Air Pressure by Nic Brown

Air pressure explained & it’s effects on our quarry

One of the questions I am asked more than most is what effect pressure and weather has on Carp fishing.
Now to be fair this is an enormous subject and something that we could discuss, argue and debate for years, so I will out line the general rules and how it effects my thoughts and my approaches on any given day.

Please, if this is a bit basic for you then I apologize, but it confuses the hell out of a lot of people so I am simplifying it where possible.
What is pressure?
Air pressure is simple and ridiculously complicated all at once, simply it is the force exerted on everything by the particles in the air. Obviously we cannot see them but they still weigh something as well as taking up space. Because there are obviously gaps between all the molecules there is room for them to be squashed, this squashing is what is known as air pressure. The more compressed, the higher the pressure... Still with me?
Pressure is measured using a barometer. And is measured in "millibars" (mb). So when you look at Met Check and see that column you now have some idea what you are looking at!
Anything above about 1010mb is considered high pressure, anything below that, and especially below 1000mb means you need to move the earth to get on the bank, as your chances just took a strong turn for the good, especially if it is a low pressure front which is replacing a high pressure front. Have you ever been on the bank in mega heat, then it’s clouded over and started lashing it down, then almost straight away you have seen signs of active fish? This is the effect of a change to low pressure.
How does this effect my fishing?
Well this bit is probably the simplest part. The more pressure exerted on the surface of the planet, in our case the lake/river surface the less Oxygen is dissolved in the water, simply because the weight of pressure on the water takes away the room for gasses in the water, anyway, not important, the important bit is Higher the pressure, the less dissolved Oxygen there is in the water. The lower the oxygen levels the more lethargic the fish will be. Fish are simply natural beings, they eat to survive, to eat they must expel energy, to use energy they require more oxygen. So with little Oxygen in the water they don’t have the energy to feed much, which is why you won’t see them crashing about as much. Obviously though, more oxygen means more energy, more energy requires more fuel, that fuel is food! Meaning they should be more catchable.

Signs of Low & high pressure
So if you do not happen to have a Barometer or metcheck with you on the bank, what are the tell tell signs?
Obviously every rule has an exception, but when the weather is hot, still and clammy then the pressure is high, and in the winter if it is clear, still and freezing then the pressure is normally high. If you had a choice you wouldn’t be on the bank in these conditions. The only bonus though can be that the higher pressure often indicates the fish maybe higher in the water, as you know often on hot days the fish can be up for a mixer and sometimes even more so, in the winter they can be screaming for a Zig. Low pressure on the other hand (the pressure we want) is signified by over cast skies, winds and rain, so the conditions we would rather not be in are the ones that we should do our best to get out in!
A few years ago I was doing a fair few trips down to a Trout Lake that was only open during the summer months. The fishing was proving really hard with only a hand full of fish out so far and none to me in my 1st 5 over nighters, I had seen fish and had confidence in what I was doing, they just weren’t having it all.
The Lake was ideal as it had a toilet and you could drive anywhere round the bank, so I was able to take the misses. We were sitting at home one night in late August and the skies just erupted, from what had been a hot few weeks everything had just changed a quick look on met Check indicated a massive low front moving in, big SW winds, rain and storms. This was far too good an opportunity to miss, I convinced her it was a great idea (god knows how I managed that) and very quickly both us and the hounds were in the Surf on the way to the Lake, I already knew what area the wind would be hitting and as we pulled into the corner the waves were crashing into the little Jetty where my rods had been positioned quite a lot recently, but this looked different, this looked perfect. As I stood there getting battered I saw about 10 shows no more than 30 yards out, so I put three BIG Pva bags out into the waves, one at 30yards, one at 15yards and one literally 5 yards in front. My reasons for doing this were that I believed the fish would move further and further into this corner as the wind continued, long storey short I ended up with 14 fish that night with not one other nutter on the bank! In little over a month 19 fish had been caught, I had now had 14 of them in 12 hours.. A new pressure front really can be that important!
So I hope I have given you a little insight into the effects the air pressure can have on our fishing and how more often than not it will dictate how and where I fish.
Next time I will look at the effect different weathers actually have on my fishing, and although these changes are caused by the pressure, the effects are varied!

Till next time
Nic