The screen on my sonar unit showed an abundance of both baitfish and larger gamefish.

Pointing this out to my partner Sid Brown, he glanced at the display and remarked that one of us should be getting a fish soon. A few moments later, two of the four rods that were trolling baits 100-odd feet behind the boat bent under the strain of the hooked fish.

As so often happens when trolling, a bit of mayhem followed. But when it ended, two quality-sized largemouth bass were in the boat.

We weren’t targeting bass — walleyes and crappies were the intended species — but I’m not so big-headed to dismiss these fish simply because trolling is not a tactic typically associated with taking them.

I recall an article from an old Fishing Facts magazine —circa mid 1980s — when author Spence Petros detailed trolling as a tactic to quickly learn new water. He didn’t discriminate regarding species.

As I recall, he suggested trolling to rapidly get a handle on how structure was laid out aswell as how fish relate to such. Lessons gleaned from these efforts would then present casting options.

The water Sid and I were fishing — Keystone Lake — is quite familiar to me, having fished it for well over 30 years. However, fish location within that lake (or any lake, for that matter) is a constantly changing factor, driven largely but food sources.

When you think about it, fish only have three concerns in life: to reproduce, eat, and not be eaten themselves.

The first is only of concern during the springtime for the region’s common warmwater/coolwater species. By late summer, it’s the second item that often drives gamefish location. In a lake such as Keystone — which has a food-fish menu that includes emerald shiners, rainbow smelt, juvenile panfish, and various minnow, crustaceans, and insects — it’s likely gamefish will be keying in on multiple forage sources.

In the scenario described at the outset, huge schools of bait appeared in the general vicinity of both a creek channel and submerged wood in 20 to 22 feet or water.

I suspect they were young-of-the-year bluegills, crappies, and/or yellow perch. The bass were keyed in on the bait, as we ended up catching a dozen largemouth and smallmouth bass in about an hour.

The trolling advantage allowed us to quickly cover the water as we moved along at around 2.25 mph. When you’re trolling, your eyes tend to be zeroed in on the sonar screen like a video playing out in front of you.

Structure, cover, baitfish, gamefish, are all presented in a format that’s much easier to interpret than from a stationary casting position. The next time I return to Keystone, it will be with casting baits that I can ply these same areas with, in the hope the baitfish and bass are still there.

Our most productive trolling lures were Rapala Scatter Rap minnows and Storm Hot-n-Tots.The minnow baits were fished with about 110 feet of leadcore line, which put them down around 20 feet of depth.

The Hot-n-Tots were fished about 120 feet behind the boat on 30-pound test braided line, which put them about 15 feet down. Off Shore inline planer boards, with Church Tackle “Lock Jaw Clip” releases, spread these baits away from the boat.

Jeff Knapp is an outdoors columnist for the Butler Eagle