The volume of shipments through the St. Lawrence Seaway will increase by about seven per cent this year compared with 2010, the system's Canadian operator predicted Tuesday.

St. Lawrence Seaway Management Corporation CEO Terence Bowles said cargo shipments are expected to reach 39.1 million tonnes.

The corporation shares operating responsibility for the system with its American counterpart, the U.S. Saint Lawrence Seaway Development Corporation.

The seaway officially opened its 53rd navigation season Tuesday.

"Transportation of raw materials serves as a bellwether for the economy as a whole, and despite volatile global economic conditions, we have reason to be cautiously optimistic regarding our various market segments" Bowles said.

"Projections for the 2011 season foresee continued strength in the traditional staple cargoes of grain and iron ore. Shipments of road salt are projected to increase to replenish inventories depleted over a challenging winter season," he said.

"Project cargo is pegged to rise due in part to continued activity in the oilsands."

Algoma Central Corporation, Canada Steamship Lines and the Canadian Wheat Board have all announced plans to spend a combined $350 million on building new vessels for their fleets.

Since opening in 1959, over 2.5 billion tonnes of cargo worth over $375 billion has moved through the seaway.