeting. Mr. Trudeau is a Liberal, a social democrat who has not hesitated in the past to use government intervention to control aspects of the country's private sector.
As America's largest trading partner (two-way trade in 1980 reached $94 billion [Canadian]), Canada has an economy greatly dependent on the success of Mr. Reagan's new fiscal program. A good deal of the 27- hour visit is expected to be devoted to an explanation of the US economic plan.
Another bilateral issue is energy. Mr. Reagan is expected to express reservations about the Trudeau administration's so-called National Energy Program, under which the Liberal Party wants to reduce foreign control of the Canadian oil and gas industry to 50 percent by 1990 from the current level of 70 percent.