Most people know that weather can affect fishing. Depending on the season, warm and cold fronts can heat or cool the water and encourage or suppress feeding behavior.
A warm front in spring can bring the water temperature up, and the sun can also help. This heat can turn fish on, while it lasts. However, a warm front in the high-seas can increase the water temperature so much that fish become stressed and won’t eat.
Experienced anglers are well-aware of the importance of monitoring atmospheric pressure (also known as barometric pressure) which can have a dramatic impact on their fishing.
What is barometric pressure? What does it do to fish? How does it affect fish?
Are you looking for answers? Continue reading!
Barometric Pressure: The Essentials
Barometric pressure measures the mass of the air column above you. Everything with mass attracts to the earth’s gravity, including oxygen, nitrogen, and carbon dioxide as well as other gases that make up our atmosphere.
The atmospheric pressure is affected by the mass of the air column above you. If you have ever felt your ears pop when driving down a mountain with your car, or when you descend from high altitudes on a plane, this is a real phenomenon.
The United States measures barometric pressure in inches of mercury (inHg). Scientists and meteorologists can measure the pressure that the atmosphere exerts upon a column of mercury to determine this important weather indicator.
Stephen Baig, an oceanographer at The National Oceanic and Atmospheric Administration explains that “Imagine a U-shaped tub… At one end, liquid mercury and the other is open to the atmosphere.” The mercury rises when the air pressure is higher. The mercury level drops when the air pressure falls.”
Under normal conditions, the mercury rises to 29.9212 inches at sea level. Anything above that number is high and anything below it is low.
High barometric pressures are associated with clear, sunny skies. Low barometric pressures indicate the approaching of cold fronts and storms. Hurricanes and other severe storms are often associated with very low pressures.
According to Sciencing “If the barometric pressure changes rapidly, it is when the pressure increases or decreases by more than 0.18 inches per hour.” A rapid change in barometric pressure of less than 0.003 to 0.04 inches in three hours is considered slow. An increase of fewer than 0.003 inches in three hours is considered steady.
What Does Barometric Pressure Have to Do with Fish?
Do three main ways do barometric pressure impact fish?
Lateral lines –The lateral line runs the length and width of fish’s bodies. It is a long, sensitive organ. It detects vibrations in the water and alerts them to injured fish or other food sources. This lateral line is what fluttering, vibrating, and rattling lures attract hungry fish.
The sensitive lateral line can sense even small changes in atmospheric pressure. This is because the pressure against their bodies changes with the increase in air weight above water.
Fish are a natural barometer that measures atmospheric changes.
Swim bladders –Bony fish such as largemouth bass, pike, and redfish have an air-filled bag in their abdomens. They use this swim bladder to regulate their buoyancy. As the pressure on the fishes’ swimming bladders changes, it can cause discomfort and force them to adjust.
Fish may feel pain when pressure rises rapidly, just as it can for your ears to adjust to increased pressure.
Spud Woodward is the Assistant Director of the Georgia Department of Natural Resources Coastal Resources Division. He says that fish with small air bladders (such as Spanish mackerel and kings) aren’t affected as much by barometric changes as those with larger bladders like trout, redfish, and tarpon.
Ralph Manns, a fishery science expert who studied the effects of barometric pressure in Texas on bass, warns that sensitive fish can adjust by simply moving a few inches lower or higher in the water column.
Plankton and other small food sources are –The barometric pressure directly influences the water pressure at depth. As it changes, small food items such as plankton are moved in the water column. These pressure-induced migrations can cause fish to move as well. This can lead to some species like crappie moving higher up in the water column, while others may be sent back down into the depths. This can encourage or discourage feeding. This will also have an impact on many prey species.
What Does Barometric Pressure Have to Do with Fishing?
Here is where things start to get confusing.
Manns is skeptical of scientists like Manns. “We observed no obvious relationship between pressure readings or the nature of pressure changes and the behavior of largemouth and Guadalupe bass in Lake Travis, Texas… when the possibility that air pressure alone controls fish behavior is considered,–distinct limitations appear.”
This doesn’t necessarily mean that barometric pressure has no impact. However, it can’t be separated from weather changes, precipitation, and wind cycles.
He concludes that “we await any scientific interpretation or information that better explains how gamefish behavior is related to changes in air pressure.” This explanation can be separated from the confusing effects of weather conditions. We believe it is more plausible and likely to be more accurate to take into account weather and sky conditions for fish activity and inactivity to be explained until a biologically acceptable mechanism is developed.
What does this mean for you?
Barometric pressure readings indicate weather patterns. The complex associations between pressure and sunlight, wind, rain, precipitation, and humidity appear to have an impact on fish behavior, though we aren’t sure what they mean.
However, the long-term experience of anglers can help us to get a sense of how atmospheric pressure affects fishing.
What are the best times to fish?
48-72 Hours of Steady High Pressure (>30.5 in-Hg).
Clear, sunny skies are a great combination for days of high pressure, which makes it great to get out on the water.
This is good news because fish and prey items are more likely to be found in high-pressure areas and feed continuously. After a high-pressure system has settled in, expect vigorous feeding for 48 to 72 hours. Fishing will continue to heat up until a new system is established.
Rapidly falling pressure (>.18 in-Hg difference in 3 hours)
This is the best time to fish in barometric conditions.
Fish can sense a pressure drop and will feed hard as they wait in deeper water.
Anglers who are savvy know that a falling barometer is a sign to get in the water, and they do so with fervor!
Terry Sullivan is a New Jersey charter captain who is well-versed in this pattern. He says that striped bass has been seen feeding on wild food right before the barometer dropped. “During summer we experience an upwelling effect before a front. It triggers a local hot bite right before the southeast wind shifts southward and starts to blow. This is just before the front. Fish sense a shift in the weather and feed heavily just before it happens. They shut down when the wind blows hard south. They know that they won’t be able to eat for several days so they have to gorge.
Is it just atmospheric pressure? It’s not, but I would take it seriously!
Manns believes there is something to it. “…Frontal passages, as well as the associated conditions (overcast skies, wind, rain, and temperature changes) often seem to turn on bass. It seems that bass activity was affected by low-light conditions and heavy cloud cover, rather than air pressure changes.
We would love to have a scientifically backed answer, but this is not the case.
We know that barometric pressure, and the associated weather changes, affect fish behavior. But we aren’t sure what the mechanisms are. We can confirm that fish are attracted to both high and low pressure, as evidenced by professional anglers and scientists.
Please leave a comment below if you have any questions or suggestions. We would love to hear from you!