The Transition From Spring To Summer

For suspended crappies, water temperature can be a better guide to good fishing. Especially on large lakes, surface temperature can vary by 4 or 5 degrees from one area to the next. The warmest water tends to hold the most plankton (though that’s not always true), and the edges where colder masses of water meet warmer masses can create a plow effect, concentrating plankton and baitfish along the edge. In open water, several acres of the surface might read 74°F, while several adjacent acres might read 69°F. Using a surface-temperature gauge, look for that transition zone where the temperature begins to change and scout it for plankton veils, surface activity, and schools of baitfish.

When the wind changes direction often over a three- or four-day period, patterns can dissipate. Some crappies remain in open water but scatter to the point where it becomes difficult to locate fishable concentrations. Crappies may begin to concentrate on deeper structural items or on existing cover on those structural items, suggesting a switch to a different pattern.

Humps, Brushpiles, Rockpiles and Reefs

One of the most overlooked summer patterns for crappies in natural lakes involves deep cover, and this pattern has a lot to do with thermoclines. Natural lakes tend to set up thermoclines somewhere between early and mid-summer, depending on weather patterns. The thermocline is a transition zone between an upper layer of warmer, highly oxygenated water (epilimnion) and a lower layer of cooler, less-oxygenated water (hypolimnion). Thermoclines can establish as shallow as 8 feet down or can be pushed as deep as 100 feet or more (especially in very large bodies of water like the Great Lakes); but a more typical range for thermoclines is between 20 and 40 feet.

The thermocline is a band of water that typically extends 6 to 10 feet from top to bottom. Within that band, temperatures decline quickly from top to bottom. The epilimnion may read 74°F on the surface and the temperature may only drop 10°F, to 64°F, at 30 feet. But within the thermocline, temperatures can drop another 10°F in a span of only 10 feet—1°F per foot or, in some cases, even faster. Where thermoclines establish in a lake has to do with overall depth, natural currents, wind-driven currents, atmospheric pressure, mineral content of the water, and a host of other factors.

Thermoclines can be located by a variety of means. The most popular method for anglers involves the use of sonar. With the gain turned up on a good depth-finder, the water-density change within a thermocline can be detected as a band of gray or indeterminate color, or (on color monitors) as a distinct band of light green or blue well above the bottom reading in deep water. The thermocline can be pushed deeper on the windward side of a lake, and can rise toward the surface of the lee side of a lake during periods of extended and consistent wind patterns.