Easy-to-understand barometric pressure and impact on fishing
Walleyes And Weather...
July 01, 2009
Todd Heitkamp still remembers the day his professor first explained the basics of barometric pressure in a Weather 101 class at the University of Wisconsin in Madison.
Barometric pressure is just the weight of the air, the prof said. It constantly pushes down on everything, like a big hand. It presses down on you, the earth and the surface of the water. He went on to say that stormy weather results from low pressure, when the 'hand of the atmosphere' pushes down with less strength. On the opposite end of the spectrum, clear blue skies come from high pressure, or a heavy hand, the teacher said.
Heitkamp instantly recognized how that analogy could help fishermen understand how fish behave. Most people use a barometer simply to help them guess as to whether they should take an umbrella with them. But, barometric pressure readings can also predict whether fish are likely to be biting, or if they will soon be biting- or, perhaps, if it's best to stay home.
Time on the water has confirmed the professor was speaking the truth, according to Heitkamp, who's been a meteorologist for the National Weather Service for the past 20 years.
"Weather is the most important influence on fishing," says Heitkamp. "In the tackle industry, I see all the latest gadgets and tackle. But what people haven't come up with is how to control the weather. If the weather doesn't cooperate, there's nothing you can do."
In simple terms, here's how Heitkamp sees it:
Barometric pressure- the weight of the air- decreases as a storm approaches. It's called low pressure. To understand how it works, imagine the palm of that giant hand the professor talked about easing up as it presses on the water's surface. Its touch is lighter. The water isn't as compressed as it was, and fish can move more easily through it. The mood of many fish often changes to what we might call a more 'active' mood. They move around more freely and feed.
A storm also brings clouds and wave-creating wind, reducing sunlight penetration. Active fish can move to shallower water. In the case of walleyes, they often rise in the water column. The sonar screen shows them moving up off the bottom. Or, they just move shallower on shoreline-connected and midlake structures.
Heitkamp believes that the absolute best fishing periods often occur when barometric pressure reaches its lowest point, just before the front arrives.
"The old saying, that fish bite best right before the storm," he says, "is true."
So, Heitkamp says, the best time to head to the lake is when the forecast calls for storms moving into the area.
The picture changes when the storm is over. Barometric pressure starts to rise again. The giant hand presses down harder, and the water becomes more compact. High pressure also brings clear, bluebird skies, and light penetration is often intense for the next several days. Fish feel the increased pressure and become less active. They move tight to cover or deeper, where the sun isn't so bright. Their mood is lethargic.
"With underwater cameras, you can watch fish come up to a bait and not bite it," observes Heitkamp. "People don't understand that, but when air pressure is high, fish become less aggressive. They just come up and look. They may eventually take it, but you have to work a little harder."
The effect of the pressure change is most pronounced on the first day after the storm passes.
Heitkamp said time of year must also be considered. The impact of a change in barometric pressure is more severe in winter. For one reason, the swing between high and low pressure is more drastic during the cold months. For another, the same high pressure is affecting less water volume when part of it is locked up as ice.
Heitkamp thinks fish like northern pike may be the least susceptible to changes in barometric pressure; they seem to be aggressive no matter what. But, the perch family, including walleye, may be the most impacted by the changes, followed by crappies and bluegills. Heitkamp doesn't target muskies often, but anyone who does will tell you the best time to be on the water is when black clouds appear on the horizon.
A barometer isn't needed to know what's happening with air pressure. Read the wind instead.
"Anyone can play amateur weather forecaster," says Heitkamp. "Before the (storm) front, wind is out of the south. When it switches to west-northwest, pressure begins to rise."
The old saying, "Wind from the east, fish bite the least," has a basis in fact, he added.
"Wind comes from the east the longer high pressure is in place," he says. "By then, high pressure has taken a real toll on the fish."
Test the professor. Make your own fishing predictions for a year by looking up the barometric pressure on weather websites. Then, keep a log and see how often you're right.
Heitkamp is a busy guy, like all of us. He must go fishing when he can, whether he thinks the weather will cooperate or not. Even when conditions are less than ideal, the barometer can help put more fish in the boat if you're willing to analyze the effect air pressure is having at that moment, he said.
"When you get out on a body of water, people do what they normally have done," theorizes Heitkamp. "We fish in a comfort zone. What they haven't done is check the weather. If you don't understand what the weather is doing, you're already behind the eight ball on learning what the fish are going to want that day."
Storm coming? Then low pressure is on its way, and faster, aggressive tactics may be best. For walleyes, trolling or casting crankbaits at shallow structures may be the keys. Look for schools cruising up off the bottom. Note the changes in depth as time passes. Keep the Beckman handy.
"When fish are aggressive," he says, "you can drop anything down there."
Heitkamp likes to use live bait anytime, so he tends to be a little more conservative even when the barometer points to the aggressive end of the scale. When the barometer is moving downward, he uses bottom-bouncers and Red Devil spinners. If he must slow down, he uses Lindy rigs.
He'll slow down even more as the grip of high pressure takes hold. Jigs are one tool of choice. He'll jig live bait on one rod to attract walleyes and use a dead-stick to get the bites. The approach works either in open water or through the ice. Because walleyes and other fish hold tight to cover, slip bobbers are another Heitkamp favorite.
You can't do anything about the weather. But, you can watch the barometer and predict where fish will be, how they'll behave and what tactics to use.
Weather, if you understand it, can help you choose where and how to fish.