[jimk]

I've always heard that lower pressure or a pressure drop means better fishing. Yesterday(4th) was the lowest pressures I've seen up and down the coast for awhile....down to 29.9* from 30.1* the previous couple of days. This was markedly lower and I'm curious if the fishing was markedly better...the storms made it difficult but yesterday afternoon should have been pretty good, maybe even spectacular. Anyone able to verify this??

 

[backlasher]

I've always heard that higher pressure was better for fishing. I guess we should just go whenever we get the chance!

 

[Melon]

Yesterday was great. Trout hammered everything we threw at them. Biggest problem was size and that thunderstorm rolling right up Trinity Bay on us. Great trip all in all.

 

[bill]

I don't know the science behind it, but it works. Over the last few years I have quit looking at charts/data/tides ect, and just went fishing.
We did see several hookup's at the Seabrook Lagoon yesterday afternoon, so that is proof there is something in the pudding.

 

[troy merrill]

Lower pressure conceptually makes more sense to me.

 

[LIONESS-270]

Don't know about saltwater...But its the opposite here at the lake when you are catfishing....Rod or Trotline...In 5yrs, 2 factors that have always meant great catches (about 90% of the time) has been High Press. and on the rise......Plus a ripple or better on the water...

 

[Jolly Roger]

We have discussed this topic a few times. Lot of info, but no real proof either way. From experence I know that a falling pressure triggers a feed, but have no proof.

I have my own theory, someone called it a darwin aproach, bu it makes sense to me.

http://2coolfishing.com/ttmbforum/showthread.php?t=48200&page=1&pp=10&highlight=pressure

 

[Jolly Roger]

Don't know about saltwater...But its the opposite here at the lake when you are catfishing....Rod or Trotline...In 5yrs, 2 factors that have always meant great catches (about 90% of the time) has been High Press. and on the rise......Plus a ripple or better on the water...

Would make sense that inshore or nearshore species of fish would be greater influenced by pressure then fresh water fish. Pressure is about the only warning a trout or red has that a hurricane is coming.

 

[mastercylinder60]

29.92" of mercury is actually considered to be the average atmospheric barometric pressure at sea level. water is very dense and very difficult to compress, therefore, pressure has little effect on the water itself. however, barometric pressure can have all kinds of effects on fishing - from the weather above you as you fish, to the oxygen saturation level in the water.

here, this is a good article: Effects of Barometric Pressure

 

[Jolly Roger]

I agree with the chart on the link mastercylinder.


Everyone says that barometric pressure will have little effect on water. But my question is what about the air pockets in the water that fish have aka air bladers, stomachs, and just the flesh of fish will compress. Since water has almost no compression, then it would transfer the weight of the air pressure to the fish. It would seem that any change in airpressure could be felt by fish. Since water does not compress the higher pressre would be felt evenly throughout the water colum.

I can not get a clear answer on this. So maybe someone can help. If water does not compress and it is a liquid, then any weight added to the top would be felt on the bottom. So a fish inside the water would fell the pressure change on all sides. This would in fact multiply the pressure by at least 4. So one pound of change at the surface would be 4lbs of pressure in the water if you had a pocket of air trapped in the water?

 

[mastercylinder60]

well, roger, that's a good question, but let me ask you this: if water is extremely difficult to compress, with air pressure having little effect on the water molecules themselves, what kind of effect would atmospheric air pressure (above the water) have on a fish below the water? how could it transfer the weight to the fish if he is in an enviroment that is virtually uneffected by rather small pressure changes of the atmospheric pressure?

 

[Jolly Roger]

I think of it this way.

Two sheets of metal, between the metal are two ballons. You have 30lbs pushing down even across the metal. The ballons are going to compress to a certin spot then the weight will be transfered through. If you add one more pound of weight, the ballons will feel the weight. But the metal sheets have not compressed, only the ballons between them.

If water does not compress, it will transfers the weight of the air. Anything that is in the water that will compress. Like pockets of air or flesh will feel the pressure change. Since water is a liquid, then all sides of the fish will feel the effect, so it will be muliplied to some degree. I would assume that water some some small degree of compression, so deeper water would be less effected by air pressure. I know high pressure will push water down, out and away. And low pressure will allow for larger waves, like in hurricanes. So in my mind it only makes sense that changes in air pressure are felt by fish much better then some believe. I am a common sense type of person, not an expert on the subject. But if you push down on a hard object that has softer objects between you and the ground. The softer objects will be effected by the added pressure.

 

[mastercylinder60]

but, you can't make that analogy. you are comparing a relatively large amount of force (30lbs) pressing against a very small amount of resistance (the air in the balloons) in a very concentrated spot to a relatively minute force against a huge amount of resistance. as they say, you can't compare apples to oranges.

if i put you between those same pieces of metal and applied 30lbs of force, you'd feel it. can you feel the change when the pressure drops from 30" hg to 29"?

 

[Jolly Roger]

The air in fish would be the same as air in ballons?

If I rember right 30lbs per squre inch is the same force on water as it is on steel. If water did compress, seems it would be harder for fish to feel the pressure change. The fact that water does not compress and is a liquid means that the pressure is distributed throughout the water colum. So any thing that is in the water that does compress aka air bladders, flesh will feel the change.

Think of the metall the size of the ocean and the 30lbs pushing down as the air pressure. The ballons repersent air bladders in fish. Both metal and water do not compress. But metal and water both transfer the pressure aka hydraulics. So in water or between metal the ballons will feel any pressure change. With water being a liquid this pressure change would be felt more.

I do feel better when the pressure is low, but I am outside almost every day of my life. So weather is important to me. I can not feel pressure change. But it does not effect wether I live or die.

If you read the link I posted I have a simple theory. Over large amounts of time hurricanes and other strong storms came and went. In there path they killed fish by the millions. Fish that sensed the lower pressure learned to feed at that time to make it through the storm. Over this huge amount of time the ones that feed during the low pressure that comes before a large storm survied to make babys. The ones that did not died. So the great bite that occurs when the pressure starts to drop is a instinct that fish have developed over millions of years.

 

[jimk]

I had to look this up...most fish have gas or air bladders that control its buoyancy....bring up a deep water fish very rapidly and it expands out the mouth due to lower pressure. One atmosphere of air exerts about 14.7 psi....at 29.92 inches of mercury or at 1013.25 millibars...so the weight of the air exerting 14.7 psi on the water and the weight of the column of water above the fish should be felt by the fish...during high pressure times the fish has to increase the pressure in its bladder and conversely decrease it during low pressure, if it wants to remain buoyant at the same level. For something that has a brain about the size of a BB, this is getting complicated .... somehow, this all relates to better times to go fishing. I wish I understood it better.

 

[mastercylinder60]

The air in fish would be the same as air in ballons?

So any thing that is the water that does compress aka air bladders, flesh will feel the change.

Think of the metall the size of the ocean and the 30lbs pushing down as the air pressure. The ballons repersent air bladders in fish. Both metal and water do not compress. But metal and water both transfer the pressure aka hydraulics. So in water or between metal the ballons will feel any pressure change. With water being a liquid this pressure change would be felt more.

So the great bite that occurs when the pressure starts to drop is a instinct that fish have developed over millions of years.

yes, but we started out talking about the effects of atmospheric pressure on fish, not water pressure. if you've ever been scuba diving, you know that water exerts tremendous amounts of pressure. the deeper you dive, the greater amount of mass of water on top of you, and you can certainly feel the force in your ears.

unlike the atmosphere which exerts very small amounts of pressure on its surroundings, water exerts tremendous amounts of pressure due to its huge mass. this hydraulic pressure is why fish have swim bladders. the deeper a fish dives, the increased pressure from the water on top of him pushes gases from his blood stream into his swim bladder making him more buoyant, making the fish equal in density to the density of the water surrounding him.

but, this has nothing to do with the atmospheric pressure on the water from above, which is imperceptible to a fish.

 

[Jolly Roger]

Some believe that the reason that the air pressure should have no effect on fish is that if a fish swims a few feet vertical in the water colum then it has just increased or decreased the pressure greater then what air pressure can effect it.

This is true, only takes a few feet of water to eqaul the amount of air pressure change that we are talking about. This point is fact. But they tend to leave it at this that just say that because moving up and down in the water is greater then air pressure changes, then it should have no effect on fish.

But I tend to dis-agree. Moving up and down in the water is controlled by the fish. The air pressure is not, so they have learned by using air pressure changes when the best times to feed are by evolution.

 

[Jolly Roger]

yes, but we started out talking about the effects of atmospheric pressure on fish, not water pressure. if you've ever been scuba diving, you know that water exerts tremendous amounts of pressure. the deeper you dive, the greater amount of mass of water on top of you, and you can certainly feel the force in your ears.

unlike the atmosphere which exerts very small amounts of pressure on its surroundings, water exerts tremendous amounts of pressure due to its huge mass. this hydraulic pressure is why fish have swim bladders. the deeper a fish dives, the increased pressure from the water on top of him pushes gases from his blood stream into his swim bladder making him more buoyant, making the fish equal in density to the density of the water surrounding him.

but, this has nothing to do with the atmospheric pressure on the water from above, which is imperceptible to a fish.

Air pressure is weight, weight is transfered by the water. The weight of air is greater then you give it credit for. 15 Pounds per squre inch is weight, air or not. This pushes down on water, changes in this weight aka air pressure are felt by fish.

 

[rvj]

A study was being done on some red fish on the louisiana coast on the effects of low pressure. the reds were tagged and being tracked. hurricane katrina and rita showed up. All the reds prior to both hurricanes moved directly out of the marshes into deeper water and most into the deeps of the gulf. three two six days later they returned. Low pressure will move them into deeper water, and how deep depends on how low the pressure is...

 

[jimk]

One atmosphere exerts 14.7 pounds per square inch at sea level....so if the top of my square head was even with the surface of the water, it has 14.7 psi. For every 33-34 feet down, the pressure increases another 14.7 psi. Since water is basically incompressible, a fish's need to change its buoyancy height in a water column would come only from the variable pressure ingredient....that would be the atmospheric pressure. Right??