Sonar Interpretation

RD

Kung Fu!
We've been fishing a Western Washington reservoir the past few weeks and I'm wondering if anyone has any insight into the sonar picture. The fish are generally 20-25 feet deep and the surface temperature is 45 degrees. There is a red band on the screen where the fish are located. When we clean fish, either the stomachs are empty or we find daphnia (sometimes sticks and small rock). Could the red layer be a band of daphnia?

P1080120.JPG
 

Buzzy

Active Member
Interesting question about daphnia. A lake I fished once this spring seemed to have a "layer" maybe 8 or so feet below the surface and it didn't go all the way to the bottom. A friend of mine is convinced we're looking at daphnia on our Fishin' Buddies (which likely don't have near the capability of your sonar unit). Somehow I'd think there'd be more than small bands - more like large clouds but this is supposition on my part.
 

Smalma

Active Member
Looks more a fish to me; maybe a mixture of juvenile salmonids (kokanee/coho?) and larger fish.

The Daphnia should not be making a strong signal or mark. The daphnia if showing up on the screen are more likely to look like a defused haze. The stronger marks are typically an echo return coming off the bladder of the trout. Given the small size of daphnia, lack of a bladder, etc. they should not make much of a mark. Have spend a lot of time fishing kokanee which are feeding primarily on kokanee and never seem to mark what I think are daphnia.

Do the marks stay at about the same level through out the day? The daphnia during the night migrate to the surface and then with daylight move slowly back to depths; the haze higher in the water column the first part of the morning.

Curt
 
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RD

Kung Fu!
Looks more a fish to me; maybe a mixture of juvenile salmonids (kokanee/coho?) and larger fish.

The Daphnia should not be making a strong signal or mark. The daphnia if showing up on the screen are more likely to look like a defused haze. The stronger marks are typically an echo return coming off the bladder of the trout. Given the small size of daphnia, lack of a bladder, etc. they should not make much of a mark. Have spend a lot of time fishing kokanee which are feeding primarily on kokanee and never seem to mark what I think are daphnia.

Do the marks stay at about the same level through out the day? The daphnia during the night migrate to the surface and then with daylight move slowly back to depths; the haze higher in the water column the first part of the morning.

Curt
That was useful. The red marks seem to be within the school of fish. I seem to recall hazy reflections near the surface early in the morning, but I figured that was from wave action. The sonar is in autopilot mode.
 
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RD

Kung Fu!
Looks more a fish to me; maybe a mixture of juvenile salmonids (kokanee/coho?) and larger fish.

The Daphnia should not be making a strong signal or mark. The daphnia if showing up on the screen are more likely to look like a defused haze. The stronger marks are typically an echo return coming off the bladder of the trout. Given the small size of daphnia, lack of a bladder, etc. they should not make much of a mark. Have spend a lot of time fishing kokanee which are feeding primarily on kokanee and never seem to mark what I think are daphnia.

Do the marks stay at about the same level through out the day? The daphnia during the night migrate to the surface and then with daylight move slowly back to depths; the haze higher in the water column the first part of the morning.

Curt
That was useful. The red marks seem to be within the school of fish. I seem to recall hazy reflections near the surface early in the morning, but I figured that was from wave action. The sonar is in autopilot mode.
 

wanative

Retired, gone fishin'
WFF Supporter
That was useful. The red marks seem to be within the school of fish. I seem to recall hazy reflections near the surface early in the morning, but I figured that was from wave action.
Turn off the auto mode and run your unit on manual settings.
Set the depth range to slightly deeper than the depth your fishing in. Turn down or off the surface noise filter feature.
Adjust the gain (sensitivity) to strong enough that you get a double echo (you'll see two bottoms, the real one and the "double echo"). Then back the sensitivity down to make the "double echo" disappear showing only a strong bottom return.
Your unit should then be set at the correct sensitivity for the depth your fishing. The fish will appear as arches such as these sockeye salmon. 20170805_105933.jpg 20170805_105957.jpg
The more faint mark's are fish further away from the center of the transducers
cone or smaller fish. Sockeye and kokanee have large air bladders and the air causes a real strong return on your unit indicated by the bright yellow in the arch.
Trout often show only as a colored arch being brighter the closer to the center of the cone angle they are.
In my two photos the horizontal lines are the echo returns of downrigger balls and flashers tracking through the water column.
Depthfinders filter a lot of detail when auto settings and noise filter settings are set high. Probably not as bad in newer units as older ones as technology keeps improving.
The shallower you fish the lower the sensitivity needs to be to get good returns.
I fished yesterday with my Garmin Stryker 4 in 18 to 30 feet depth and a sensitivity setting of 85 to 88% was giving great returns.
 
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Jim Travers

Active Member
Set the depth range to slightly deeper than the depth your fishing in. Turn down or off the surface noise filter feature.
Adjust the gain (sensitivity) to strong enough that you get a double echo (you'll see two bottoms, the real one and the "double echo"). Then back the sensitivity down to make the "double echo" disappear showing only a strong bottom return.
This is how you adjust!!! TURNIN knobs!!! Adjust for the premier settings. This IS the appropriate protocols to be used in these sonar premier settings type situations
 

Clarkman

Huge Fly Guy
WFF Supporter
Being really new to this whole utilizing electronics & being the relatively recent owner of the Garmin Striker 4, these types of threads are really helpful. Currently, for muskies, I don't think I need to change much from auto with a medium sensitivity setting, but this spring when I get after smallies, I'll probably have to play around with things a bit more. I use it mostly for structure currently anyway, but it would be nice to utilize more of the features on it.
 

Canuck from Kansas

WFF Supporter
Cheaters! Whats wrong with paddling/motoring around aimlessly without a clue, it's pretty much how I go through life, so why not fishing?:D Note of admission, I am almost exclusively a small stream fisherman without any sort of floating device.

Cheers
 

Chucker

Chucking a dead parrot on a piece of string!
Those are just fish. Not daphnia.

Exactly. Fish moving slowly across your sonar cone. Two large fish on the left of the screen, 4 or 5 smaller fish on the right. It really just proves that the “fish I.d.” feature is useless unless you are moving at a steady 3-5 mph trolling speed.

Daphnia don’t generally form a layer anyway. They are usually in discrete swarms which would show up as a large blob in your sonar if the sensitivity was set high enough.
 

zen leecher aka bill w

born to work, forced to fish
Interesting question about daphnia. A lake I fished once this spring seemed to have a "layer" maybe 8 or so feet below the surface and it didn't go all the way to the bottom. A friend of mine is convinced we're looking at daphnia on our Fishin' Buddies (which likely don't have near the capability of your sonar unit). Somehow I'd think there'd be more than small bands - more like large clouds but this is supposition on my part.

If the fishfinder is set up to show signal return as arches daphnia will show up as a speckled cloud on the screen. If the fishfinder is set up to show fish icons daphnia when thick enough will show up as smaller fish icons when they are dense enough to return a signal. There's a local lake where the trout eat crayfish and daphnia. The screen shows a big band of "mush" and then fish arches above the "mush". The "mush" is the giant daphnia school and the arches are the fish above that layer.

Originally we thought we were looking at the previous year's weeds above the bottom but after a little thought realized weeds would not grow in 40-60 feet deep water. It had to be something else. We ended up with daphnia. Stomach samples bore this out.
 

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