OK

OK, I just read another forum post where someone mentioned seeing fish "come up from the bottom and look at his downriggers" on his fish finder. Well, the trolling camera's will show fish swimming up from behind, and maybe some do "come up" from deeper water, but it is my belief that this is VERY RARE.

Salmon like two things, food and temperature. They find food at a depth and they can adjust to the temperature, but it takes a lot to get them to change. That is why a difference in 5 feet on a rigger or a dipsy will trigger strikes.

Salmon Fishing 101 - What is my fish finder telling me?

The fish finder is telling you the distance from the transducer to the fish.

Repeat this until you get it. As you approach a fish, he will be, say 85 feet from your transducer. If you cruise directly over him, you may see his true depth is 70 feet down. As you move away, you will show the distance increasing. This appears as an upside down U shape. It does not mean he was 85 feet down, swam up and then swam back down. It does not mean it was anywhere near your downrigger ball. You may be overtaking him, he might be overtaking you, he might be swimming in from the side, YOU DO NOT KNOW.

Most marks will be short, if the fish is not within the "cone" of your fish finder very long, swimming in any direction but the exact same one as you. A long mark like this means the fish is probably swimming in about the same direction as you, and is probably a very good sign.

Also, the top of the mark is not necessarily the fish's depth, unless you go directly over it. So seeing several fish at a depth ranging from 50-60 feet deep tells you they are most likely all slightly shallower than 50 feet.

This effect is greater the deeper you go, as the "cone" of your transducer's range increases in diameter.

Same thing goes for your downrigger balls. The out down rigger on the far side of your boat is 20 feet down, and it is 10 feet away from the transducer, it will read as 23 feet from the transducer. This effect DECREASES the deeper you go, as the angle between the transducer and the ball decreases. At 100 feet down the ball will show as 100.4 feet.

This is not to say that you should not keep a close eye on the 50 foot rigger when you see that mark "coming up to it", it could be a fish coming from somewhere toward that rig to nail it. Just don't think you are looking at a television picture there.

Part 2 - I just marked a 28 Pounder!

The fish finder sees the fish "bladder", the air bag fish use to keep at a depth. Big Mark=Big Bladder, NOT Big Fish, necessarily. At the same depth/temp, the bigger bladder should belong to the bigger fish, but a fish in warmer water will have a bigger bladder. Cold water is more dense, so that Master Angler Award fish just below the thermo cline might be the smallest mark on the screen.

Understand what the fish finder is REALLY telling you and you will be a better fisherman and catch more fish.