Circling back over the sunken structure, our depth finder showed a small school of fish-shaped blips again.

Joe Wilkinson Outdoors

We had been marking a few fish, trolling back and forth over a half acre on Lake Macbride. This particular spot, though, about 11 feet deep, with a pallet "cube" of habitat, consistently showed fish hanging about 5 or 6 feet deep.

And, on cue, neighbor Larry's pole bent over and he lifted another 9-inch crappie over the side. I checked mine. Same jig-and-a-minnow, same depth. My pole was untouched, though, just a few feet away.

I had been using bigger minnows, seined the night before. Eventually, after switching to Larry's smaller, bait shop minnows, I did interest a couple crappies. The two I boated pushed us over a dozen; not bad for the two-hour foray. And not bad for a midsummer fishing trip, when the bite often slows down.

But it doesn't have to.

"Look around, see what other people are catching," suggests Don Bonneau, fisheries research supervisor for the Department of Natural Resources. "Check our 'DNR Hawkeye Hotspots' report. Ask at the local bait shop. Talk with other anglers. Not every lake provides good fishing all the time."

On one hand, fish are more active in hot weather. Their metabolism is high. They are eating more. On the other hand, there is plenty of natural food for them, with an explosion of insect hatches and young of the year fish. With fish surrounded by more natural foods, minnows, nightcrawlers, crawdads and other live bait usually work well.

Depth for fishing depends on what species you are chasing.

"Bluegills spawn several times during the summer, so you'll want to stay shallow, looking for them," Bonneau said. "Largemouth bass and channel catfish can be located close to shore, too. Bass will be near cover, stumps, wood structure. They and bluegills will also use vegetation. It's overhead cover and shade for them. It also holds a variety of zooplankton and insects which, in turn, attract baitfish."

In deeper water, crappies will often suspend about halfway down. They and bluegills are schooling fish. Catch one and you'll find more. That's what we were finding on our two-hour crappie run. Each time the boat trolled out of the hot zone, the depth-finder sightings would tail off and the bites would stop. As we floated back across, the poles would bend again.

Late-summer anglers must also factor in the thermoclines present in lakes. With little water movement, many lakes stratify. Colder water on the bottom of the lake holds virtually no oxygen. Therefore, fish concentrate in the top layer. A good rule of thumb is that the thermocline will develop about halfway to the deepest depth; a lake that is 40 feet deep will stratify at about 20 feet, for instance.

In addition to changing your tactics, you might also consider a change of time.

"Some of our best fishing is after dark," Bonneau said. "A lot of people don't realize that; and that lights are legal for fishing. Early in the morning, late in the evening, after dark are great times for crappies and white bass."

Iowa's four flood control reservoirs (Coralville, Red Rock, Rathbun and Saylorville) offer good populations of white bass as an attractive summer option. Other impoundments hold catchable numbers of them - stripers as they are called in east central Iowa. A good way to target them? Look to the sky.

"Watch the gulls," Bonneau said. "They are a sure giveaway that shad or other baitfish are getting riled up; likely chased by schools of white bass."

Telltale splashes on the water surface are good signs, too, as the shad leap from the water trying to escape.

Morning, evening? Deep or shallow? Panfish or catfish? Bonneau offers a simple tip.

"Fish when you get the chance."