Kayak Sonar Discussion

[chris138]

Originally Posted by Dirty Curti

Thanks for the thread. I have a few images I would like to share and get your opinion on what you see. I didn't catch any fish during these meter reads.


Thanks for any input.

Thanks for checking in. First off, were these taken in La Jolla near the corner or somewhere with similar structure? The reason I ask is some of it looks like kelp to me. But if you were in a sandy area with no kelp around I might reconsider.

#1: settings look really good in this one. To me this looks like a big school of fish... not huge fish but not tiny bait either. I've seen big schools of sandbass and calicos mark like this. Also, over rocky reef areas, you will see ocean whitefish and blacksmith perch look like this. Blacksmith or whitefish would explain why you never got a bite. I've seen big schools of yt look kinda like this, but they would be harder marks with a lot more bright reds and yellows in there.

#2: Sensitivity is way too high for that depth, need to dial it back a lot. Tough to tell what is there with all washed out like that, but I think I see your dropperloop or some bait down. And probably some baits and small fish checking it out.

#3 setting looks great. here we have a big vertical strand of kelp in the middle, and a couple of good wads of mackerel feeding at about 20-25'. Also some scattered debris and probably rockfish on the bottom. here you should be working that sibiki shallow, they look like good greenbacks or big spanish.

#4: shallow water again. Your sensitivity is a little hot, but much better than #2. The big worm in the middle is marking too soft to be a fish. With your gain up that high (bottom is super hot and top ten feet are washed out), a big fish or mammal would come back bright yellow in that shallow. However, in the bottom left of the shot, there looks like there was a good little wad of fish on the bottom. Could be some corvina, mackerel or small bass or something along those lines.

[Dirty Curti]

Originally Posted by chris138

Thanks for checking in. First off, were these taken in La Jolla near the corner or somewhere with similar structure? The reason I ask is some of it looks like kelp to me. But if you were in a sandy area with no kelp around I might reconsider.

#1: settings look really good in this one. To me this looks like a big school of fish... not huge fish but not tiny bait either. I've seen big schools of sandbass and calicos mark like this. Also, over rocky reef areas, you will see ocean whitefish and blacksmith perch look like this. Blacksmith or whitefish would explain why you never got a bite. I've seen big schools of yt look kinda like this, but they would be harder marks with a lot more bright reds and yellows in there.

#2: Sensitivity is way too high for that depth, need to dial it back a lot. Tough to tell what is there with all washed out like that, but I think I see your dropperloop or some bait down. And probably some baits and small fish checking it out.

#3 setting looks great. here we have a big vertical strand of kelp in the middle, and a couple of good wads of mackerel feeding at about 20-25'. Also some scattered debris and probably rockfish on the bottom. here you should be working that sibiki shallow, they look like good greenbacks or big spanish.

#4: shallow water again. Your sensitivity is a little hot, but much better than #2. The big worm in the middle is marking too soft to be a fish. With your gain up that high (bottom is super hot and top ten feet are washed out), a big fish or mammal would come back bright yellow in that shallow. However, in the bottom left of the shot, there looks like there was a good little wad of fish on the bottom. Could be some corvina, mackerel or small bass or something along those lines.

Great info thanks.

This is near the pipe in carlsbad.

Your comment regarding the "big worm" in photo 4 is to soft to be a fish. That confuses me because this is what I would expect to see if there is a larger fish under the kayak. So you said that if it was a bigger fish in water that shallow that I would see bright yellow color in the mark?

Also, Is there a way to understand a mark being on the left or right side of the kayak? Or where you should be casting when marks show up?

[chris138]

Originally Posted by Dirty Curti

Great info thanks.

This is near the pipe in carlsbad.

Your comment regarding the "big worm" in photo 4 is to soft to be a fish. That confuses me because this is what I would expect to see if there is a larger fish under the kayak. So you said that if it was a bigger fish in water that shallow that I would see bright yellow color in the mark?

Also, Is there a way to understand a mark being on the left or right side of the kayak? Or where you should be casting when marks show up?

Yes. The purplish return that you see there is probably some kind of kelp or debris floating midcolumn. If you were in 140' of water and saw that mark, I would say it might be a fish. But for how shallow you are in that pic, and how high your gain is set, a hard-bodied object would come back yellow, if not bright red/orange. Some may disagree with me... it's only my opinion.

You really can't tell which side of you the fish is on for the most part. I should note that its not impossible to tell, but its a very advanced technique without sidescan. The technique must be done with dual frequency, and requires a sideways oriented drift. The two sonar cones are not identical, and you can infer information from the overlap of the two signals. So if you drifted directly over an object (assume it's stationary) it would show up on 83 kHz first, then it would show up identically hard on both frequencies, then disappear from 200 and only be on 83 again. At this point you would know the object was on the upwind side as you drifted directly over it. If you practice this technique often, you can start to predict when the object will take this path. So once you just barely start to get the return on 200kHz, you can infer that it is down-drift from you.

Anyone follow that?

You can also slowly zigzag across an area and make similar inferences. Like I said, it's an advanced technique and takes 100's of "sonar hours" to be effective.

I had an idea for an invention which would have a dual spectrum return that could differentiate between port and starboard orientation. Anyone know an acoustic engineer?