04/02/2015 03:14 EDT | Updated 06/02/2015 05:59 EDT

Great Lakes ice coverage causes minor shipping delays

For the second spring in a row, the amount of ice on the Great Lakes is higher than normal, according to environmental researchers.

But the commercial fishing and shipping season has been only slightly delayed, and higher lake levels could be beneficial for recreational boaters.

According to data from the Great Lakes Environmental Research Laboratory (GLERL) of the National Ocean and Atmospheric Administration in the U.S., lakes Superior, Michigan, Huron, Erie and Ontario collectively had 57.6 per cent ice coverage on March 25.

While the ice coverage is less than the 73.5 per cent it was this time last year, it's still well above average, said George Leshkevich, a scientist with GLERL in Ann Arbor, Mich.

The normal amount of ice coverage for this time of year is 19 per cent, according to Denis Dubé, senior ice forecaster with Canadian Ice Services, a government agency.

Shipping delayed slightly

Heavy ice coverage that stays on the Great Lakes into spring can make lake travel difficult, if not impossible, and can postpone the delivery of cargo such as grain, coal and manufactured goods.

While the ice cover has stayed longer than usual, it's starting to break up, which is a good sign for ports on the Great Lakes. The St. Lawrence Seaway opened today, with the CWB Marquis being the first ship to leave the Port of Montreal.

Guy Jarvis, harbour master at the Thunder Bay Port Authority, the end point for many Great Lakes ships, said that while transport has been affected by the ice cover, "delaying systems by a week isn't a huge hurdle."

Jarvis admits that the ice coverage has created "extreme challenges," but said the port learned from last year, and brought in icebreakers earlier. "Experience makes a big difference," he said.

The Icebreaker Pierre Radisson arrived April 1 to open up the entrances to the Thunder Bay harbour.

Welland Canal, which connects Lake Ontario and Lake Erie, opened Thursday to allow ship transit.

Jarvis expects the first vessels from Lake Ontario to arrive in Thunder Bay at the end of next week, although it depends on how well the ice breaks up in Lake Erie.

According to GLERL data on the Great Lakes for March 25, Lake Erie had the most ice coverage, at 87.8 per cent, while Lake Ontario had the least, at 24.5 per cent.

Loss of Lent market for fisheries

The extended ice coverage has also delayed commercial fisheries, which had hoped to start work in early March.

March is an important month for fisheries, since fish is often eaten on Friday nights during Lent, which started Feb. 18 and ended April 2 this year.

The fact that Easter comes earlier this year means an even bigger loss for fisheries, according to Jane Graham, executive director for the Ontario Commercial Fisheries' Association.

Even so, she says the melting ice is a positive sign.

"As the ice is clearing up and moving out, there are more and more fisherman getting out there," Graham said.

Water levels above average

This year's ice coverage may have an upside for fishers, ship captains and cottagers in that it could maintain, if not increase, above-average water levels on the Great Lakes.

Researchers suspect that heavy ice cover has led to decreased evaporation, which has raised lake levels.

"We do believe that the past two winters' ice cover has played a role and that there has been diminished evaporation," said Drew Gronewold, a hydrologist at GLERL.

Higher water levels allow vessels to transport heavier cargo and make navigating and docking easier for fishers and recreational boaters.

Regardless of the extent to which ice coverage affects lake levels, the 15-year period of below-average water levels on lakes Superior, Michigan and Huron has ended. According to the Great Lakes Water Level Dashboard on GLERL's website, those lakes are projected to have above-average levels in the next six months. Lake Erie is also forecasted to have above-average water levels, but Lake Ontario is looking at normal levels.

The bad news for cottagers is that their first swim of the season may be chillier than usual.

"If we get a cooler summer and the ice does last into April or even early May … then the water temperature could remain below normal," Leshkevich said.

Dubé expects all ice on the Great Lakes to be melted by mid-May.