Fish Size Question on SI

I took this first shot on Dale Hollow Lake while on vacation. Right after this snapshot I placed my cursor on the school and went over and caught a dozen nice ~10" bluegills and one 6# catfish.
Attachment 252207

This second screenshot is from a lake near my home in Ohio. From this location I caught around ten ~ 10-12" crappies.
Attachment 252208

What I can't figure out is that in the Bluegill image the fish "dots" appear much bigger to me than in the Crappie image but the actual size of the fish is very close. Why would that be? The only thing I can figure is that in the Bluegill image the school is so tightly packed that each "dot" actually is representing several fish...? Any ideas?

BTW I really like the Sonar Quiz Thread. Have really learned a lot from that thread!

Also, I noticed looking at these two images together that both have the same vertical line on the left hand side of the image (very shallow in water column). Any ideas what might be causing that? The only thing I can figure there is that I have a ladder mounted on the left side and maybe it is causing some turbulence???

Water depth 1st image is 9.9ft ...
Water depth 2nd image is 16.7ft ...
Noted fish echoes are at about the same place in both images ...

= The fish in the 1st image are 6.8ft closer to the xducer than the fish in the 2nd image ... making the echoes larger ...

Rickie

Quote:

---

Originally Posted by kfi

Also, I noticed looking at these two images together that both have the same vertical line on the left hand side of the image (very shallow in water column). Any ideas what might be causing that? The only thing I can figure there is that I have a ladder mounted on the left side and maybe it is causing some turbulence???

---

The HB SI beam reaches from the water surface to past vertical under the boat ...

Your left SI beam is echoing off the ladder itself ...
http://i477.photobucket.com/albums/r...pskwnh5zhd.png

Rickie