When you get on them you can smell them in the air. Get to a spot that smells real fishy and start looking for nests. Many fish finders even with side scan won't work well enough to show them in very shallow water.
Humminbird Side Imaging will show them as long as the transducer is not buried in the bottom.
Humminbird Helix 12 SI, 1198c SI, 1198c SI, ONIX 10 SI NT, 360, RC-1