DULUTH, Minn. (AP) -

This year's shipping season is getting off to a slow start due to record levels of ice on the Great Lakes after an extremely cold winter.

Some ice on Lake Superior is still several feet thick, and ice breakers are working to carve paths for ships.

Jim Sharrow with the Duluth Seaway Port Authority tells KSTP-TV that even with the help, several fleets have delayed their first sailing until early April.

While the ice is good business for civilians who operate ice breaking tugs, Lake Carriers' Association Vice President Glen Nekvasil tells Minnesota Public Radio News that it's bad for the shipping industry.

Nekvasil says heavy ice has prevented some cargo from being delivered and delayed some trips by several days. The iron ore trade was down 35 percent in January.