STRIKE THREAT, LOWER TRAFFIC MAR SEAWAY OPENING The St. Lawrence Seaway, set to reopen March 31 after the winter, faces another tough year because of depressed traffic levels and the possibility of the first strike in 20 years on the Great Lakes, seaway officials said. Depressed grain exports, rising costs, and competing modes of transportation are all expected to result in only a marginal increase over last year's traffic levels -- and revenues -- on the 2,300 mile waterway, officials said. In 1986, a season that ran from April 3 to December 27, the seaway moved 37.6 mln metric tons of freight between Montreal and Lake Ontario and 41.6 mln tons on the Welland Canal, linking Lake Erie and Lake Ontario. By comparison, in 1985 about 37 mln tons of cargo traveled through the Montreal-Lake Ontario section and 42 mln through the eight-lock canal. The waterway is expected to lose 9-10 mln Canadian dlrs this year, about the same as the estimated deficit for fiscal 1986-87 ending March 31, said William Blair, an executive member of Canada's St Lawrence Seaway Authority. The seaway moves about one-half of Canada's exported grain. Those exports of the single most important commodity carried on the waterway have been depressed by world surpluses. The Seafarers' International Union, which represents about 2,300 workers on the Great Lakes and the ocean coasts, has said it will likely go on strike this spring to protest employers' demands for wage rollbacks and other concessions. "It's 99.9 pct (certain)--I guarantee you a strike," Roman Gralewicz, head of the Seafarers' Canadian branch, has said. The Canadian government has called in a labor conciliator to try to hammer out a contract agreement between the two sides. The seaway authority said a walkout tying up ships on the Great Lakes would badly hurt traffic. "We haven't had a strike on the seaway for years...a prolonged strike would have a disasterous effect," Seaway Authority spokeswoman Gay Hemsley said. "These are the heaviest contract talks in the history of the St Lawrence Seaway," George Miller, vice-president of the Canadian Lake Carriers Association, an association of major Canadian shipping companies, said recently. The workers' current contract expires May 31. The association said it is asking for a five per cent cut in wages for the next three years, reduced crew levels and the power to restructure crew dispatching. The association said its members recorded about a 6 mln dlrs (U.S.) loss in each of 1985 and 1986 due to lower traffic and freight rates and increasing competition. The seaway said 1985 was its worst year in two decades. Hemsley said the seaway authority plans to raise tolls on the Welland Canal by eight pct this year, compared to last year's 15 pct rise, while maintaining a freeze on tolls throughout the rest of the waterway. Canada is responsible for 13 of the seaway's 15 locks and about 85 pct of its revenues and maintenance costs. "We may see and hope for a steady upward climb...but we won't see a major increase for a number of years," Hemsley said. A Canada-U.S. delegation to promote the seaway to shippers in Western Europe should result in some increased traffic this season but the full benefits won't be felt for several years, Blair said.