If you think just throwing a couple of lures out the back and keep the boat moving forwards is all that is involved in trolling for freshwater species than think again.
There are quite a number of factors involved to successfully keep in the zone to catch fish.
Our preference is to work the 15-20 foot mark of a dam or river. The reason for this is that it is normally the depth level that our lures swim at that we prefer to use and you will normally find that this is where the thermocline is, however this can vary with different times of the year and weather.
Before I move forward, a thermocline is the transition zone of water between the surface and the deeper water layer. Normally defined by temperature. It is the temperature change where it decreases rapidly from the top layer to much colder deep water temperature. I have included a photo below. Circled is what the thermocline should look like on your sounder.
The next thing to determine is your trace line. Just because your lure says that it swims at 15foot doesn’t mean that by tying on a 30lb leader that it is going to reach this level. Lighter leader normally means it will travel deeper. 8lb to 10lb is normally enough to prevent scuffing from those larger fish and snags and to swim at your lures desired depth.
Speed is equally important. If you go too slowly then the lures will float up to a shallower depth and if you go too fast then they will dig into the water and go deeper. So just adjusting it to the right speed will see results. We have found using the electric motor in non windy conditions you can keep the boat at a more stable trolling speed between 1.5klm to 1.7klm. Using the engine you either may need to put a droge out to keep you at a slower speed or alternatively keep knocking the motor in and out of gear to remain at a good speed.
A good way to measure this is to watch your sounder. If you are running 15-foot lures and you are digging into the bottom and constantly getting snagged you may need to adjust your speed, lure or leader.
This will give you something to think about next time you decide to throw a few lures out for a troll in the freshwater.