Small Fish

Small Fish Identifying fish size is difficult with sonar. Since sonar determines size as echo strength and displays echo strength as different colors and how thick the fish arch is. Echo strength is different from targets at 5 feet or 20 feet from the transducer because sound get weaker as it travels through water. This is why auto sensitivity turns the sensitivity higher in deeper water. I have some examples of perch on this tutorial. http://www.hightechfishing.com/sizeandspecies.htm
The first screen shot is a lake with suspended small fish about 5 feet even if the water depth was 10 or 30 feet.
This screen shot shows the fish in shallow water.
This video is poor quality but shows the small fish suspended at 5 feet. The lake has limited sunlight penetration and the day was cloudy. The small fish show up as dark spots on white background in the upper part of the screen. I have tried and I can’t identify the species from my underwater video. This small fish video is part of a tutorial on understanding sonar using underwater video to match the sonar display.

The last screen shot is from a different lake and shows fish (walleyes 1-4 lbs) and a sinker and a 5 inch creek chub (minnow). The sinker is 2 feet from the minnow. As I lift the sinker, the minnow follows and the same happens as I drop the sinker. The walleyes also followed the minnow up and down.

But the important point is the display size of a 5 inch minnow vs. the walleyes in 24 feet of water. On this screen shot compare the amount of yellow in the minnow and the thickness of the arch to the walleyes.