Stuart Harbert displays a nice Keystone Lake largemouth bass taken during a recent outing.

The aquatic environment in which fish live is a dynamic, ever-changing one. Be it a lake, river, or reservoir, factors such as weather, water temperature, water clarity, available food supplies (and location of such), cover options, and a host of other complexities tie-in to the tactics we as anglers employ, and how effective those efforts are.

Nearby Keystone Lake in eastern Armstrong County is a good example. While a reservoir, its characteristics mimic that of a natural lake. It’s feeder waters are small, so the lake’s retention time is great. I once heard it takes about five years for water entering the headwaters from Plum Creek to make it to the earthen dam, about five miles downstream. I can’t comment on the accuracy of this statement, but there’s no doubt the lake’s depth and substantial size (by Pennsylvania standards) allow it to build up nutrients that help fuel its fishery.

From a cover standpoint, the lake features submerged weeds that grow out to depths of nearly 20 feet. Milfoil, coontail and various pondweeds (commonly called cabbage) are present in many areas, and collect both gamefish and panfish, particularly where they are found on structural elements like flats, humps and points.

Considering the lake’s food base, there are emerald shiners and rainbow smelt, species that tend to live in open water, feeding on various forms of plankton and other minuscule food sources. There are also young sunfish and perch, species likely to be found seeking food and shelter in weedbeds. Shallow rocky areas are home to crayfish. Aquatic insects are also present, and in their various life stages also likely add to the food chain. All this paint the picture of a multifaceted environment in which bass, walleyes, tiger muskies and panfish have a variety of options to meet their needs.

Weather is a factor that influences how gamefish like bass use these options, and though there are exceptions, in general, as weather fronts are moving in, bass are shallow and chasing, and during the backside of a front, expect to fish deeper and slower. A couple recent trips to Keystone illustrate this.

The day was clear when Stuart Harbert and I left the Atwood access around 7 a.m. Conditions would change during the day, with mid-afternoon and evening storms descending that would cause catastrophic flash flooding in the nearby area.

Harbert, from Houston, Texas, was in the region for business and had set aside a day to chase smallmouth bass with me on the Allegheny River. High, dirty water precluded that option. I hoped Keystone, which is home to quality-sized smallies, would help fill the void.

During the morning hours, we worked a variety of cover options, but all our action took place near weed edges, primarily from largemouth bass fooled by a slowly sinking, unweighted sinking stickbait. As cloud cover increased and the southwest breezes picked up, we began catching smallmouth bass along shallow, gravel/slate banks, ones exposed to the stiffening wind. At one point, we picked up a half-dozen brown bass on just about as many casts, fish that chased down a high energy suspending jerkbait. The action remained good until an approaching storm chased us from the lake.

A few days later — under significantly different conditions — my friend Dave Keith and I revisited Keystone for an afternoon/evening trip. The string of stormy days had given way to clearer, drier air, accompanied by a 10-20 mph wind. We arrived just as a bass tournament was finishing up, so it was likely many of the spots, particularly the shallower ones, had seen plenty of angler attention.

The weedbeds produced some bass, but the action was slow. Eventually we began working deeper water off the end of long point, where the tip dropped from 15 feet of water down into 25. Clouds of baitfish showed up on the sonar along this drop-off in the 20-foot range. Several quality-sized bass took a Texas-rigged finesse-style plastic worm, one fished pretty much vertically over the base of the point.

Working several similar areas, we experienced similar action on some. On one of them Dave lost a heavy fish — likely a big walleye — that straightened the light-wire hook on the swimming jig/ribbon leech combo he was using.

Keystone Lake is a challenging venue, one that tests your angling versatility. Being aware of its complexity, and how gamefish relate to changing conditions, increases the likelihood it will provide rewards.

Jeff Knapp is an outdoors columnist for the Butler Eagle