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Thread: Determining fish size with Side Imaging...

  1. #1
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    Default Determining fish size with Side Imaging...


    One thing I have learned while using SI is how to determine fish size. Crappie on SI don't reveal a large return because they are a small fish (of course) but also because of their shape. If you think about SI and how it is a thin beam that when objects are scanned they return a signal. I try to think about it this way.. Think about a water fall of smooth flowing water. If you stick a football (representing a striped bass) in the waterfall you will make a pretty big hole in the wall of water. If you stick a frisby vertically (representing a crappie) in the waterfall you will have much less of a return due to the thickness and shape. I believe the same holds true to fish size and returns on SI. The football size thick fish will return a larger round dot and cast a nice shadow in SI. The vertical frisby shaped fish will return a much smaller dot and small shadow (if any). Just something to keep in mind. Also remember to compare size to scanned distance. If you are scanning 100 feet, your returns will be much smaller than scanning at 50 ft.

    Gar seem to return a long return since they are long hard fish. Catfish seem to return your biggest and brightest returns since they are long, hard, and FAT!.

    Below are some examples of fish type. Most of these are confirmed by catching them. The gar images are confirmed by visually seeing them rolling all across the surface. The catfish images have not been confirmed but I feel pretty sure about them.

    Striped Bass









    Gar











    Crappie













    Catfish







    DoubleG

  2. #2
    Cane Pole's Avatar
    Cane Pole is offline Crappie.com 2011 Man of the Year * Crappie.com Supporter
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    I useta use a program called yellowfin. I could even measure the height of stumps. I believe it was based on length of shadow and distance from boat. Lost interest.
    Member BS Pro-Staff and Billbob Pro-Staff
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    How come you can see the Bass and catfish off the water column, but the crappie you cant. Is that because of size also? Oh yeah great shots.



    MEMBER CRAPPIE MAFIA

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    RCC is offline Crappie.com Legend and Arkansas Moderator
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    Great shots and great job interpreting the return. I'm not that good myself, but can sometimes tell crappie by the shape of the school of fish.
    RCC's Crappie Eradication Service
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    great pictures, maybe one day I'll get a screenshot like those. Very nice. I've read where the size of the shadow generated is a good indicator of the size of the fish
    GO BIG ORANGE !

    I meant to behave, but there were just way too many other options available at the time.

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    great pictures

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    Thanks for the great pics and explaining what we're seeing. These are by far the best SI pics I have seen on any forum! Look forward to more!! Thumbs Up
    CATCH A BIG-UN

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    Cane Pole is offline Crappie.com 2011 Man of the Year * Crappie.com Supporter
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    Quote Originally Posted by slabbandit View Post
    Thanks for the great pics and explaining what we're seeing. These are by far the best SI pics I have seen on any forum! Look forward to more!! Thumbs Up
    Yep. I like the last shot the best.
    Member BS Pro-Staff and Billbob Pro-Staff
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    Thanks fellas... I appreciate it. These are some of my best images. I have over 1100 right now. That last one was taken with my 898 before I upgraded. It was super cold that day and I just decided to ride around and explore and found that big group of fish. I was amazed.. I need to get some cut bait and try to catch one of those big rascals this year... I am just usually too busy chasing crappie to switch to catfish.

    DoubleG

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    On Doublegobble00's pics, what does the green arrow represent? Sometimes it's pointing left and sometimes it points to the right.
    CATCH A BIG-UN

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