The size of the arches is dependent upon where in the sonar cone the fish is located, not how deep they are. If your boat is not moving and you see a half arch near the bottom (pic #1), that would indicate to me that the fish is on the edge of the cone angle. Full arches indicate fish, period. They do not define species. Dots & dashes and/or "globs" usually indicate bait. The fish between 10 & 20 feet on the left might just be crappie. The arches around 8' on the right picture are definitely fish. But again, no telling the species. And the clouded marks above those fish appear to be bait to me. JMO!