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Rising water temps

These are purely my observations and I place only enough credence in it to follow the theory myself defiantly not to encourage others I believe fish have some sort of sixth sense for predicting the weather, we don’t but the air temp is our nearest indicator of what will happen in fairly short order. So what, fish are cold-blooded; their digestion rate is set by the temperature. Another thing that affects their metabolism is the dissolved oxygen levels. Henry's law states that pressure and temperature are the controlling factors on levels of dissolved gases in water. Changes of levels of dissolved oxygen in water are fairly dramatic as water will more readily dissolve oxygen than nitrogen. I cannot remember the exact percentage in water I think something around 35% oxygen to nitrogen. In air we breathe 20.9% oxygen to nitrogen. Therefore a slight rise or fall on the barometer has a large impact on how much oxygen a fish has to apportion to its digestive system. Fish do not feed well in sustained long cold spells; I do agree some fare better than others. They do however break their fasts before we have taken the thermal vests off.
 
I`d say today would be very good for Barbel from most rivers, and am sure the water temps have risen enough for some catch reports later today! And hopefully some members will post some up-to-date river temps, can`t wait to get out myself either!! :)
 
About the only temp I can say for definite is rising is mine as I'm loaded with flu and am now talking like I've spent the last week gargling with napalm. Get out there and give it a whirl, looks a cracking day to be on the bank and if you catch, well that's a bonus.
 
Shaun Nurse said:
I`d say today would be very good for Barbel from most rivers, and am sure the water temps have risen enough for some catch reports later today! And hopefully some members will post some up-to-date river temps, can`t wait to get out myself either!! :)
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Well two of us failed to register a touch on the Severn today, didn't take any temp readings but the the water was still ice cold, reckon it needs a bit longer to warm up.
 
Sam Lloyd said:
Oh yes it is :);)
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Stolen from wiki:
The low compressibility of non-gases, and of water in particular, leads to their often being assumed as incompressible. The low compressibility of water means that even in the deep oceans at 4 km depth, where pressures are 40 MPa, there is only a 1.8% decrease in volume
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Jim Foxall said:
If, Sam, you are talking about water in the vapour phase, (gas) then, yes, it is compressible. To all intents and purposes, liquids are not. That's why liquids are used in hydraulic systems.
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Jim as Darryl has quoted from wiki they are compressable. Infact in very high pressure hydraulic systems you do have to take it into account. Especially where precision is required... Also its how some pressure vessles are checked for structural soundness. You pump water in and compress it to get fantastic levels of stress in the material. First year at Uni stuff its stressed to students that liquids are compressable and its a common misconception that it is not releveant the amount they do compress.
 
I wonder how much the air pressure influences oxygen being disolved in water? As pressure increases would it be "driven" more easily into water?
 
This is like being sat at the worst possible dinner party. I have you lot to my left and on my right, Nick Clegg, Hitler, and Peter Andre. But it's mainly because I have no chuffing idea what you are talking about and Peter Andre keeps "singing" because he feels anxious.

The key question for me in all this is, can I go fishing tomorrow or not?
 
Howard Cooke said:
This is like being sat at the worst possible dinner party. I have you lot to my left and on my right, Nick Clegg, Hitler, and Peter Andre. But it's mainly because I have no chuffing idea what you are talking about and Peter Andre keeps "singing" because he feels anxious.

The key question for me in all this is, can I go fishing tomorrow or not?
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If i had Peter Andre sat next to me singing i'd be going today! :eek:

Sam Lloyd said:
I wonder how much the air pressure influences oxygen being disolved in water? As pressure increases would it be "driven" more easily into water?
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Yes - but i think temperature is more important than dissolved oxygen levels. Low pressure systems often bring warm rain - like we have at the moment. Since an increase in temperature and a drop in air pressure results in lower dissolved oxygen levels you could assume it would be a bad time to go fishing if oxygen levels were the deciding factor. In reality we know it to be a good time to go - fish are cold blooded so an influx of warm water will result in increased activity regardless of the affect on oxygen levels at this time of year.
 
Total pressure =( depth x density of fluid x gravity) + atmospheric pressure. So as you can see atomospheric pressure dirrectly affects the water pressure. The deeper you get, the more negliable it will become. However as we're talking about very small depths maybe it is important ?? At 10 meters the atomospheric pressure will account for half of the total pressure.
 
This is like a science lesson. One of the best sessions I have had in recent seasons was when I had to scrape the ice off my windscreen and go fishing in the snow. If you're on the bank you have a chance of catching.

Maybe I just get lucky in 'unfavourable' conditions :)

If I analysed temps to this degree I would never get out fishing. I don't even own a thermometer and the day I do is probably the day I should take up another hobby!

Maybe Andy should stock science lab jackets in the BFW shop?
 
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Sam Lloyd said:
Jim as Darryl has quoted from wiki they are compressable. Infact in very high pressure hydraulic systems you do have to take it into account. Especially where precision is required... Also its how some pressure vessles are checked for structural soundness. You pump water in and compress it to get fantastic levels of stress in the material. First year at Uni stuff its stressed to students that liquids are compressable and its a common misconception that it is not releveant the amount they do compress.
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The reason that you can transmit pressure by a liquid IS because liquids are not compressible. If you push the break pedal of your the car the pedal does not feel spongy because the hydraulic fluid transmits the pressure you apply by your foot to the brake. The liquid does not compress. If you carry out a pressure test on a cylinder, you fill up the cylinder. You then increase the pressure on the surface of the water in the cylinder. This pressure is then transmitted to the internal surfaces of the cylinder precisely because the liquid is not compressible. Liquids are about as compressible as a solid!

If we are talking of pressure in water, then there are two components, the pressure due to the weight of the water + atmospheric pressure. It is pretty common knowledge that the deeper a submarine dives the greater the pressure on the structure. I would have thought that the difference of a few millibar at the surface, would be of no consequence in water. Food for thought
 
"...be prepared to explain in great detail why you didn't catch fish, being careful to lay it on something that no one else was paying attention to, like the ozone content of the air or electromagnetic interference from satellites." John Gierach
 
Geoff Blakesley said:
"...be prepared to explain in great detail why you didn't catch fish, being careful to lay it on something that no one else was paying attention to, like the ozone content of the air or electromagnetic interference from satellites." John Gierach
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Thanks Geoff, another couple of excuses to add to my repertoire, the others were beginning to wear a bit thin :p

Cheers, Dave.
 
Jim Foxall said:
The reason that you can transmit pressure by a liquid IS because liquids are not compressible. If you push the break pedal of your the car the pedal does not feel spongy because the hydraulic fluid transmits the pressure you apply by your foot to the brake. The liquid does not compress. If you carry out a pressure test on a cylinder, you fill up the cylinder. You then increase the pressure on the surface of the water in the cylinder. This pressure is then transmitted to the internal surfaces of the cylinder precisely because the liquid is not compressible. Liquids are about as compressible as a solid!

If we are talking of pressure in water, then there are two components, the pressure due to the weight of the water + atmospheric pressure. It is pretty common knowledge that the deeper a submarine dives the greater the pressure on the structure. I would have thought that the difference of a few millibar at the surface, would be of no consequence in water. Food for thought
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Pretty sure you've just told me a formula I've already stated.... If you want to know how much of a change it can be ill tell you. The difference between 950mbar and a 1050mbar day will be a meter in pressure level. At 2 meters abour 85 percent of the pressure will be due to air pressure, not the water.
 
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