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No fish arches here either on my Lowrance unit. Just learn to id fish when they show up. I think those arches can be seen in perfect conditions, like fresh clear water, no swells or chop and 0 speed.
__________________ 161 AquaSport Power Cat / Merc. 9o
"50,000 battered women and I'm still eating mine sushi style!!"
According to the "sonar tutorial" Lowrance puts out, you have to be moving at a slow but steady speed relative to the fish, and have the fish go through the approximate center of your sonar cone.* The fish is at a greater distance from your transducer when it is at the edges of the cone, and closest when the fish is directly under the transducer.* It makes sense to me.*
__________________ PAX River, MD
Fisheye
Channel 69
On only one or two occassions have I seen arches on my Furuno fish finder. Theoretically, a fish will be "painted" as an arch if the relative direction and speed of the objects are constant - but in real life it's not likely to happen too often.
Most of my fishing is shallow water, 75' or less. Decent fish arches at this depth are pretty easy to obtain at rest or trolling speeds. I don't have any real experiance with deep water though. Mostly it seems to be a matter of having sensitivity set low enough that you get a bit of surface clutter. A fishing buddy has a lowrance unit and we have good success getting arches when targeting stripers. My Sitex Profish III is a little trickier to get obvious arches on but the color based returns make it pretty easy to ID game fish from the baitfish.
"According to the "sonar tutorial" Lowrance puts out, you have to be moving at a slow but steady speed relative to the fish, and have the fish go through the approximate center of your sonar cone.* The fish is at a greater distance from your transducer when it is at the edges of the cone, and closest when the fish is directly under the transducer.* It makes sense to me."***
Let's say the fish is perfectly suspended; not moving at all.* As you approach the fish the distance to it is further from the boat; this is the very start of the arch.* As you near the fish, it's distance from the boat decrease.* At the fish's nearest point to the boat, you get the top of the arch.* As you pass over the fish and continue on, the distance once again*gets greater; hence the 'perfect' arch.* This fish therefore would be stationary...not moving.* If the length of the arch were not of equal length...the fish would be moving.* If the arch, in fact were a straight line...you would have very active fish.* Probably feeding.* As you may be aware and 'arch' can be made in any part of the 'sonar cone'*making it very dificult to know where fish actually is relative to the boat (port/starboard).* Arch size is only relative to size of fish when all fish are directly adjacent each other,*someplace in the cone.* And the beat goes on...* *
__________________
Boston Whaler, "MUMBLER", 24 Outrage, twin 175 HP Evinrude Ocean Pros
Kind of makes you wonder why they show the arches if in reality it's seldom attainable. I guess we can thank the advertising and marketing guys on Wall St. for this. It does look nice in the ads. At least up until a few years ago most manufactures showed what you really see, a blop or pod. I guess the old saying, don't believe anything you hear and only half of what you see, still has merit.
Once you get past the thought that something's wrong with your FF, blob or arch who cares?* Either way, unless we start having neutrally bouyant rocks I'm going to assume it's a fish.
I do agree that this is*marginally false advertising, and causes a lot of needless concern.*
__________________ PAX River, MD
Fisheye
Channel 69
I have the RLC80 unit. To see arches you slow down the scroll speed. Not all the fish will show up like this but you will see some classic arches-try it out It really makes you feel good to see arches. The other thing I do is to adjust the gain down to say 75 % and the color gain, if you have color, way down so all the colors will show. This is how you can get a better idea of just what your looking at. Auto settings on my unit are recomended by Raymarine but I much rather tune it to get better info.
No Fish Arches 
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