Lowrance DownScan – “Gimmick?”

After quite an interesting week of debate on local and international forums, one of the issues that came up was “Is Down Scan really a fishing tool, or is it just pretty pictures?” Targeting deep water structure can be a bit daunting because you can’t physically see what you are fishing. That is where structure detail and target separation come in. Take these images below for example. The first pass over this tree (left) showed a good shoal of bass close together sitting just above the thermocline at 50ft. But 3 minutes later when I passed over it again, the shoal had moved right near the bottom some 15ft deeper, and were slightly more dispersed. Some of you reading this must be thinking that I must be seriously miss-informed thinking that bass live that deep, take a look at this video I recorded some weeks back. YouTube – Lowrance DownScan with John Easton

Knowing how shoaling bass are moving around within major structure is very valuable information. This was never possible before with conventional 200kHz sonar, or even 83kHz Broadband for that matter, due to the umbrella effect of the arches made by the sound waves hitting the branches.

For those of you following the forums, local and abroad, you will know by now that the secret to impressing everybody with high frequency sonar is to take screenshots of very large objects like bridges and big trees. The ‘Home Tree’ in the latest block buster movie Avatar would be a wonderful subject. But what about smaller trees, and brushpiles?

Driving around a relatively baron area just south of Ernies Bay point (Slipweigh), I came across this tree lying on the bottom at a depth of 39ft. There are literally hundreds of these trees lying around Inanda Dam, but this one was different. There was a thermocline slap bang in the middle of the tree at 36ft, and just above it were 2 little dots.

Knowing what I know about bass and how they relate to structure, these had to be two bass. So it was time to send my little underwater camera down on my marker buoy line again. After retrieving the camera, and playing the video back, you can just imagine how I felt when I saw these two bass. The only thing that impressed me more than the bass, was the accuracy of the DownScan screenshot representation of this tree.

As a freshwater off shore angler, this is the most powerful and amazing tool I have ever had the privilege of owning.

John,
What do you think about the small white dots in your vertical tree? They have moved in the second photo. Do you think they are also fish? Since traditional sonar shows trees with arches like fish arches and DownScan shows fish as white dots, is it possible a tree will show up with white dots and not be fish? Since you have been looking at trees, if most of your DownScan photos of vertical trees don’t show white dots that would help answer this question. The best way would to locate a tree without dots and one with dots and drop the camera. The reason I am wondering is we have standing trees in the Missouri River that have walleye in them that we catch. It would be nice to be able to select the best trees for trolling before I start. I will figure this out this summer but you live in sunny SA and have the tools and passion to solve this for me.
One more question, tell me about your underwater camera, the background is green and the bass show up well in 35 feet, what model do you use?

Doc,
The structure is basically a whole lot of ‘little white dots’ making up the tree in this case. My rule of thumb is if the little white dots are suspended, then there is a good chance that it is fish. If your tree seems to look like its got a whole lot of Xmas lights in it like mine in the standing tree example, the first step would be to turn the contrast down to about 60. If they all diappear, then they are probably not fish, but if some little lights remain, then those are probably fish.

I troll a lot too, and since I’ve had DownScan, I won’t even attempt a run with lures out unless I’ve checked it out first with DownScan and 83kHz split screen. It works!

My last camera, the Pentax Optio W20 is only meant to go to 6ft, but after several years of abuse at +40ft it has finally packed up. I now use the Canon PowerShot D10.