Most of these are in areas where the winter water temperatures are at optimum levels for the target species. For example, in parts of California where reservoirs offer a black bass and panfish fishery save for deep trolling during the warm months, you can catch striped bass, smallmouths and trout right up on top. Such also holds in the south where striped bass can chase bait in reservoirs. If it's colder than optimum in the lake or reservoir check temperatures of inlet streams. Stream inlets are usually good, and warmer streams, like warmer underground springs can key action.
Temperatures vary across a lake too.
Sunny flats with dark bottoms can heat up. So can the water right next to light colored rocks that reflect sunlight. Open meadow banks that get lots of sun are usually somewhat warmer than steep, shaded banks. Use of simple thermometer, like an eye on bird action or fish swirling improves results. As a rule baits work better than lures as waters cool and fish slow down.