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Old 07-25-2004, 10:40 PM
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Default Barometric Pressure and How it Affects bass / ? The Pressure Myth

By Bill Dance

I honestly believe that the main reason largemouth bass are such a challenging gamefish is because they seem to be more influenced by environmental changes than other species. Nearly everything that happens in the air and in the water has an effect on most freshwater gamefish, especially largemouth bass. Normally two, or more fluctuating conditions are in effect at the same time - simply because they are all related - and everything that happens in the atmosphere eventually affects the watery world of fish. In all my years of fishing, one of the key things I've noticed (particularly about shallow water fishing) is the dramatic influence that barometric pressure has on fish. Ironically, this is the one influence that biologists, ichthyologists and serious fishermen have studied least. This could be because the required equipment is so delicate that it is difficult to take to the lake. And the whole pressure equation really gets complicated when you try to measure it against water pressure which also changes as fish change depth. It is a well-known fact that even minor barometric pressure changes affect a fish's swim bladder. This air-filled sac is to a fish what the inner ear is to humans. When the barometric pressure rises quickly, it exerts pressure upon the bladder, thus affecting the fishes equilibrium making it hard for the bass to maintain perfect balance. Naturally, this affects their behavior and appetite. I'm sure you've heard the term barometric pressure many, many times, but do you know what it actually means? Simply stated, it is the pressure of the atmosphere at a given point and time. And it's measured by a barometer, which is an instrument for determining the pressure of the atmosphere and predicting probable weather changes.
About 10 years ago, I started watching the barometer very closely. I had a cheap version that worked fairly well, but just to be sure, I would also check with the local weather service before and after every trip. This improved my understanding of how pressure fluctuations affect bass behavior. All serious bass fishermen know that the barometric pressure has a dramatic and immediate effect on a fish's personality and mood. Without question, it is an important element that influences fish behavior, especially shallow-water bass. Deep-water fish are not affected as much by major pressure changes and this is why they are more dependable on those days. Something to keep in mind is that barometric pressure doesn't change dramatically during a period of just a few hours unless a major storm is moving your way.
Like fish, other wildlife can predict the weather better than The Weather Channel or the National Weather Service. Mother Nature has given her creatures the uncanny ability to accurately anticipate an approaching weather system as well as knowing how long it will last. As a general rule, I concentrate my efforts in shallower water during falling pressure and in deeper water when it rises. Normally, barometric fluctuations are most important during late fall, winter, and early to mid-spring (because that is when fronts that frequently move from both the northwest and due north are strongest). Fronts that occur during the summer and early fall seem to move more from the southwest or west, and have less effect. Plus the recovery time is much quicker during these warmer periods of the year. A lot of folks think that the perfect day to be fishing is a beautiful day, when the sun is out, the sky is blue, and there's not a cloud to spoil the view. But let me tell you, most of the time these are the worst conditions for catching fish, because these conditions normally prevail just after a front has passed through. This is the type day when the pressure goes up and up - and the fish either go down or move into thick cover and seem to get lockjaw. When these conditions occur, you have to really slow down and use lures that you can work extremely slow (those that appear less likely to escape). Worms, grubs, or jig-and-pork combinations are good choices.
How many times have you heard fishermen say Wind out of the east, fish bite the least. Wind out of the west, fish bite the best. Or Wind out of the north, don't venture forth. And Winds out of the south, blows the bait in the fish's mouth. Well, first of all, the direction of the wind doesn't directly affect fishing. I've caught fish in wind of all directions except when it was blowing so hard I couldn't get out, or perhaps when it was too strong to fish a particular area. However, there is some truth about the effects of wind direction which actually has its roots in the barometric pressure. That's right, it deals with fronts. A strong brisk north or east wind will generally indicate a fast weather change; therefore, a drastic change in barometric pressure. Gusty south or west winds usually indicate a slow changing weather condition; thus minor changes in the pressure. So it's not really that the wind affects fish behavior. Instead, it's the barometric pressure that affects the wind and, therefore, fish behavior.
I think it would be safe to say that most fishermen can remember times when they were really whacking the fish and all of a sudden the wind changed direction and the fish stopped biting. This happens often, but again, it's not actually the wind that makes the difference. A dramatic shift in wind direction is the result of a frontal passage or change in barometric pressure. If I've said this once, I've said it a thousand times: the best time to go fishing is any time you can go. But if you can schedule your trips to coincide with the best weather forecast for current conditions, it will certainly pay you to do so because this is when the fish will be the most active.
Let me take a minute to explain what my experience has been with different ranges of pressure both the good and the bad. Where I live in west Tennessee, our normal pressure is 30 inches of mercury. So naturally, any reading below 30 is low and any above 30 is high. An optimum range would be 29.98 to 30.02. Without question, some of my best catches and biggest fish have come from mid-spring to early fall after several days of normal pressure were interrupted by an approaching front that caused the pressure to fall extremely fast (more than 10 to 15 points) in a few hours time. Normally during such a period, you will see bad weather moving your way, and the bass will go on a feeding frenzy. Unfortunately, these feeding sprees are short lived and to take maximum advantage of them you have to take the unsafe risk of possible high winds and lightning.
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