Springtime slabs milling all over the place. Right here. Yesterday afternoon. But not any more. Happens to anybody who fishes crappies long enough, but where did they go? The answer is on the screen of the nearest depthfinder. Not the depth or the structure or the absence of fish showing on the screen, but the temperature readout.

Warmwater fish, like crappies and bluegills, tend to be most sensitive to temperature changes at the cold end of the spectrum. In spring, when water temperatures range from 40°F to about 60°F, crappies are more likely to relocate after a 2°F drop in temperature than they are in the balmy 80°F waters of midsummer.

The water in lakes, rivers, and reservoirs cools almost every night in early spring. The overall effect is a gain in temperature as days continue to grow longer than nights, but every night the water chills and radiates away some of the heat it gained during the day. Severe cold fronts can cause water temperatures to drop during the day. Snow, cold rain, and heavy cloud cover hold the temperature steady or allow it to slide downward, too. But these are all examples of overall cooling. In these scenarios, the water temperature drops everywhere in all local bodies of water (except in the presence of a thermal discharge, warm spring, or inflow that’s warmer than the lake).

Crappies don’t like any of that. In every case of overall cooling, they tend to shut off or at least become neutral during early spring. Before the dogwoods bloom, the best times to pursue crappies tend to be afternoons after the sun warms the water, during stable weather on sunny days. It’s sometimes possible to finesse a bunch of crappies early in the morning or after a spate of poor weather, but it’s not likely to produce lifelong memories unless somebody falls out of the boat.

But water can cool in other ways. Some of the finest crappie spots in early spring are semi-enclosed or entirely enclosed, with only a channel leading in. River backwaters, small connected basins, and partially enclosed bays are the most stable environments crappies can find early in the year. If such habitats are not available, crappies may use channels or boat canals that connect marinas or housing developments to the main body of water. Crappies find nooks, crannies, and cuts along the lakeshore, or anything they can find that reduces the effect of the wind. The fewer directions the wind can take to reach them, the better, because wind can cool off an area even when the lake is warming overall during a sunny day.

Finding enclosed or semi-enclosed areas can be less than half the battle. Some river backwaters are vast and convoluted. Some connected basins and semi-enclosed bays are huge. Where to look now?

Whether crappies must endure the vagaries of large, open bays or enjoy the cozy comfort of a small isolated backwater is not the point. The point is, crappies are temperature-sensitive, more so right now than later in the season. On a warm, sunny day, crappies are biting somewhere. But you say the crappies were here yesterday? No bites today? Winston Churchill said, “If you are going through hell, keep going.” Don’t anchor. Don’t stop. Keep one foot on the trolling motor, one eye on the temperature gauge, and keep going until you find the warmest water around.

It’s possible to predict where that warm water is, to some extent. Even in backwaters and semi-enclosed bays—and even in well-protected canals—wind can affect localized water temperature. On a sunny day, the surface water of the lake or bay warms fastest. The warmest areas tend to be where the wind is blowing directly into shore, because warm surface waters are carried along by wind-driven currents. Where wind strikes the shore at an angle, the water tends to be cooler than where the wind hits the shore dead on. This can be an important distinction in spring, when a temperature differential of 1°F can mean the difference between a hot bite and a tepid one.