11/2014 Crappie arches at different speeds and with different sonar models On November 10, 2014

Crappie Fish Arches and Boat Speed
Slow boat speeds create long fish arches since the fish is under the boat longer.
I have some nice examples of using different boat speeds and different manufacturer’s sonar going over the same school of (10-11 ½ inch) suspended crappies to show the difference.
The first image is using a Humminbird 1199 Clear Mode with 200 kHz frequency at 5.3 mph.

This image is from a Lowrance 200 kHz frequency at about the same speed.

Notice the Lowrance has longer tails on the arches, this because Lowrance’s 200 kHz cone is a little wider and the “tail” of the arch is the fish on the edge of the cone. The transducers for both are the 200/83 models. If you used a 200/50 Lowrance transducer you would see shorter “tails” since that transducer has a narrower cone for the 200 kHz.
You can also make longer fish arch “tails” by using a lower frequency which usually gives a wider cone.
This is using the medium chirp with the TM150 transducer and the SonarHub. The cone is wider so you “see” fish on the edge of the cone and get longer tails. This image is not the school of crappies.

This image is using a Lowrance 200 kHz frequency while moving slowly over the school of crappies. Notice the fish arch flattens out.

This image is from a Raymarine a9 using the 200 kHz frequency at a speed of 2.3 mph which is in between the above images. The fish arches are shorter than not moving and longer than the Humminbird at 5.3 mph.

This image is walleyes using Humminbird 83 kHz on the left panel and 200 kHz on the right.
This shows why I prefer 200 kHz for my shallow water fishing. The 83 kHz has a wide cone which is putting more information on the screen than the 200 kHz so you lose the target separation.

The last image shows why I prefer down imaging side by side with my 2D sonar. The target separation is much better with down imaging. You can actually count the fish because the cone is narrow and therefore doesn’t display “tails”.

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