I just went on a guided trip with a very proven angler. It was more of a coach than a guide. One thing he told me was the shape of the arch on 2-d sonar could tell what species of fish it was. The perfect arch was usually carp, drum, crappie, or bluegill. They are a square shaped fish. Bass didn't give off a perfect arch instead it was more like a comma. Now this sounded a little odd to me but since he was pro at one time I couldn't argue. Thoughts anyone?

A "comma" shape is due to a tilted transducer, a fish to the left or right of the sonar pulse or a moving fish when within the sonar coverage. Species is irrelevant.

Sort of common knowledge with sonar users.

An arch is created by time and distance within the sonar pulse. Time from when it is in the coverage until it is not, and distance from the transducer (peak of the arch is the closest).

Just do a web search for " fish arches "

This.

Those arches are fish!!!!???


Damn...I guess my graphs ARE working. Maybe it's just me after all.

Was this at Fork? I went with someone who does instructional fishing there and he tried telling me the same thing.

Oldie but a goodie..

http://texasfishingforum.com/forums/ubbthreads.php/topics/7586487/all/Post_your_graph_pictures_of_ba

Yes it was Bobby. I'm sure it was the same guy. Caught some really good fish though.

For the sonar to produce a perfect arch, the boat and fish needs to be almost still and the fish needs to be in the middle of the beam. If it is elongated it is off to one side or moving. Guessing species comes with experience on how thick the arches and a lot of times if there are schools, how they align in the water colum. A lot of varibles.

To get a perfect arch you gonna need movement. If the fish and boat are sitting still you are just gonna get a continues long line cause the transducer keeps pinging the same object

This^^ if your idling over fish they will look different than when your on your trolling motor sitting on top of them.

that's why I said almost still