Pre-Spawn is my favorite seasonal period because it is the time when a catch of a lifetime can occur. Following the cold water period of late winter, pre-spawn begins when the water temperate approaches 55 degrees down to the depth of light. The female bass leave their deep sanctuaries and stage near structure breaks, that holds baitfish and clay or rocky soil where crawdads are coming out of hibernation, located close to the spawning flats. Wood cover like trees or brush on deep break lines is ideal if that type of cover is available.
The big bass are hungry and feeding to get ready for the spawn. These bass are usually in small groups or 5 to 15 fish and stay in the staging area for a few weeks or until the water warms to 58 to 60 degrees, then begin to cruise the spawning flats. Depending on the depth of light the big bass will stay a few feet above good light pentration and are establishing the territory they plan to spawn in.
The primary prey source for these big bass are emerging crawdads and baitfish. The presentations that trigger these bass are reaction baits that look like the prey fish or jigs and creature baits that mimic crawdads. Swim baits, spinner baits, crank baits, plastic worms and jigs. The emerging crawdads are green/brown in color, the baitfish will be predominately light color due to the colder water and your lures should be in those hues. It is a little early for salamanders or waterdogs to be a food source factor, however big bass will eat them if available and kill them on sight during the spawn. Bluegill and crappie are also a good baitfish during this time. Eels are a cold water food source and the darker color plastic worms and jig trailers work well.
On larger reservoirs the deeper water zones tend to warm later than the protected flats near deep water points or channels. Therefore you can follow the pre-spawn from the north west wind protected areas to the more wind prone areas and extend the pre-spawn period without targeting spawner's.
Smallmouth and spots tend to spawn at 58 to 62 degrees, where largemouth tend to spawn at 62 to 65 degrees. The bigger bass may spawn deeper down to 15 feet if the water clarity is very good or 6 to 2 feet in off color water. The smaller bass tend to be up in 1 to 3 feet. Clay with gravel/sand near wood / brush or tulle's is preferred for largemouth and rock/gravel for spots and smallmouth.