reading fishfinder marks

[steve dover]

does anyone know of a site or source of info that provides interpretation of fishfinder readings or marks? I would like to learn more about how certain baitfish and targetted fish show up on sonar. I frequently struggle to figure out are those marks sheephead, perch, whitebass, whitefish etc or walleye; and are those marks baitfish and if so what kind. I realize there are no magical answers but i am interested in any sources for speeding up the learning process as i feel like i should be better at interpretting my sonar after roughly a Zillion hours on the water with top of line electronics. too often my main fishing partner and i are looking at the screen saying what do you think THAT is? that's part of the fun of the whole thing but any help appreciated. thankx....

[SUPERTROLLER]

I've come to find that most of the time when I'm marking lots and lots of fish and not catching many of them, that these are the walleye. When I'm marking good numbers and catching sheephead, catfish, carp, and perch; I'm usually over a lot of sheephead, catfish, carp, and perch.

There are really only 2 things you can do.
1) Catch whatever is under the boat to see what it is you're marking.
2) Drop a camera down to see what under your boat.

There is no way to differentiate between individual fish on your graph. You CAN tell when a school of baitfish is under your boat but not necessarily whether they are shad or alewives or shiners or smelt.

[fishy]

No offense, but with all that experience with fish finders, I’m surprised you’d think a fish arch would appear noticeably different from one freshwater species to another (other than big arch = big fish, little arch = little fish). All you can do with today’s technology is to go fishing and learn as much as you can about the tendencies of certain species to appear in certain places at certain times on a certain body of water. Unless of course you invest in a good underwater camera.

[Sunshine]

I humbly disagree to an extent. After spending hundreds of hours staring at the graph while open water trolling I feel that I can accurately distinguish between sheepshead and walleye. I'm curious if others have determined the difference.

Size of arcs on both length and width can give you an indication also. Ever see the extra dots on the belly of an arc and know that it's different from the rest? Ever figure out what they were?

How about seeing what looks like blobs on the screen while trolling? What are those?

Let's not jump all over this guy and his question too soon. He may have some good insights.

Before my sanity is questioned too much, I'm only talking about trolling open water.

What do others think?

[manitobawalleye]

have also read that the lindsay brother's
who have won the kbi and rainy lake bass tourneys distinguish between smallies and walleye's....
this was in a in-fish mag a few years ago...
they were at the time running x-85's

[Hogslammer]

Try this http://66.216.66.212/forum/showthrea...7&pagenumber=1

[dlhomes]

Learned the difference between walleyes and carp on X-85 with the help of aquavu. Always walleyes in w/the carp. Also can get good idea on what a wlleye mark looks like. Also noticed x85 did not mark eyes if less than 1-1.5 ft off bottom!!

Just thought I'd point out that the size of the arc is not always a reliable indicator of the size of the fish. Where the fish is located in relation to the transducer cone will affect the arc (in the center of the cone vs. off to the side), as well as will the size of the fish.

Right, the length of the arc does NOT show the length of the fish. It shows how much time the fish was in the "cone" area that the transducer is reading. Notice at anchor over top of a fish, the fishfinder will show a line indicating the depth the fish. This line might go all the way across the screen. The Thickness and shading (if applicable) will indicate the general size. You might also go to www.Lowrance.com and look at the tutorials. They show several pictures for each model of graph, and definitions for each.

[Jim Ordway]

Hogslammer,
Great post. I think the only answer is to run a camera to determine what the marks represent. According to the Vexilar website, the fish body has much the same water content as the surrounding area, and, if fact, the reading you get is actually from the size of the fish air sac. It seems counterintuitive, but I guess were all still learning out here. The logic of the post you have shown seems to make sense. Now to sort out who knows what..
Take care,