Marquette

Lake Superior trolling: temperature, thermocline, and currents

Lake Superior’s enormous volume of cold water warms slowly. As summer develops, warmer surface water forms above the colder depths. The thermocline is the layer between them where temperature drops rapidly, and it generally develops later than on the warmer lower Great Lakes.

Lake trout often occupy cold water beneath this layer, while salmon and steelhead may remain considerably higher. Wind-driven upwelling can bring very cold water toward shore and raise the thermocline quickly. Fish depth and bottom depth can be very different: your target fish may occupy the upper water column over hundreds of feet of water.

Use these temperatures as starting points, then follow bait, sonar marks, and bites. In spring, suitable water may be shallow and close to shore; summer lake trout often move deeper while other species remain higher.

Check currents at lure depth and watch for changes after sustained wind. Review wind, waves, and the forecast before choosing your fishing area.

Common lures and trolling methods

Downriggers and Dipsy divers help place your lures at the depths you want to fish. Downriggers provide controlled depth placement, while divers carry presentations down and away from the boat.

Common presentations include spoons, flasher-and-fly combinations, and meat rigs. Use temperature and bait depth to choose where to start, then adjust lure choice, trolling direction, and speed according to lure action and bites.