Atmospheric Pressure
How often have you looked at the Atmospheric pressure before heading out fishing?
Barometric pressure can determine how high or low a fish lies in the water, along with their feeding habits and general mood.
As rain is forecast for the coming day’s, you can see the change in pressure today vs next Wednesday when the weather is to return to more settled conditions. See maps below.
There is a complex reason behind how the pressure works and how it changes the behavior of the fish. There are many different variations to how or even if it does have any effect on the fish. It’s the weight of the earth’s atmosphere causing pressure on the water’s surface and the pressure affects the fish is via their air bladder.
During weather patterns associated with high pressure (this is when the barometer is reading 1018hPa or higher), there is more pressure force on the air bladder causing it to be squeezed in and making the fish feel relaxed and comfortable. This brings with it good/normal fishing conditions.
During a low pressure (when the barometer is around 1014hPa or less), there is less pressure on the air bladder causing it to expand and therefore putting pressure on the stomach of the fish. This causes the fish to become uncomfortable and usually results in slow fishing conditions.
How the fish counteracts this drop in pressure is by swimming deeper in the water column. The deeper they swim, the more pressure is around them and the more comfortable they will feel. During the time of low pressure they will usually hide out on the very bottom of the waterway. It is more effective for an impoundment fish to swim deeper as they have depth beneath them. In rivers there is only so deep they can go which will cause the river fish to be less comfortable during low pressure and therefore harder to catch.
Please have a read on the link below and it will give you a little more detail on what i mean.
https://www.bcfishn.com/barometricpressure/
Jason