You have a really good start. I would get into fish like this again and do as i suggested above. pause the screen and adjust sensitivity and contrast until the fish pop off the screen.

Looks to me you are running Sensitivity a little too high but not too bad. Might cut down a little on your range. Looks well over 4 or 5 x the depth you are running.

The shots produced great shadows. The Shadows are almost as important as the fish returns themselves. Gives you an idea where the fish are in the water column without running over them.

Not sure how many color pallets you have tried. Try inverse. Black on white.... can't get more contrast than that.