Sourbait is cutbait turned rotten, rancid, and ripe. Winter-killed fish don’t decompose in the cold water, but when temperatures begin to rise in spring, the gases inside these fish expand and the fish float to the surface. These floaters are driven by wind and current to predictable places—coves on the windward side of a lake, cuts on a reservoir creek arm, and large eddies in rivers. Catfish concentrate in these areas, too, gorging on these springtime delicacies.

Eventually, the abundance of sours declines and with it the bait’s effectiveness. Still, some baitfish are always dying, and during summer they quickly decompose, offering a somewhat constant although inconsistent source of sourbait. During summer, carp, in particular, tends to fish more effectively as sourbait than as fresh cutbait. It’s just tough enough to hold together and be a presentable bait, even during the warmest weather.

Doug Stange’s recipe for preparing sours: Start with a tough-skinned fish like carp. Other fish work, but some—like sour shad and shiners—too easily disintegrate when they hit the water. Such baitfish can be fished in nylon netting, but it’s a messy process. Meanwhile, scale and fillet the carp (or try sheepshead, mooneye, goldeye) and cut the fillets into 1 x 2- or 3-inch pieces about half an inch thick.

Pack the pieces into a glass jar, leaving an inch open at the top. Add a few teaspoons of water, or any other liquid you want to experiment with, to accelerate fermentation. Screw on the lid loosely—not too tight or the expanding gasses may cause the jar to explode. Bury the jar in 6 inches of soil that receives some sunlight for most of the day. Direct sunlight tends to break down fish too quickly, although experiment if you need the bait in short order. It’s best to let the bait fester for almost a week.

To use sourbait, hook it once through with the hook point exposed. The bait is just as effective rigged below a float as on a sliprig lying on bottom.