fishfinder gain

[salmonquest]

I have a Garmin fishfinder 240. ON the last trip out I put the gain all the way up hoping to find the thermocline and/or bait fish. In water over 100' it started showing screenfulls of fish. at 150 fow and deeper we were getting readings of fish from 120 to 140. When I put the gain back to normal the fish symbols disapeared. Anybody know what might cause this phenomenon. I don't think the thermocline was that deep and I don't think there were that many fish but could it represent a temperature drop?

[Paulywood]

If you had the gain up to 100% it was probably showing every little thing as a fish. I just put in a Garmin 340c this year and have been running it at 87% w/ the fish symbols off. I am able to mark the thermocline and any bait or fish, seems to be working pretty good.

[salmonquest]

when you turn the fish symbol off does it just show the echo?? I was thinking about trying this.

[GLF]

I believe you need to have the fish symbol of in order to see the thermocline.

[Satisfaxion_Gauranteed]

I believe you need to have the fish symbol of in order to see the thermocline.

In the instruction manual on my Lowrance, it says to leave the fish symbol off to see more detailed information.

My Garmin manual says something very similiar; it strictly interrupts signal strength as fish. With the gain all the way up, everything will come back strong and be falsely interpretted as a fish symbol.

[Paulywood]

With the Fish ID off it shows fish as arches. I will try to find GLF's post of fish finder pictures and link it. I used to use the Fish ID but only when fishing with my girlfriend, she likes to see the fish pictures. With my Garmin at 87% I marked the thermocline the other week and downrigger balls, when they were close enough to the boat. Also had no problem marking bait balls.

[salmonquest]

Thanks this has been very helpful. I will definately make that adjustment next time out. Once again I'm sure all of your help should translate in more fish in the cooler

[GLF]

I think this is the picture Nick is referring to. Notice the arcs on it.

[Paulywood]

That's it Mike, thanks.

[salmonquest]

Yes I've seen that before on other fishfinders. Out of curiousity would a school of baitfish be a collections of small dots or small arcs?

[speeedman]

First I want to say the pic from GFL looks to me like the gain/sensitivity is set correct - if anything it could use a tick more - sometimes i will deal with some surface clutter for more gain - for a 15lb salmon you dont need alot of gain - for perch close to the bottom- more is better, or for seeing the thermocline, or if your looking for baitfish that are not in a huge ball/ i.e. loosely scattered - as per the question by Salmonquest GFL's unit does not look to be at 100% gain. You should not need 100% gain. Most screens would have way to much clutter to see anything. What I do see on the pic is the dark blotchy marks around the fish in the center of the screen. Also scattered blotchy marks elsewhere on the screen. I dont know for sure what it is, but my lawrance set on auto will not have a lot of that for a while then when the screen gets real dark, more so than GFL's pic, we smile. Seems fish like it. Could be a bunch of water fleas, temp change or loosely schooled bait, what ever we like it. When the screen gets dark like that continually its like someone turned the gain full bore. We will make a few passes through that stuff. GFL's pic has little surface clutter meaning the gain is not to awful high but does show the blotchy stuff meaning it is high enough to show the detail you want to see.

Fish symbols - do not use this feature ever, the only time you should is in weeds to seperate weeds from fish - that is what the manufacures say- my opinion - you better really know your sonar before you can tell the diffrence because I believe weeds will also show as fish symbols, not to mention air bubbles and crap suspended in the water. I have seen thousands of fish in fish mode, never caught one, the fish I seen with arches, well atleast I caught a few. You will never see a fish symbol come up to your bait, you will see arches come up and sometimes a pole goes off.

Gain/sensitivity - the older units you had to shut off the fish symbols and turn the gain up manaully to really use one correctly. The new units you can shut off the fish symbols and still be in auto mode for the gain, in auto the sonar will work very good as far as gain is concerned, especially on shallower water 40 or less but still works fine deeper. I fish no deeper than 90'. I try to turn my gain up 2 or 3 notches? If i go more I get to much surface clutter. I would say it is close to 90% but I would have to look to be sure. If I am busy setting poles or whatever and forget to adjust it up, I dont worry about it.

Thermocline shows well in auto or with it turned up, at up to the depth of 90' and more I am sure. The older units that you have to shut off the fish symbol and go to manual you will almost for sure have to turn up the gain to see it.

My 4 cents worth. Hope it helps.

[speeedman]

GLF I must apoligize for spelling your name wrong. GFL is in my head - GFL stands for Ganus Family Lofts - World famous racing pigeons, I have some of his birds. They are on the Indiana/Michigan border, some birds he sells go for more than a new 35' footer lol, not the ones I have.

Sorry for my mistake.

Steve

[GLF]

GLF I must apoligize for spelling your name wrong. GFL is in my head - GFL stands for Ganus Family Lofts - World famous racing pigeons, I have some of his birds. They are on the Indiana/Michigan border, some birds he sells go for more than a new 35' footer lol, not the ones I have.

Sorry for my mistake.

Steve

Not a problem Steve. The photo was from a nighttime Muskegon/Grand Haven trip I took earlier this year. The camera had problems focusing in.

[Joe von Grabe]

I highly recommend you attend one of Lance Valentine's seminar's on fish finders if you ever have the chance. I've used several different ones over the years starting with the paper graphs to my current Garmin color unit.

Going from memory:

1) Always have fish I.D. feature turned off.

2) Don't use the auto settings.

3) Manually adjust the gain as high as you can. If you don't have some interference showing, then your gain isn't high enough.

4) Large hooks (horizontally) don't mean large fish. It just means the fish moved within the cone.

5) Thicker marks, (vertically), means bigger fish.

6) Bait fish will show up as a blob, not small hooks.

7) If you see a blob with hooks around it, it's predatory fish feeding on the bait fish.

If you have a good quality fish finder with a color display, with the gain adjusted properly, you should be able to see the thermocline. What you actually see is the tiny zooplankton stuff that ends up at the thermocline. The thermocline is where there are two different densities of water that won't mix.

When I first got my Garmin, it was awesome to go out in the morning, see the thermocline on your screen with a bunch of hooks just below it, drop your riggers just above, and slam the fish. What's also amazing is that once the sun comes up, the hooks disappear.

Joe, "Sloppy Joe"

[Butch]

Plenty of good advice already but I thought I'd chime in since I also have a Garmin 240(used it tonight;)). Unless I'm in less than 45 FOW, I almost always increase the gain to "+3", and never use the fish symbols. Gain set at +4 is OK if it's calm and the fish are deep, +2 or +1 is adequate if I'm in less than 45 FOW. Fish will appear as discrete marks(not always as arches). Bait schools will look like a large black ball or a mountain rising off the bottom. Thermocline will usually look like a band of "clutter", which often wavers up and down or gets stronger and weaker. I also turn off the "auto range" if I'm in more than 100 FOW, and set it manually on 100, or on 150 if I'm interested in fish below 100 feet down.

Good Luck

Butch

[salmonquest]

Thanks for the great advice I've yet to get out to test it but I'll let you know when I do. I was thinking about the thermocline showing up well sometimes and then fading out. It makes sense to me that if the thermocline is showing up well defined it is probably due to a mass of organic material probably drawing in more bait fish and hopefully salmon. Would it make sense then to concentrate on areas with a well defined thermocline? Would this tend to be a convergence of current and temperature that would draw bait fish and salmon?