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Stacked marks, what is it?


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I always assumed that to be a school of fish and the reason they stack up like that is because the tranducer is picking up multiple fish @ the same depths within the "signal cone".I know when I start marking that it usually isnt long til fish on. I would like to know the real proven reason for this also, good question.

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If you are fishing near another boat at times you may see interferences from the other boats similar to what you are showing due to frequency interference from thier graph or any other equipment that is sending a pulse thru a transducer.

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Thanks for the replies guys.

Graph info: Hummingbird 798. I have the sensitivity and most of the settings turned way up(most on max) when out on the big lake. Helps me to see the "arches". Freq is 200/83 KHZ(when in dual beam mode). Its mounted on the back of my 16.5 aluminum boat.

I don't get these marks like that all the time. Every once in a while, and only on the big lake as I can recall. When I'm on MAC or muskie fishing a smaller inland lake my settings are TOTALLY different and I don't recall seeing this phenomenon.

I kinda thought it might be a rigger cable as the front edge of the marks are so straight all the way down,.. maybe on a tight turn or something??

But,..I never mark the cable on the graph. I do mark the ball if going slow enough.

I have a couple e-mails out to Humminbird "pro staffers" but have not heard a thing back yet.

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Its usually air bubbles, it can also occur when u r in close proximity to another boat that has their gain turned way up. Check and see if the stacks occurred when u were speeding up or going with the waves and get a big push.

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I've had the same show up where I've marked it before and passed over the same area more than once...multiple times. I wonder if it is underwater structure...maybe even shipwreck materials? I've had it show up on flat water days too.

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I also suspect air bubbles, where the transducer in a wave is just too close to the motor. On a 16' boat, this may be the case, as you have a narrow 4'-5' beam. I would also suggest that you try the separate single frequency, and use about a 3/4 gain setting, no need for the maximum imho, unless you are over 250' fow.

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