You can't Identify fish with a fishfinder....

[Cane Pole]

Fishfinders will not identify fish...Period...The meaty part of the fish is 98 % water with little or no echo from the sonar ping. I have said this before, and now I repeat it. what the finder echos back ( with respect to fishes) is the air bladder of the fish. What you can do is learn the habits of the fish and assume the species. That is all.

here is a good link on this stuff....it is a good read folks... It even explains some of the stuff Moose has chattered about.

http://www.vexilar.com/help/tips/tip011.html

[DENNIS BOWERS]

I Agree With You Canepole-i Just Make An Educated Guess Going On Location,time Of Year,structure ,ect!!i Have Found By Doing This Though That A Good Percentage Of The Time Their Crappie. Thanks For The Link-i"m Gonna Read It!!good Fishin To Ya!!!dennis

[Ranger690]

I don't subscrib to the air bladder thing. All the leaves and sticks I mark don't have air bladders. And trash in an eddy looks just like a school of gizzard shad.

To each his own.

Dayton

[reelcrappie]

When I first started fishing back in the stone age I never dreamed that anything like the sonar units we have now were possible. My first fishfinder in the early 60's was a raytheon flasher and cost about 300 bucks. Now for about half that you can get a sonar unit that would make that old flasher look bad. I'm just tickled to be able to see the depth and bottom contours. I still marvel!

[Moose1am]

Here is another web site that gives links to using SONAR

http://www.battlefront.com/discuss/u...;f=41;t=000178

These sites should explain how the Navy uses Sonar to find enemey submarines. After all this is where we got the knowledge to develop the present day depth sounders that we use for fishing in inland waters and on the worlds oceans.

And if you really get into SONAR you can play Dangerous Waters new Naval Simulation Game. LOL

Lots of information to learn here guys. More than enough to keep you busy in the winter months .. unless you live down south like Jerry where the water temps never dip too low. Every time I ask him what the water temps are he says around 50 deg LOL Must be nice to have that kind of water almost year round.

Sonar is usefull for seeing land under your boat. It may show some things suspended in the water.

Cane Pole I do have one correction. Sound will not travel though air like it does though water. I am not sure but I think that the sound waves that bounch off a fish are bouncing off it's flesh more than the air inside the swim bladder. But I could be wrong. I do know that if you have air between your transducer and the water that it will not work. When you epoxy the transducer to the bottom of a single hull thickess bass boat you can't get any air bubbles in the epoxy glue or the tranduer will not work well.

Again sound waves travel four time faster in water than in air. I suspect that pertains to all wavelenghts but I am not sure. But at 200 Khertz and 50K hertz those wave lenghts that I read the most about on our depth sounder the air will prevent the sound from getting into the water with suffecient energy to work right.

A good tranducer setup will have the transducer in good contact with the water and in a water flow that is absent of air bubbles. Air bubbles cause the depth sounder display to go bonkers.

Fishfinders will not identify fish...Period...The meaty part of the fish is 98 % water with little or no echo from the sonar ping. I have said this before, and now I repeat it. what the finder echos back ( with respect to fishes) is the air bladder of the fish. What you can do is learn the habits of the fish and assume the species. That is all.

here is a good link on this stuff....it is a good read folks... It even explains some of the stuff Moose has chattered about.

http://www.vexilar.com/help/tips/tip011.html

[Moose1am]

Some of those diagrams were in my old fishing facts magazine 1976. The picure showing how we think the fish are vs how the fish really are was definately the same picture in my FF 1976 magazine. I recognize that picture anywhere. Seems like a lot of people are using that these days. It's a great diagram and one that I used a while back to talk about depth sounders and how they work. It's the one that Big J went off on when I posted it in 6 sections. LOL I can still remember the chat conversation that night when he first saw my 6 page post LOL I get a big kick out of that nowdays. LOL

Hey Big J. I read that you were working. Not sure if you are back at the tire company or doing more work with the business you have. Hope all is well mate.

Fishfinders will not identify fish...Period...The meaty part of the fish is 98 % water with little or no echo from the sonar ping. I have said this before, and now I repeat it. what the finder echos back ( with respect to fishes) is the air bladder of the fish. What you can do is learn the habits of the fish and assume the species. That is all.

here is a good link on this stuff....it is a good read folks... It even explains some of the stuff Moose has chattered about.

http://www.vexilar.com/help/tips/tip011.html

[Moose1am]

I'll re-educate Cane Pole on the finer points of Sonar this April when I go fishing with him. LOL

Remember that you can see a thermocline on a depth sounder and there is no air there. Not any more than what is already dissolved in the water in PPM quantities. What you see at the thermocline is water of different temperatures and thus different densities.

I posted in another thread a link to a lot more links on how Sonar works in the ocean. There you have to look at the temperature profile of the ocean from top to bottom and the salenitiy levels and see how they effect the way sound waves travel though the water. This is a pretty complicated subject.

I get lost in the logarithmic mathmatics on the decibles. LOL Sound pressure measurements were hard for me to understand for some reason. Log math and that stuff I had to take in summer school. It was one of those 8 week long self study courses that I took while working at a fast food joint a nights to eary spending money. Class during the day for 8 weeks and working nights till 7 am. I lived for the weekends between my jurnior and senior year of HS. I can remember driving home at 7 am trying to stay away and not run off the road. Have you ever drank cold coffee and slapped yourself in the face to make it back home?

I don't subscrib to the air bladder thing. All the leaves and sticks I mark don't have air bladders. And trash in an eddy looks just like a school of gizzard shad.

To each his own.

Dayton

[Cane Pole]

Sonar works off a reflected sound wave. Period. The transmitter turns on for a short burst of time (ping), then turns off. The receiver then turns on waiting for the returned signal. The time it takes to receive that returned signal is the distance to the object. The strength of the signal that is returned is the size/shape/density of the object. This is how it works. The more dense the object the sound wave strikes, the stronger the returned signal. The rest is mathmatical algorithms received and massaged by a microprocessor to determine what is what.

This is my story and I am sticking to it.