This pressure, measured by weathermen in hundreds of an inch and displayed on weather maps in isobars, is behind all weather changes. Now, we all know that weather affects fishing, but many fishermen don’t realize how much atmospheric pressures directly influence the behavior of shallow fish. (The deeper the fish the less they are affected.)
It is a bit complicated, and a little hard to explain, but the scientific reason that barometric fluctuations affect fish has to do with the pressure it exerts upon their swim bladders. This air sack is to a fish what the inner ear is to a human. It controls their equilibrium.
To put it simply, when this sack gets out of wack, it makes them feel a bit wobbly and unsure of themselves, so they are less likely to chase things.
The most common excuse for not catching fish during the spring is the passage of a cold front, but it’s not the temperature so much as it is the change in atmospheric pressure that has an immediate and dramatic influence upon fish. Water temperatures change slowly and gradually, but pressure changes are instantaneous.
A lot of people believe that fish spend a lot of time moving from shallow to deep and vice versa, but, because water pressure also affects the pressure exerted upon their swim bladders, this isn’t true. They do migrate between shallow and deep, but this is a gradual movement that takes days or weeks. Repeated or rapid depth changes would knock them silly. Rather, I believe there are fish acclimated to deep water and those acclimated to shallow water all through the regular fishing season.
Because sever fluctuations in barometric pressure changes the aggressiveness of fish that happen to be shallow more than those that happen to be deep, the bite changes from a shallow bite to a deep bite.
I kept close tabs on the barometer for a couple of years back when I fished every day of spring, summer and fall. The key for most situations is usually not how much the barometer has fluctuated during the past hour or two, but during the past 24 hours or more. To keep track of that, you’ve got to keep notes.
The best pressure of all, at least for numbers of fish, is a barometer that is steady for three days. This is rare, especially during the spring. The next best thing (and the best for really big fish) is a rapidly falling barometer, which is what you get just before a front. Some, not all, of the very best catches I’ve made were when I was looking over my shoulder every few minutes, wondering if I should make a run for it. I got wet a bunch of times, too. This is true not only for bass, but for all species, because they all have swim bladders. Any experienced cat fishermen will tell you that the catfish bite best just before a storm, too.
Next best is a slowly falling pressure. Next is a slowly rising barometer. And worst of all is a rapidly rising barometer, which is what you get after a frontal boundary passes.
When the weather clears and the sun comes out (when it looks like a great day to go fishing)This is true not only for bass, but for all species, because they all have swim bladders. Any experienced cat fishermen will tell you that the catfish bite best just before a storm, too., shallow fish move into the shade, or a little tighter to cover because of the way their eyes work, but how active they will be is determined mostly by the barometric pressure. When the barometer knocks them for a loop, you’ve got to put your baits right in front of them and make it easy for them to eat.
That’s why flipping, I believe, has become so popular and productive. Flipping works best on what I call "frontalized" fish. For those of us who don’t like flipping, of which I’m one, the best way to approach frontalized fish is with a much slower presentation and more finesse. Sometimes downsizing helps, too.
Most of us think the best times to go fishing is on "pretty" days, which, unless it has been pretty (and the pressure has been fairly constant) for three days straight, are really the worst times to go fishing. What feels best to us up here in the air often is the opposite of what feels best to fish down there in the water.
I realize all this probably raises some questions, but there is not enough room here to explain it all. Besides, I really don’t know it all.
What I do know, is that the barometer is the bottom line–and it behooves fishermen to think beyond the obvious weather conditions to the forces behind the scenes that actually create them, and to how these same forces drastically affect the mood swings of shallow fish.
Scan 1 of 2: Watching the movement of the barometer can indicate who and what you should fish. Photo by Ron Kruger
Scan 2 of 2: Spinnerbaits are a favorite spring bait, but when fish have been "frontalized," they won't chase fast-moving lures. Photo by Ron Kruger.