Help with the fathometer (fish finder?)

ANGLING ALLEN

Almost A Member
  • Apr 14, 2006
    212
    1,472
    Fullerton
    Name
    Larry
    Boat
    finatic
    Always called it "sonar" or "depth finder", even a "fish finder", but "yoursaltwaterguide" with Dave Hansen pointed out my shortcomings. LOL! Anyway for real. Gonna post a couple pics from a recent trip to Izors from the fathometer, what am I looking at? Thought it would be easier.

    Is this a bait ball? What are the line squiggles? What's up with the water temp? Hard bottom? Are any fish marking? Any help would be appreciated, be nice now...
    izors1a.jpg


    izors2a.jpg


    izors3a.jpg
     
    Upvote 0

    simmo13

    I Should Upgrade My Account
    Nov 12, 2010
    1,506
    705
    Lb inshore
    Name
    Simmo
    Boat
    19’ baja bayrunner!!!!!
    Bait balls and the third pic most likely suspended bass and barracuda, whitefish sheepshead. Its all out there
     
    Upvote 0

    MattFred1414

    Member
  • Jan 3, 2020
    514
    1,060
    27
    San Diego
    Name
    Matt
    Boat
    20ft Skeeter Zx20Bay
    Do you have any bones up there this time of year? It looks like something swimming through the range of you fish finder. I marked something like this right before we got into a thick pile of bones.
     
    • Like
    Reactions: onehottip
    Upvote 0

    J Woodman

    I know nothing
    Dec 8, 2006
    1,015
    562
    Ventura
    Name
    Jeff
    Boat
    15' Gregor "Silver Bullet", Parker 2310 "Deep Color"
    The red and black with a touch of red are probably bait. The squiggles look like your gain is up too high. Drop it down a little bit but not too much and they should go away. There may be a biter or a few outside that red bait ball.
     
    Upvote 0

    engelwurt

    Newbie
    Jul 6, 2016
    25
    31
    San Diego
    Name
    engelwurt
    Boat
    wurtdirt
    What unit are you using. Looks like you’re on high freq. Would be better at mid or low at those depths if you have them.

    First one definitely looks like bait, probably second one too. Third one looks like you have some suspended smallish fish. And all images show some noise/interference. The telltale sign is that the squiggles all have the same depth profile as the bottom. Probably would improve with lower frequency or maybe turning up the noise rejection or turning down the gain.
     
    Upvote 0

    TheMan90241

    Newbie
    Aug 28, 2012
    76
    202
    Downey/CA/Los Angeles
    Name
    Terry
    Boat
    Seaswirl Striper 2301 W/A
    I run Lowrance HDS sonar as well and have gotten pretty good at decoding all returns. Most of what is stated above is accurate. I have found that leaving the sonar on auto sensitivity will produce perfectly adequate results once you know what you are looking at and why you are seeing certain things. Here is my take on your images. In the first two, that is a bait ball of some kind. In many cases, you will also see more defined images in or around the bait ball which are feeding on the bait. The third or last image has much more information in it that you can learn from.

    Izors sonar diagram.jpg


    Different fish generally have a different signature based on their size, air bladder, and movement in the water. In Fig.A, this likely barracuda because it is higher in the water column and moving fast through the water. It leaves a long thin signature and is many times "S" shaped. Chances are, Fig.B and Fig.C are barracuda also since they tend to travel in schools, but it's worth noting they are slightly stronger or thicker of a signature. Fig.C is something you would typically see with bonito. Feeding calicos have a similar signature and can be high in the water column but the signature is generally shorter in length and thicker because they are swimming slower and covering less ground.

    Moving on to Fig.D, that is one of the rock piles at Izors. The reef is made up of many piles of concrete poles similar to the one pictured below. If I'm not mistaken, there are over 40 piles in that area and a few of them are about 15 feet tall. There is a great dive video at Izors that I took a screenshot from to show the bottom. Using Lowrance's side scanning feature does a great job of showing these piles on the bottom.

    Dive shot.jpg


    Fig. E does show a pretty clear line 15 feet above the ocean floor. I interpret this is as a single suspended fish that is not moving through the water. Because your boat is drifting slowly, it remains on your display a long time and is depicted as a long stretched out return. The targets in Fig.A, B & C are shorter and actually show signs of movement by their curved signature and changing depth either up or down.

    Lastly, Fig.F. There are a couple reasons for this type of image. My interpretation is they are a smaller type of bait fish that is not balled up like the first image. They are more spread apart. Just like in Fig.E they are stretched out as you drift over them at a slow pace. Because they are small targets, you could adjust your sensitivity gain to filter them out, but I would rather see the bait fish myself. Fish like these are clearly present in the dive video I was referring to earlier. The fact that the image is "mirroring" the contour of the bottom does not necessarily mean it is a poorly adjusted gain or "noise." The rocking of your boat or the movement of your boat from the swells will warp the image as well, all the images. For example, you could be on a perfectly flat bottom, but it will appear wavy due to the rocking of your boat. And there is definitely something wrong with your temp sensor. Go into your sonar menu under installation and make sure you have selected the correct transducer. Something doesn't jive there.

    Once again, it is just my interpretation and experience that forms my opinion. You will figure out the personality of your sonar the more you use it and draw a correlation between what you see and what you catch. Hope I didn't bore anyone to death!
     
    Last edited:
    Upvote 0

    MYNomad

    Heading South
    Dec 12, 2007
    4,177
    4,776
    Pacific Northwest / West Coast Mexico
    Name
    Rick
    Boat
    Yes
    FWIW, you are fine with high frequency at that depth, and your gain is not too high. Displaying high and low frequencies side by side allow you to get a little more information since the high frequency cone angle is more narrow than that of the low frequency. Identifying specific species is, IMO, more art than science but identifying bait (not the species, just that it is bait, although squid is distinctive), especially when it's balling, is pretty easy. And everything else is a predator that may be worth catching.
     
    • Like
    Reactions: TheMan90241
    Upvote 0

    DaveyK

    Trying to Learn
    May 29, 2020
    40
    23
    29
    Los Angeles
    Name
    Dave K
    Boat
    n/a
    I run Lowrance HDS sonar as well and have gotten pretty good at decoding all returns. Most of what is stated above is accurate. I have found that leaving the sonar on auto sensitivity will produce perfectly adequate results once you know what you are looking at and why you are seeing certain things. Here is my take on your images. In the first two, that is a bait ball of some kind. In many cases, you will also see more defined images in or around the bait ball which are feeding on the bait. The third or last image has much more information in it that you can learn from.

    View attachment 1206035

    Different fish generally have a different signature based on their size, air bladder, and movement in the water. In Fig.A, this likely barracuda because it is higher in the water column and moving fast through the water. It leaves a long thin signature and is many times "S" shaped. Chances are, Fig.B and Fig.C are barracuda also since they tend to travel in schools, but it's worth noting they are slightly stronger or thicker of a signature. Fig.C is something you would typically see with bonito. Feeding calicos have a similar signature and can be high in the water column but the signature is generally shorter in length and thicker because they are swimming slower and covering less ground.

    Moving on to Fig.D, that is one of the rock piles at Izors. The reef is made up of many piles of concrete poles similar to the one pictured below. If I'm not mistaken, there are over 40 piles in that area and a few of them are about 15 feet tall. There is a great dive video at Izors that I took a screenshot from to show the bottom. Using Lowrance's side scanning feature does a great job of showing these piles on the bottom.

    View attachment 1206033

    Fig. E does show a pretty clear line 15 feet above the ocean floor. I interpret this is as a single suspended fish that is not moving through the water. Because your boat is drifting slowly, it remains on your display a long time and is depicted as a long stretched out return. The targets in Fig.A, B & C are shorter and actually show signs of movement by their curved signature and changing depth either up or down.

    Lastly, Fig.F. There are a couple reasons for this type of image. My interpretation is they are a smaller type of bait fish that is not balled up like the first image. They are more spread apart. Just like in Fig.E they are stretched out as you drift over them at a slow pace. Because they are small targets, you could adjust your sensitivity gain to filter them out, but I would rather see the bait fish myself. Fish like these are clearly present in the dive video I was referring to earlier. The fact that the image is "mirroring" the contour of the bottom does not necessarily mean it is a poorly adjusted gain or "noise." The rocking of your boat or the movement of your boat from the swells will warp the image as well, all the images. For example, you could be on a perfectly flat bottom, but it will appear wavy due to the rocking of your boat. And there is definitely something wrong with your temp sensor. Go into your sonar menu under installation and make sure you have selected the correct transducer. Something doesn't jive there.

    Once again, it is just my interpretation and experience that forms my opinion. You will figure out the personality of your sonar the more you use it and draw a correlation between what you see and what you catch. Hope I didn't bore anyone to death!
    this is the best 101 walkthrough i've read. Thank you.
     
    Upvote 0

    GregAndrew

    I Find Stuff
    Dec 28, 2008
    719
    700
    San Gabriel,Ca.,USA
    Name
    Greg
    Boat
    T15 Kayak
    Lots of good info here. I would argue that you can tell what type of bait by the return (to a certain depth scale). And lots of things that look just like "bait balls" are not bait at all. I would bet dollars to donuts that the bait ball in the first pic is a mixed school of Sardines (looking for orange/yellow blobs), probably with Spanish (blue with short marks). Most of the marks between there and the bottom are slow movers like blue perch, blacksmith perch and whitefish (among other reef fish) that you will find around almost any structure in SoCal. If you needed to make bait, I would skip the ball in the second pic. They are not likely bait fish if they are that close to your transducer and none of them are producing more than a blue dot (blue streaks, even if short, are a different story). However, several things can change the look of any particular mark. Density of a school, whether the mark is or is not in the main cone angle, distance from the transducer, depth scale, frequency, sensitivity, colorline etc.
     
    Upvote 0

    RyanErb

    Love to fish!
  • Aug 7, 2012
    1,732
    915
    All over the 805
    Name
    Ryan
    Boat
    OnTheWater
    Well everything that needed to be said pretty much already was, but sonar definitely shows ideally in a slow idle, think like 2-5mph. If you are drifting, or anchored, it's a little tougher to decipher. Don't forget there are a ton of youtube videos out there explaining sonar as well, be sure to watch a few. Best thing is to drop something over the side, maybe some squid or small swimbait and see what you catch and you will start being able to understand what you are seeing based on what you pull in, etc.
     
    • Like
    Reactions: the SLIDER
    Upvote 0

    invictus

    AVD
    May 26, 2006
    4,484
    2,184
    Orange County
    Name
    Jason
    Boat
    Tiara 2000 Cuddy
    What has hleped over the years is playing with settings, dropping on marks and seeing what is caught, and diving/snorkeling shallow spots so my brain can decipher what the screen shows me.

    Putting my eyes on it, that works.
     
    Upvote 0