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Thread: How to use a fish finder?

  1. #1
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    Default How to use a fish finder?

    How do you guys/gals use your fish finders on the ocen?
    If you stop somewhere to fish for rockfish or halibut and the fish finder does not show anythig, do you still drop the line, or not?
    What about salmon, is it any use to chase salmon with fish finder? Or are you just looking for scools of fish and determine the depth with your fish finder?
    I am not sure how much area(cone?) the fish finder covers on the screen, that's why I have not been able to make very good use out of it, except for checking the depth.
    Thanks
    Vadim

  2. #2
    Member DRIFTER_016's Avatar
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    The most common transducer cone angle is 20 degrees, the deeper the water the larger the area inside the cone. When I'm fishing I look for structure (humps, dips, drop offs, rock piles etc.) and bait (shcools of herring, ciscoes etc.) I also look for the thermocline (thin band of water with rapidly changing temperature) it usually shows up on good qualty sonars as a grey/black band somewhere in the middle of the water coloumn. I let the temperature and bait tell me what depth to run my lines for salmon. As for halibut, use your sounder to find the humps and structure the hallies like and fish. You will be hard pressed to see the fish with any but the best sounders due to their relationship with the bottom. If you are not seeing fish while hallie fishing I would fish a spot for a while and if nothing happens change your location and try again. Unless the fish are suspended you won't see them on your finder. Once you get good at reading your sonar you will be able to mentally picture the bottom in 3D. As a Lake Trout guide in the NWT I spend hundreds of hours a season staring at my finder looking for the next world record.

    Here's a good tutorial on sonars and their use.

    http://www.lei-extras.com/tips/sonartut/Default.asp

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    since Hali don't have a swim bladder...you never see them suspended or not.

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    Member SkinnyRaven's Avatar
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    Quote Originally Posted by Cutter View Post
    since Hali don't have a swim bladder...you never see them suspended or not.
    Are you saying a sound wave will only echo off a swim bladder?

    07 Ocean Pro 220 ET HT
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  5. #5

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    vadimb, what unit are you using? what kind of power has it got? for serious saltwater use I like a minimum of 500w (RMS) or 4000w (PtoP), 300 will work, anything less is a toy meant to be used in shallow, fresh water. Spend as much time as you can with the manual in your lap while pressing buttons and figure out what everything does, it probably does alot more then you realize.
    I live and die by mine for both salmon and bottom fishing. When I pull into a salmon spot I like to motor around and see what is there, basically, I want to see feed, if there is bait present its pretty likely the fish aren't far away, I don't have to mark fish just bait, if I don't find it, I'm probably not staying.
    When I'm bottom fishing I like to use either bottom lock or bottom zoom, reason being, if I'm in 300' of water I'm basically just interested in the bottom 20', I really don't care whats happening in the top 280', you also won't get much bottom detail or see many fish unless your zoomed in on bottom. Fish will not appear as arches when your zoomed in, they'll now appear as spikes coming off the bottom, if your screen is filled with spikes, you might want to drop lines. Once you've spent some time learning the zoom features you'll learn bottom features and know what kind of structure to look for.
    I guess the biggest piece of advice I can give is, put in the time and read the manual, alot. I've been using the same Furuno FF for over 10 years and I'm still learning things about it.
    Good luck.

  6. #6
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    Default Where do you fish on the thermocline

    Quote Originally Posted by DRIFTER_016 View Post
    The most common transducer cone angle is 20 degrees, the deeper the water the larger the area inside the cone. When I'm fishing I look for structure (humps, dips, drop offs, rock piles etc.) and bait (shcools of herring, ciscoes etc.) I also look for the thermocline (thin band of water with rapidly changing temperature) it usually shows up on good qualty sonars as a grey/black band somewhere in the middle of the water coloumn. I let the temperature and bait tell me what depth to run my lines for salmon. As for halibut, use your sounder to find the humps and structure the hallies like and fish. You will be hard pressed to see the fish with any but the best sounders due to their relationship with the bottom. If you are not seeing fish while hallie fishing I would fish a spot for a while and if nothing happens change your location and try again. Unless the fish are suspended you won't see them on your finder. Once you get good at reading your sonar you will be able to mentally picture the bottom in 3D. As a Lake Trout guide in the NWT I spend hundreds of hours a season staring at my finder looking for the next world record.

    Here's a good tutorial on sonars and their use.

    http://www.lei-extras.com/tips/sonartut/Default.asp

    So when you see the Thermocline where do you drop your line for the salmon... on top, in it or under it?

  7. #7
    Member akfun's Avatar
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    i have seen suspended halibut around my boat visually and on my sounder they show up as a group of small echos, if you are using the fish id somtimes they do not show up as anything other than a few pixels shaded. depending on your screen they may be just 1 or 2 dots. i did not know this until last year when i had halibut around my boat. just my thoughts.jeff

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    Member DRIFTER_016's Avatar
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    When fishing a thermocline I run my lines at the top. Fish will almost always move up for a bait but will almost never move down,

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    Member pike_palace's Avatar
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    Default it depends on the fish

    Well if your looking for Halibut or Rockfish or lingcod, your going to be looking at what type of bottom there is rather than fish. Salmon your looking for schools of baitfish. That seems to work good.
    "Ya can't stop a bad guy with a middle finger and a bag of quarters!!!!"- Ted Nugent.

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    skinny - I'm saying that a fish finder tags a fish by virtue of that fish having a swim bladder. The wave is distorted when passing through the fish, not bouncing off it like it does with the bottom. A large fish will get hit twice (one the way down and then up) and show up on your finder as two fish very close together.

    Feel free to dispute if you want

  11. #11

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    I mark kings on my fish finder all the time. I run a duel frequency (50/200) and I can tell what is in an area in a hurry. Coho's show up really well too.

    Rockfish are very easy to see. They can be confused with bait sometimes and you'll figure out really quick it's rockfish. Ling looks different than rockfish.

    Halibut are tricky, but I've marked them and thought they were kings.. until I've hooked into them. When they are on the bottom, I don't mark them. I'm going to work on trying to mark them though as it would be helpful.

    I've also found that things look different on different units and brands. I just started jigging up what I marked to figure out what was what.

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    for the record - ling do not have a Swim Bladder either....so while you think you are seeing them on your finder....your probably seeing the fish they just ate, and the same for halibut.

    I highly doubt you know what fish you are seeing on your finder....you are only really ever guessing.

    If there is some kind of new technology out there (that us average jo's can afford) that can tell you what fish it is you are seeing....then I'll stand corrected

    until then - I'll keep guessing what those arches are - and hoping they are what I am targeting

  13. #13

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    so then halibut and lingcod are completely un seeable on a fish finder cutter?

    Interesting.....mind going into more detail as why?

    I do know the simrad we used when I deckhanded would come back with different colors for different fish due to it's airbladder but it would still mark fish with or without airbladders. Could very easly tell the difference between rock fish or salmon and even amongst rockfish due to the different colors. Could it have been reading lingcod? I bet it could but couldnt tell for certain.

    I have read though of guys over in dutch long liners seeing halibut stacked and being able to see them on fish finders as layers just as you'd expect to see them.

  14. #14

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    Quote Originally Posted by Cutter View Post
    for the record - ling do not have a Swim Bladder either....so while you think you are seeing them on your finder....your probably seeing the fish they just ate, and the same for halibut.

    I highly doubt you know what fish you are seeing on your finder....you are only really ever guessing.
    Haha... OK, just keep believing that. The rest of us who are "guessing" will keep filling up the boat.

  15. #15

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    Quote Originally Posted by TradBow View Post
    so then halibut and lingcod are completely un seeable on a fish finder cutter?
    During the winter I troll for kings. I mark balls of narrow squiggly lines on the bottom in certain areas. EVERY time I drop down to fish those marks, I catch a 15-20" lingcod. So yes, you can mark lings and they look very distinct from everything else.

  16. #16

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    A school of late march kings....

  17. #17

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    crappy pic as it was originally on my cell phone, but you can see the king in the feed ...


    BTW, the king tasted great. (January king) Good thing I "guessed" that was a king!

  18. #18

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    270ti -

    Man, I've got to figure out what I'm doing wrong. I have a Lowrance duel-frequency color sonar (looks similar to your picture) and have never been able to dial it in so that it works as well as I'd like. Are you using factory settings, or did you have to tweek it a bit? Of course it never looks as good as it does when you have it on Demo mode

  19. #19
    Member SkinnyRaven's Avatar
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    Default I'm Not Saying You're Wrong

    Quote Originally Posted by Cutter View Post
    skinny - I'm saying that a fish finder tags a fish by virtue of that fish having a swim bladder. The wave is distorted when passing through the fish, not bouncing off it like it does with the bottom. A large fish will get hit twice (one the way down and then up) and show up on your finder as two fish very close together.

    Feel free to dispute if you want
    I have heard the reasoning before, however I do not know it's origin as I have never seen mention of it in any research I have done on Sonar. I can use my sonar to determin the depth of my downriggers, and with the Fish ID on the weights will show as a line of fish. The arches displayed without Fish ID echo the profile of the fish, hense the arch. A Halibut would display as a flat line or a flattened arch. The issue with sonar is the resolution in vertical pixals. The more vertical pixals the beter the resolution in deep water. 320 vertical pixals in 320' of water would display one foot of water depth per pixal, takes a masive fish to echo an arch at those depths. Not sure that the zoom feature does anything but inlarge the view. If you can point me to information regarding the swim bladder I'll be more than happy to review it.

    http://www.lei-extras.com/tips/sonartut/howitworks.asp
    In the simplest terms, an electrical impulse from a transmitter is converted into a sound wave by the transducer and sent into the water. When this wave strikes an object, it rebounds. This echo strikes the transducer, which converts it back into an electric signal, which is amplified by the receiver and sent to the display. Since the speed of sound in water is constant (approximately 4800 feet per second), the time lapse between the transmitted signal and the received echo can be measured and the distance to the object determined. This process repeats itself many times per second.

    As mentioned earlier, the sonar unit sends and receives signals, then “prints” the echo on the display. Since this happens many times per second, a continuous line is drawn across the display, showing the bottom signal. In addition, echoes returned from any object in the water between the surface and bottom are also displayed. By knowing the speed of sound through water (4800 feet per second) and the time it takes for the echo to be received, the unit can show the depth of the water and any fish in the water.

    07 Ocean Pro 220 ET HT
    115 Yamaha
    Garmin 740S, GMR 18 HD
    Airmar TM 260-MM

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