Not necessarily as that would be a user preference. Fish showing as arcs takes several things to have happen.
- The fish need to pass through the center of the transducer beam (or at least close to the center)
- The sonar beam has to be wide enough so that the depth scale used will be able to show the difference in distance to the fish as it starts into the sonar beam, as it passes through the center of the sonar beam (closest point to the transducer) and than as it gets farther away from the transducer as it exits the sonar beam.
- The depth scale used and the vertical pixel count of the display needs to be such that it can show these differences in distance between the fish and the transducer.
- The display update speed needs to be set so that fish will have the chance to show as an arc instead of a flat line or jumbled up group of pixels. By setting up the correct display update speed you are really setting up the correct relationship of the speed between the fish (which may be moving too) and the transducer (boat).
- The transducer needs to be as close to being parallel with the surface of the water as you can get it or full arcs may not be able to be formed (his looks a little low in the back end for me).