This is something that can be a big-time clue when you’re trying to figure out the prespawn period. I’m always going check their bellies before I release them. If they’re skinny and look like a windsock, I assume that fish has already spawned which means I might be behind the pattern. Instead of catching fresh prespawners, I might be better off to go search some of my favorite post-spawn spots.
If your fish have big ol’ pot bellies, however, you’re in business and can expect your pattern to remain consistent for a few weeks. To figure out exactly how long the prespawn deal will last is impossible, but you can take an even closer look at their bellies to get an additional clue. Right when the bass begin moving up into prespawn staging areas, they’ll often put their bellies right on the bottom of a red clay bank. These clay banks conduct and hold heat better and longer than most other bottom compositions, which makes them an excellent place for a bass to warm their egg sacs. So before you release that bass, make sure to look at its belly for any discoloration. You’ll literally see red clay stains on their stomachs which means they just moved up and are beginning to get romance on their minds.