Fish On Depth Finder

[Rippinlips14]

I struggle on what fish look like on a depth finder i have an 8 level grey scale depth finder and always struggle to see what fish look like can anyone help me by showing examples of some fish on depth finder screen. And will they always be an arch or will only their air bladder show up instead of their air bladder and two lines coming off the front and back?

[Wayne P.]

A 2D display can only record the echos from "stuff" in the water.

A fish has an air bladder. Air bubbles reflect sonar pulses. Echos are returned from suspended matter also, like leaves, trees, plankton and even temperature changes.

 

An arch is recorded because a subject is first detected at the outer edge of its coverage, farthest from the transducer (beginning of the arch shape). As the subject passes through the sonar coverage it gets closer to the transducer. At the closest point it is directly under the transducer (peak of the arch). As the subject gets farther away, the other end of the arch is recorded until it is no longer detected.

 

Bottom line is it has nothing to do with a fish's shape or even if it is a fish. It is entirely a result if time and distance of a subject within the sonar coverage.

 

If you know your waters, then you would know if an arch is a representation of a fish or some other subject.

 

There are several example of fish arches posted in the Screenshots topic above.,

[Wayne P.]

Additionally if you want to see a cartoon example of how a fish arch is recorded, go to the Lowrance website and locate the Sonar Tutorial. Towards the end is the arch cartoon.

 

Additionally since time and distance is what forms the arch, the boat speed, fish speed, and/or unit screen scroll speed affects how and what size it is recorded.