Re: Found "em - can't catch 'em
The only problem with fishfinders is that they fail to tell you two important things: A) what kind of fish they are and B) whether or not they are hungry . I usually move back to smaller water about this time of year. In small ponds and lakes, a single sunny day can create enough difference in the shallower areas to turn the fishing on.
Cold water slows a fishes metabolism (they are cold-blooded after all) so they feed less often and much less aggressively.
Also, it may be that they were biting, only between the depth and the sinking line you weren't able to detect the strikes. It's a common problem with warmwater fish in cold water. They start biting real light and just taste the fly instead of inhaling it like they do when warmer water temps make them more active feeders.
Just a few thoughts
If it swims and eats, it'll eat a fly.