Guess Dr Sonar is right. The only way to know what are fish are on your graph is to catch them or view them on one of those underwater cameras that goes way down with a caveat that some species behave differently. Google him if you want to learn about how to read a graph. He sets up a sonar and underwater camera side by side to show what things look like on the graph. I would guess he knows way more about how to read a graph than anybody at any sonar company. It is not real easy to"really" read a graph in my opinion and takes a whole lot of time on the water to really get an idea of what you are looking at. The guy is a scientist, I think an retired MD by profession. Might be something to do this winter. The dvd I have put a friend of mine to sleep in about ten minutes. You know who you are. Dr Sonar will talk on the phone and recommend a dvd if you call. Here's the link: http://doctorsonar.com/
I was just about to tell you one of the things I learned on the dvd, but on second thought better not. It would be a zoo out there if everybody did it!
Last year I was fishing off low gap in 30-40 feet of water. A guide tole me to come over to where he was about 100' (maybe more) away. He said those are catfish you are looking at. I was like, wow, how does he know that. I thought I was on a fair number of smallish stripers.
Another funny one:
A friend was fishing near the mouth of a cove at Bugwoods. A guide was about 100' away and limited out. My friend asked the guide why he caught fish and he did not as they were doing about the same thing. The guide replied, "because the fish are over there". He didn't ask any more questions.
Another story.
I was down lining in the mouth of Guffy. I had a lowrance x70a and it was really old and loosing more and more rows of pixels. I new it was on its way out. It was probably the third one I had on repair returns not to mention all of the transducers I has swamped out. He yelled over and said, " is that an x70a"? I said' "yes". He said, "that's the best graph I ever owned". I didn't want to hear that given the shape mine way in and they had long since been replacing repair jobs with newer models. That ended up in about a two to three year sonar night mare with different units, returned and replaced.
Back to Dr Sonar. Do you know what the Dead Zone is? Well I didn't until watched one of his dvd's. Depending on the slope of the bottom you may not be able to see say for example the bottom 20' of water and there might be a whole school of fish in that water. No way it's physically possible to see those fish. When you are searching for fish on a steeply sloping bank an narrow cone is better than a wide cone. The x70a had a 12 degree cone. Good for targeting deep fish by sloping banks. My current graph has a 20 & maybe a 30 degree cone. Shoot, I can see my bait 15' deep on the inside planner board. That's good for just riding around with boards because you know there are fish in the area. For targeting fish near drop-offs like the smaller cone angle will enable you to see the fish near the bottom. You can' see them when they are actually on the bottom according to the doctor.
I'm getting dizzy smoking a cigar thinking abut all this. I just hope my current graph lasts a long time or I'll have to learn a new one all over again.