Fish are sensitive creatures and understanding their sensitivities and reactions to them, is key to every angler’s fishing success.
We all know about how temperatures affect fish behavior, if it is too hot they go deep and feed slowly, if it is too cold they do the same, and we adapt our fishing tactics accordingly. But, what about barometric pressure?
Barometric pressure is another thing anglers need to consider when it comes to fish behavior and fishing success. But, it is often overlooked by anglers since understanding it and measuring it all is both complicated and time consuming.
In this article, I am going to run through the basics of barometric pressure, what it is, how it affects fish, fishing barometers, and how to use them for fishing so you can catch more fish than ever.
What Is Barometric Pressure?
Barometric pressure, also referred to as air pressure or atmospheric pressure, is essentially the weight of the Earth’s atmosphere pressing down upon every inch of the planet. It is created by the Earth’s gravitational pull, pulling down the air around it to hold the atmosphere in place.
Now, we can’t feel the weight of the atmosphere upon us as we are used to it but it is actually quite heavy, and a square-inch column of the atmosphere from the sea to the top weighs around 14.7 lbs. This is how much pressure we are under while we walk around at sea level.
How Is Barometric Pressure Measured?
Barometric pressure can be measured with a barometer and in a few different types of units. A barometer either uses atmospheres (atm), inches of mercury (inHg), Pascals (Pa), or bars (bar) (which is often used in diving) to measure the pressure.
A barometer should be seen as a barometric pressure weighing scale that simply increases its units during high-pressure systems and decreases its unit when low-pressure systems are coming or have arrived.
You will notice the barometer rising, falling, or staying the same which indicates the weather conditions to come, but also fish behavior.
How Does Barometric Pressure Affect Fishing?
Now that we understand what barometric pressure is, how it changes, and how to read a change, let’s have a look at the more interesting side of things, how barometric pressure affects fish.
Now, to fully understand how barometric pressure affects fish, we need to think about barometric pressure as affecting gravity in the water that the fish are living in. Since water is such a dense substance, the effect of gravity and pressure is greatly increased.
Pressure Changes Cause Food Depth Changes
When the barometric pressure drops, so does the effect of gravity on what is in the water as it is slightly lessened. This allows small particles in the water to rise up through the water column and this includes zooplankton and phytoplankton, which are the beginning of every food chain in the water.
When the zooplankton and phytoplankton rise to the surface, the smaller baitfish and anything else that feeds on them follows them to the surface too, and therefore so do the predators you intend on catching.
I have often seen bait balls of yellow-fin tuna on the surface and usually in cloud conditions and this is due to the plankton floating to the surface.
The same thing happens, except in reverse when you have a high-pressure system as the zooplankton and phytoplankton sink deeper and fish will follow the food depth down to this depth.
Fish Feel The Pressure Changes
Using their lateral lines and their swim bladders, fish can detect the slight changes in barometric pressure and their reactions to this change are closely related to what conditions the changes bring.
Pressure changes usually mean a change in the stability of the environment in the form of either adverse weather with low pressure or hot weather with lots of light in high-pressure conditions. This can affect visibility, water temperature, light conditions, and more, giving rise to uncertain times in the future.
This is why fish tend to “strap on the feed bag” during a pressure change as they want to eat as much as they can before the unknown, new conditions, arrive which might mean they can’t eat as well for a few days.
The fact that this survival requirement to feed coincides with the plankton movement we discussed above means that the fish have a ton of food to gorge on at a time when they want to eat a lot, and thus the fishing can be amazing when this happens.
You should also know that fish in shallow water feel changes in barometric pressure a lot more than fish in deep water. This means that a trout in a shallow river will change its behavior based on air pressure a lot more than a trout sitting at the bottom of a deep lake.
What Are The Best Barometric Conditions To Go Fishing?
Since fish do change their behaviors based on different barometric pressure conditions, let’s take a look and how they do so across each type of condition or change so you can use barometric conditions to your advantage.
Pressure is not the only criteria in determining the chances of catching fish, the length of time of the high or low-pressure period can be a factor.
As you can see, fishing during a change of barometric pressure is a highly desirable time to be on the water as the fish really do go for it. This is when you want to be fishing in an aggressive manner with active baits to match the activity of the fish.
That being said, another of the best times to be fishing is when the barometric pressure has been stable for 3 days or longer. This allows the fish to get into a good routine and find their preferred water level, oxygen content, amount of light, and more which causes them to feed more regularly and without worry.
In high-pressure systems, there is more weight on the water and therefore more gravity at play. This means smaller particles such as zooplankton and phytoplankton will be sitting a bit deeper and therefore the fish might be too.
High pressure also equals sunshine and warmth in most cases, and since most fish do not have eyelids, they will sit a bit deeper to avoid having the sun in their eyes. Also, the surface water temperature may increase too much for the fish’s comfort causing them to swim deeper and find a preferred water temperature.
Of course, this can have the opposite effect when the water has been too cold and needs warming up, like in springtime.
Low-pressure systems provide less gravity and therefore things like zooplankton and phytoplankton will be near the surface. It also means baitfish are likely to be there too and the predators you want to catch.
Low pressure can also mean cloudy weather and a cooling effect on the water temperature which can be a good or a bad thing. If you are trout fishing, clouds are great as fish sit deep to avoid direct sun in their eyes.
If it has been a hot summer and you suddenly get some rain and clouds, this can turn the fishing on, but it can have the reverse effect if the water temperature is already cold.
Barometric Chart For Best Time To Go Fishing
Where the fish are usually
Slow to medium
Mid depth or deeper water/near cover
29.7 to 30.4
At any depth
29.6 or lower
Fishing gets harder
Deeper water and near cover
Barometric Change Chart Impact On Fishing Chances
Fish are Slow and Innactive
Good, Normal Opportunities
The BEST Opportunities
There are quite a few fishing barometers on the market to choose from and some of them even indicate when the fishing will be poor, good, or great.
This fishing barometer does just that and it is worth having one of these in your fishing bag so you can start matching good and bad days to atmospheric pressure and its changes. You can also get electronic barometers in watches and GPS’ so you might already own one you can start using.
What Is The Best Barometer For Fishing?
Trac Outdoors Fishing Barometer – Our best portable Barometer Pick!
Make sure you review the options for the Suunto range as some do not have a barometer function. Look for the Suunto core, Sunnto 9 baro, and the Suunto 9 peak for the barometer choices.
It is a very durable watch and is water resistant to 30 meters. Other than the barometer function the storm alert and weather trend indicator is great for anglers.
Multiple features like a Storm Alarm, Altimeter, Barometer, and compass to monitor conditions while you do outside sports such as fishing.
The watch has a dual time function, a date display, and an alarm. The prediction time for sunrise and sunset will help anglers plan their fishing start and end times
Durable and full of features to use even when you are not fishing.
Suunto has 80 years of experience in watches, compasses, and dive products
Barometric Pressure FAQ
Is Barometric Pressure The Same Everywhere On Earth?
Everywhere at sea level will have the same barometric pressure so long as they have the same weather conditions. When you change altitudes and go higher, like when fishing on the rocky mountains, the barometric pressure reduces and you are under less weight since you are closer to the top.
What Causes The Barometric Pressure To Change?
The changes in barometric pressure come from a combination of changing winds, air temperatures, and the Earth’s rotation and these come together to create either high-pressure weather systems or low-pressure weather systems.
In a high-pressure weather system, it is usually warmer, the sky is clear, and the air presses close to the surface of the earth, increasing the barometric pressure.
In a low-pressure system, it is usually a colder, cloudy day with a chance of rain where the air isn’t pressed next to the earth as much, as it is held higher in the sky. This type of system has low barometric pressure.
This is how sailors use barometers to detect weather changes, as if the barometric pressure starts dropping quickly it is a sure sign of some cold bad weather coming in the form of a low-pressure system. If the barometric pressure goes up, it is a sign of good weather coming.
Thanks very much for reading my article. I hope you enjoyed it and now understand barometric pressure and how it affects fish and possibly your fishing success. Of course, it is not an exact science as other conditions play a role as well, but it is one you should keep your eye on.
Our best portable barometer the Trac Outdoors Fishing Barometer is a great buy for fishermen and is a very affordable option. If you don’t already own a watch specifically for outdoor sports use then go for the Suunto Core.
Steve is a seasoned angler whose lifelong passion for fishing has not only shaped his personal life but also laid the foundation for Positive Fishing—a community where he and his team of dedicated fishing enthusiasts share their love for the sport. With an impressive repertoire of skills honed over five decades, Steve has mastered both freshwater and saltwater fishing. Steve holds a special place in his heart for the mighty Carp and the elusive Tench