Fish often concentrate in a specific stratum of the water column, held there by food, temperature, and other conditions they find to their liking. This can challenge anglers who want to keep their trolling baits or lures in the zone. While lead-core line is one way to get offerings to run deep, downriggers are a more precise and controlled way to troll when fish are holding at a specific depth.
Follow Your Fish Finder
Use your fish finder to look for schools of bait and fish, as well as thermoclines that often mark as a steady line between the surface and the bottom. Any of these can signal the depth to set your lines. Monitor the screen to make sure your downrigger weights are far enough above structure, trees or other obstacles to avoid snagging.
Test the Waters
Until you figure out at which level the fish are holding, run your downriggers at different depths. You can also stagger-stack two or more trolling lines on each downrigger by using adjustable line releases that clip onto the downrigger cable. Once you find a pattern of strikes at a particular depth zone, adjust all your gear to focus the effort in this area.
Consider the Conditions
Don't rely solely on the downrigger's depth gauge, because boat speed and the speed/direction of the current can affect the actual trolling depth of your lure or bait. You can often observe the actual running depth of your gear on the fish-finder display and raise or lower the downrigger to get into the strike zone.