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Thread: Are You Fishing Too Deep?

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    Default Are You Fishing Too Deep?


    Thanks to Larry-Southern IN I went to the BnM web site and read the news storys there. The first one caught my attention not because of the pretty young lady ( well that too LOL) but because of the gist of the story. What the author failed to realize was that he at first was fishing way too deep. Why? Well his depth finder told him the fish were 10Ft away from the transducer. But he Misunderstood what his depth finder was telling him. He thought the fish were 10ft deep or 10ft below the surface. Actually he was dead wrong! Why was he wrong? Well 10ft away does not mean 10ft deep. This is a CRITICAL MISTAKE that I often have made. I forget how the depth finder works and if I had not gone back and read an 1976 article about how depth sounders work I would have missed this key point again. Hopefully when I am out on the water I will remember this key point. Time for another graphic here. Will be right back to finish this story and show you why he didn't catch fish right away. In the mean time here is the web site where the article is found. Read it first and then read the rest of my post after I come back and add to this initial post.

    http://www.bnmpoles.com/newsletter/011705/011705.html


    Try not to drool over his cute daughter ! LOL


    ok here is the image that I promised that shows what I am trying to get across here.

    Remember that the actual cone of sound does not quite look like my crude drawing. I will try to post a more accurate diagram of what the cone of sound should look like in 2 dimentions. Remember that the cone of sound influnence is actually 3 dimentional and varys with the amount of power output. You increase the senitivity on your depth sounder and the cone will increase in size. You decrease the sensitivity and the cone angle will decrease. All other things being equal.
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    Last edited by Moose1am; 01-18-2005 at 03:21 PM.
    Regards,

    Moose1am

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    Barnacle Bill's Avatar
    Barnacle Bill is offline Super Mod and 2014 Crappie.com Man of the Year * Crappie.com Supporter
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    I gotta disagree with that one. A fish 4 foot deep is going to be in the field of view for approx 1.3 ft. That is with a standard 20 degree transducer. There is no way it could measure 10 ft away even at the edge of the cone. Now with some of these new fangled super wide, multi-transducer setups, I could see where that might apply. I definately go along with the fast trolling this time of the year. I've been doing that for years and it does work.
    Fair Winds and Following Seas

    Bill H. PTC USN Ret
    Chesapeake, Va


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    OK I admit that I over did the dimensions but the principle still works. Would you catch the same fish if he were only 8ft deep and you fished 10ft deep? See my point now?

    Let me change the graphic and then maybe it will make sense

    Also you bring up another variable with transducers. Wide angle cones. There are some transducers that shoot sound waves out to 45 deg on either side of the boat. So in deeper water these wide angle tranducers are showing fish that are out to the side of the boat.


    Quote Originally Posted by IBNFSHN
    I gotta disagree with that one. A fish 4 foot deep is going to be in the field of view for approx 1.3 ft. That is with a standard 20 degree transducer. There is no way it could measure 10 ft away even at the edge of the cone. Now with some of these new fangled super wide, multi-transducer setups, I could see where that might apply. I definately go along with the fast trolling this time of the year. I've been doing that for years and it does work.
    Regards,

    Moose1am

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    It takes a transducer angle of 133 degrees for the math to work out. That would be one huge fish arch!
    Keith
    2008 NWR Bash Crappie Champion
    2010 NWR Bash Yellow Perch Champion
    2010 Buggs Bash Smallest Crappie Award

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    The fast trolling is what surprised me. I should know by now that life if full of surprises and variations. LOL

    I have very limited experience in winter fishing but I have had some. Last year I was able to find some suspended crappie out in the middle of a lake and actually caught them using slow vertical jigging. But that day it got up to 50 deg F and it was nice and sunny when I went fishing.

    I think that one thing we should remember that as the sun changes position and the winds pick up or lessen or even change direction that the fish respond quickly to these changes.

    In the KY Lake Crappie Study that was written about in the Feb Issue of In-Fishermen Magazine the author of the study described how one crappie traveled over 4miles in one 24 hour period. The other crappie that he tracked for 24 hours that one day didn't move hardly at all. So not only do we have the varabiles of the weather but we have fish with different attitudes and behaviours.

    I think the main point in the article was that he needed to fish shallower. Remember that by going faster the lures actually will rise up and be in shallower water. Maybe slow and shallow would work well too.

    He didn't tell us the water temps in the article and if they were rising or falling or did he?

    Quote Originally Posted by IBNFSHN
    I gotta disagree with that one. A fish 4 foot deep is going to be in the field of view for approx 1.3 ft. That is with a standard 20 degree transducer. There is no way it could measure 10 ft away even at the edge of the cone. Now with some of these new fangled super wide, multi-transducer setups, I could see where that might apply. I definately go along with the fast trolling this time of the year. I've been doing that for years and it does work.
    Regards,

    Moose1am

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    If you did the math with 4ft and 10ft then please recalculate with the new measurements. I can refine the numbers to make the cone angle 45 deg. if necessary. Also is a 20 deg cone angle the angle between the middle of the cone and the outer edge or from one edge to the other edge of the cone?

    Can you redo the math again. Use 8ft and 10ft this time and tell me the angle of the dangle. I hated Trig. Sin Cos Tan Rads Grads and Radians LOL


    Quote Originally Posted by PanMan_VA
    It takes a transducer angle of 133 degrees for the math to work out. That would be one huge fish arch!
    Regards,

    Moose1am

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    Finally someone got it. Thanks Tool. I hope it works. I know that I am going to try to remember this.

    Another thing that I take into consideration is how deep my tranducer sits in the water. My old depth sounder will not compensate for the two feet depth of my transducer which I moutned on the bottom of my trolling motor. So I have to do the math in my head. Fish on my depth sound that show up at 8ft deep are acually only 8ft away from my transducer because my transducer is already 2ft deep when it starts. So a fish's depth is hard to determine.

    Best thing to do is vary the depth a few feet on either side of what the depth finder says. Like bracketing the exposure setting on a camera.


    Quote Originally Posted by tool
    Early this winter I was on Wylie trolling during the day with pete up north above the buster boyd bridge and we weren't catching squat. I sped the trolling motor up from .3-.5mph to .8-1.2 mph on the gps and we caught several crappies and a good sized green carp on our 1/16 oz jigs. I think we were fishing them too deep because of our slower speeds. I can't wait to get out and give this method a try.
    Regards,

    Moose1am

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    Barnacle Bill's Avatar
    Barnacle Bill is offline Super Mod and 2014 Crappie.com Man of the Year * Crappie.com Supporter
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    Hey Moose, the cone angle is edge to edge. I forget all that math stuff. I used to have to do oblique rectification with aerial photography way back in my Navy days. That is one of those things that if you don't work just about daily with, you forget. And believe me, My forgetter works real good today. LOL

    I've read in several places that a rule of the thumb for 20 deg transducers is the area of coverage is about 1/3 the depth. So in 30 ft of water, you are seeing about 10 ft of the bottom. A lot of the newer sonars you can compensate for the depth of the transducer (in programming) so you get an accurate reading.

    Back to the fast trolling. We discovered that by accident many years ago. We were fishing one of the local rivers and not doing much. So we decided to try some place else and rather than taking in all 16 poles I just cranked up the trolling motor. Lo and behold, I went across the mouth of a creek and we caught fish. You get the idea. Anyway, at the time I figured they were just feeding shallow and I needed to adjust my bobbers. That didn't work. They wanted a fast moving, shallow bait. Since then, we vary our trolling speed until we find what they want that day, or rather that hour because it can change in a heartbeat. Like Tool, our speed may vary anywhere from .5 to 1.5 mph.
    Fair Winds and Following Seas

    Bill H. PTC USN Ret
    Chesapeake, Va


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    Quote Originally Posted by Moose1am
    If you did the math with 4ft and 10ft then please recalculate with the new measurements. I can refine the numbers to make the cone angle 45 deg. if necessary. Also is a 20 deg cone angle the angle between the middle of the cone and the outer edge or from one edge to the other edge of the cone?

    Can you redo the math again. Use 8ft and 10ft this time and tell me the angle of the dangle. I hated Trig. Sin Cos Tan Rads Grads and Radians LOL
    74 degrees with the revised dimensions. The angle is measured for the entire cone, but calculations use half the cone angle in order to get a right triangle. From there, its a simple cosine function for depth or a sine function for distance from the transducer. I've seen arches like these when using my 50 KHz transducer.

    Your other point about trolling is right on.
    Keith
    2008 NWR Bash Crappie Champion
    2010 NWR Bash Yellow Perch Champion
    2010 Buggs Bash Smallest Crappie Award

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    Let's not forget that crappie feed upward. My only flasher is the vex in winter so speed trolling is kind of limited to about 5 inches at most. Point is a local fave lake the guys see the fish sitting on bottom in 7-11 feet of water. Rookies drop the jigs right down there amongst them and catch a few. Old pros like myself fish 2-5 feet down and let the hungery ones come up and nail it. Now on open water, I rarely have success in the depths people like to post and write articles about but I know I am doing it wrong with the wrong equipment and lures so limiting out doesn't hurt that bad.

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