Share this article American and Canadian ports in the Great Lakes-St. Lawrence Seaway System have marked a strong start to the 2021 navigation season with total tonnage up nearly 4 percent, according to the Great Lakes Seaway Partnership representing ports on both sides of the border. The 2021 season, which opened March 22 with the opening of the St. Lawrence Seaway, has had 416 vessel transits totaling a little over 4 million metric tons through April, representing a 3.7 percent increase compared to shipments through the same period last year. Through April, iron ore shipments through the Great Lakes-St. Lawrence Seaway reached 703,000 metric tons, nearly a 7% increase compared to shipments of iron ore during the same time in 2020.