See if you can find a good map of the area that shows depth and contour. I'm with Scat on this one. This time of year, these fish are looking for deeper water. Although they may not be down to the depths, this is what they are suspending over. You might find after looking at a map that you have been fishing some pretty shallow areas. If bank fishing is all you have, concentrate your efforts on contour lines that are close to the bank and reachable by casting from shore.

Vary your depth with a slip bobber until you find the depth they are after. Although harder to find than shallow areas and bays, when you find these deeper spots that you can reach from shore, you will find the fish!