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RM fishfinder questions

Old 06-08-2009, 04:08 PM
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jwb
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Default RM fishfinder questions

I have a C120 with a DSM300. I want to know if there is any way to adjust to show fish better (symbols??) I looked and found "gain" with hi , med, and lo. Maybe I am missing something. My concern is I am always showing "stuff" in the water and not sure if it is fish, weeds, jimmy hoffa or what. Any help would be appreciated. It shows the bottom well but it is the suspended stuff I wonder about. If there are schools of bait or if there are stripers near the bottom what exactly will I see and how do I differentiate from seaweed, etc.?
Old 06-08-2009, 04:48 PM
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It doesn't matter if your display shows the picture of a little fishy or an arch......The sonar is just telling you that there is something suspended off of the bottom under your boat.....The machine has no way of knowing whether it is Jimmy Hoffa or a 200 pound Mako! Leave your machine in auto mode until you get more familiar with it. That model is actually very good in auto......Basically bait will show up in large odd shaped blobs sometimes from top to bottom and sometimes just in certain depths. The solid small returns often around the bait are usually game fish. depending what you are looking for..........Striped Bass usually near the bottom.....Tuna and Shark from the surface down to hundreds of feet! Flounder and Halibut.......Pretty much forget seeing them because they are usually sitting on the bottom. Use you machine more for finding structure like rocks and ledges, and wrecks and then you will find your intended quarry. IE.....You will often mark a wreck say 20 feet off the bottom, as you drift over the wreck you will often see bait balls and predators right on top of the wreck but you can catch fish as you drift off of the wreck without seeing them on the screen.......Your machine has a great split screen function that shows the full depth and then an expanded view of the bottom section of the water column at the same time...... Once you get familiar with everything I said, then play with the manual modes of the machine but it really isn't necessary.
Old 06-08-2009, 05:02 PM
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Actually, fishfinders do "know" what it is they're sounding. Modern fishfinders mark fish by detecting their swim bladders.

You should find a section very similar to this in your Ray manual:

7.4 How can I enhance what I see?
You can enhance the image by applying the following options:
• Change the range (Range).
• Shift the selected viewing range (Range Shift).
• View a zoomed area (Zoom).
• Flatten the bottom image to help separate fish from the bottom (Bottom Lock)
• Isolate bottom fish (White Line/Bottom Fill)
• Pause the scrolling image or adjust the rate at which the image scrolls (Scroll Pause/Scroll Speed)
• Change the size of or remove the depth digit.

Old 06-09-2009, 05:04 PM
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I had the same issue as I have an E120 with a DSM 300. I was concerned due to not seeing any fish arches so I called and talked to a technician at Airmar and Gemeco who both told me the same information. A lot what you see or do not see has to do with the quality of the transducer, frequency of the transducer along with the cone angle. The output wattage of your unit has more to do with depth capabilities than resolution under 500'. If you have a transducer with a narrow cone angle (under 20 degrees) running at 50KHZ you will get a lot of targets do not have seperation or much definition (unless its a broadband transducer). A narrow cone angle (under 20 degrees) at 200KHZ gets great target resolution and seperation but will usually not show an arch. If you widen the cone angle to greater than 20 degrees at 50KHZ to 200KHZ you will begin to show fish arches due to the fish being in the cone angle for a longer period of time. I had a Lowrance that showed excellent fish arches but it also had a 20 degree 200KHZ transducer. I show fish arches running my E120 at 50KHZ due to the wider cone angle at 45 Degrees but do not show any at 200KHZ at 12 degrees. Also try zooming in on the target when you are running in water deeper than 400' due to pixel resolution at deeper depths.
So basically what they were telling me do not worry about your unit not showing fish arches. The more time you spend out on the water and comparing what you see on the sounder compared to what you are catching, you will soon be able to figure out what fish species you are picking up with your sounder. The Raymarine units work pretty well in auto mode but once you have been at it for a while you can learn to fine tune those units to get awesom detail.
If you go to the airmar website they have a lot of information on transducers and how to get the most out of them.
I hope this info helps you in detremining your problem.
Old 06-10-2009, 08:18 AM
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Davepenn is right. What you should be looking for is the size of their swim bladders. I admit, it takes a little getting use to, but once you figure it out it is awesome. My first trip this year with my C80 with DSM 300 we went looking for cod. We kept marking thin lines at around 35-60 ft. Turned out to be herring and makerel we were in 300 ft of water. We moved in a little shallower (250ft of water) and found a big school of cod. You could clearly see the swim bladders. They show up as red dots surounded by yellow. The bigger the fish the bigger the bladder, the bigger the red part. We dropped the jigs (watched the jigs go to the bottom, really!) and proceeded to hook up. It was unbelievable. I guess every manufacturer is a little different on how they present it to you. Just becuase its an arch or fish symbol, doesnt mean its a fish.

I also find the auto gain to work perfectly so I dont mess with it.

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