When bass pro Shane Lineberger idles over deep water during winter, he wants to see multiple schools of baitfish on his fish finder before he stops to make a cast. He knows the spot will be even better when he sees “spaghetti.”

On a fish finder, predator fish usually show as arches, and baitfish schools as smudges. Lineberger said arches inside or above a baitfish school are most often smaller fish such as white perch or hybrid bass. 

“Bigger fish, especially bigger bass, are going to be under the bait,” he said. 

On days when the sky is bright and clear, angler Glenn Grindstaff said the arches will be close to the bottom.

“On a slow day, especially, they can be so close to the bottom that you can’t distinguish them, especially on a sloping bank,” he said. “Sometimes, you just have to fish them.” 

But on good days, when bass are active, arches become lines that stack up between the baitfish and bottom. The lines, which remind Lineberger of a plate of spaghetti, represent bass that are swimming through the depth finder’s transducer cone on their way to eat baitfish. Arches appear when bass are not moving.

Seeing smudges, lines and arches takes more than just firing up your fish finder. Spend time reading the instructions and understanding its manual adjustments. Tweaking the sensitivity, for example, brings more into focus. Grindstaff sets it so traces of the sinker, swivel and minnow show on the screen. Color units help, too. Lineberger runs his Lowrance units on color palette 13, which shows the bottom as brown and harder spots as greens and reds.

But sometimes, you still need to go old school. Lineberger watches for birds, even on thew coldest days. They might not be crashing baitfish schools on the surface, but they’ll hang around to pick up expired shad that float to the surface from schools in deep water.