Sonar issue, Shallow downriggers.

[ondarvr]

Over the last few years as I've fished for Sockeye and Kokanee more, I've experienced something that I hadn't in the prior 50 years of fishing.

There is a situation that takes place due to how you fish for these species that doesn't come into play when trolling for other Salmon or trout.

At times you are trolling very slow and relatively shallow, 20 to 30' and what ends up happening is the return signal from the DR balls is strong enough that the Fish Finder determines it must be the bottom and reads them as the actual depth, but the real depth might be 100'. Then the unit will only show things above the DR balls.

The problem is these fish can like very low trolling speeds, from .75 to 1.75MPH is common, at these low speeds the DR balls are directly below the boat, there is little or no blow back. The current crop Fish finders are much more sensitive than in the past, plus they may have dual beam transducers, this all combines to create the problem. A couple of people said it must be the brand of unit I have, but I tend to be the one adjusting the units on other peoples boats and in these fisheries they've had the same problem with different brands.

I have asked many knowledgeable people about this and the answers were a bit surprising, the "experts" had never really experienced it, some even said it couldn't happen and I that had my settings all wrong. I'm someone that reads the manual 10 Xs and takes it with me to set things up on the water, then goes online to find tutorials on the subject, so far I've found nothing. But, here are my solutions.

If you want you can try the wider sonar beam, this will give the unit a larger cone area at the shallow depth where the balls are, which may allow the unit to look past the balls. This works many times, but I don't like how the screen reads using the 50 or 83 beam, the narrow 200 beam gives better returns.

Another solution is to angle the transducer slightly forward or back, this puts the balls off to the side of the cone so their return isn't as strong. You can still see the balls, and it will still read the bottom.

The other thing that helps is longer DR booms, at 20 to 30' the cone is small, so just getting a little more reach can solve it. This works OK with 2 DRs, but with a third in the middle it may still be an issue, it is for me.

What solved it completely is when I went to an electric Minn Kota i-pilot with a transducer built into the motor housing, it moves the transducer far enough forward and away from the balls that sometimes they don't even show up on the screen, I don't like this but some people do.

This becomes more of a concern when the 2 rod endorsement comes into play, in an attempt to get 8 rods in the water you may need to use DR's more often even when trolling shallow.

One reason some the experts and instructors (I asked the good folks at Lowrance when I attended the class) don't know about it is because they are normally fishing from larger boats at higher speeds, so even if they fish shallow their speeds are higher resulting in more blow back, so the balls aren't straight down. Plus their boats may be bigger (wider) with longer DR booms.

I hope this helps, plus if anybody has better solutions let me know.

[Nelly]

Hey O,
Thanks for thoughts on this issue and I've experienced it as well. Usually I can "see" beyond the balls by adjusting the sensitivity and going to a manual depth range.
Overall I've seen many more mid-water targets by running Structure Scan due to its wide beam characteristics.
Thanks again for your post, its great to hear others sonar stories!

[Smalma]

Ondarvr -
Great topic; down rigger ball "black-out" can be really frustrating for the small boat angler targeting kokanee and sockeye.

I too could not get any satisfaction from my manuals or find advice that lead me to a quick solution. A couple years ago when I upgraded to a Elite 5 I was able to eventually find a combination of settings that allow me to effective target kokanee and sockeye. It took approximately 4 hours of trail and error before I stumbled on a combination that allow be to consistently see the targets above and below the downrigger ball - an absolute requirement to adjusting depths to respond to fish movements over the course of a fishing day.

Needless to say no one touches the unit now that I have it "dialed in". While those settings allow me to track the fish depths it does have some drawbacks - loss the downrigger ball marks at 40 to 45 feet and at running speeds (anything over 12 or 15 mph) the unit can not find the bottom at depths greater than 60 feet or so. Not ideal but workable.

There has to be an easier way but have not found it or even some serious discussion of the issue. Though to be fair when it comes to these types of issues I seem to be exceptional dense (an age thing?).

Curt

[Dan Carney]

I too have experienced this issue while fishing for kokanee and sockeye. I went for a lower tech solution. I retired the 8lb balls I was using and went down and got some 3lb weights. Then I drilled a small hole and added an eye screw. Now I have two 3lb downrigger weights which have some blowback at 0.8 mph sog and problem solved. This even works when I am just 5 or 10 feet down on the rigger.
L8R
Dan

[Sharkey45]

I totally agree with Dan. I use 4lb balls for kokes and I haven't had an issue.