A combination of fisherman's fantasies and marketing hype seem to have people honestly believing that the fishfinder is the equivalent of some kind of underwater television camera. You just drive around until you bump into the fish and then catch them, simple as that, right?
What a laugh! As I've said before, we've even coined a term for the Fantasy Islanders who think this is the case. We call it being on the Magical Mystery Tour.
By "fishfinder" these days, most people are referring to a liquid crystal recorder with a scrolling screen. In theory, these should be able to show any fish that are under the boat. Now let's be clear, I know that with multi-thousand dollar units on big-water boats operating in depths of 100 to 2000 feet of water you CAN in fact see shoals of fish. That's not what we're talking about here.
So back in RealityLand where we fish in depths of >50 feet . . . I've used these things since they first came out as "flashers" in the 1970s and continued all the way to today's LCR units and you still can't reliably use them to "spot" fish. It doesn't work that way and here's why.
1. Is it really a fish? There's no way to know, but I suspect in many, many cases the "fish" you are seeing on the screen are not really fish at all. I've never been convinced. How accurate are they in real use? It's anyone's guess.
2. Time lag and 2D vs 3D - Depending on a long list of variables, what you "see" on the screen can be anywhere from directly under the boat to 25 or more feet behind you because of the time lag it takes for the unit to "draw" the screen. The depth is generally accurate, but because of the way the scrolling works to draw and redraw the screen it's very difficult to know where, exactly, something that's on screen would be located.
Also, the fishfinder shows the underwater world in 2 dimensions so to precisely know where those "fish" were that you "saw" such that you could accurately cast to them, you'd have to know all 3 dimensions to the accuracy of a couple of feet. The fishfinder doesn't tell you any of this accurately.
3. Field of view - I don't pretend to be an expert in this, but from what I've been told the sonar beam is essentially an inverted cone. The diameter of this cone depends on the depth of the water. In fairly shallow water, the "cone" may be only a few feet wide. I've heard/read that this principle has changed somewhat, but this all goes back to the question of knowing where the alleged fish really are.
4. Fish aren't stupid. Does anyone believe you can really drive a boat over the top of fish and they'll just hang out down there as if nothing happened?
I currently have 3 LCR units of various makes and they work great. For showing the depth and the approximate contours of the bottom. That's it. Sorry to burst your bubble.
The only thing I believe they reliably "find" is structure that might (might, might) hold fish. But that's combining what the fishfinder tells me with my experience or more often than not, my guesswork, so it's as much me finding the fish as it is the "fishfinder".
These units are great for a number of other reasons, the main one is safety. I run rivers in my boats and at 25 or 30 MPH, it's nice to know how much water is under the hull before you find out the hard way there isn't enough. There are no accurate depth charts for rivers, and I've been amazed at the times I've been running 100 yards or more from shore and suddenly the warning goes off that I'm in 3 feet of water. Or less.
But as far as finding actual catchable fish, forget it. Sorry, but we caught a lot more fish back before everyone spent their fishing time staring at the video screen. Whether or not you believe what the fishfinder tells you, it still is all you when it comes to catching it.
Grouse
Fish finders
but hey thats just my opinion.
Linear Mode
