Atmospheric pressure and bite activity

[JasonGotaProblem]

Its undeniable that there's a relationship between atmospheric conditions and fishing success. It's pretty reasonable to say that barometric pressure has a strangely large effect on fish behavior. It also seems reasonable to say that the how the pressure is changing seems more important than the current mercury reading. But beyond that, solid statements seem to get kind of murky.

Do different species of fish react differently to different barometric conditions?

Is it actually the pressure driving fish behavior or is it some other factor but pressure is also related (aka it's a correlation not causation)?

What else am I missing? 

[Gfish]

Good questions. I heard that an increasing barometer(higher air pressure) makes the oxygen concentration in the water go up, stimulating more activity in the O2 using critters.

But if you think about all the factors that might influence fish activity/distribution who knows what does what? Temp., Ph, salinity, photo-period, currents, etc., etc.

[nelz]

It's all about yesterday. You shoulda been there yesterday. 

[MarkT]

Don't forget the moon phase!  It certainly has an effect too.

[Benni3]

Biometric,,atmospheric,,,moon,,,cloud cover,,humidity,,temperature,,,,water temperature,,,,water levels rise or on the drop,,polushion,,,, but knowbody knows how it going to effect your fishing for the day,,,,,,

[JasonGotaProblem]

Well this weekend will be an interestkng one. Full moon, which in my experience doesn't bode well. And remarkably low pressure, which is also considered bad. But ill be by the water and i have no self control. So we'll see how it goes.

This was intended more for general discussion than about my weekend plans. But my weekend plans are what got me thinking about it.

[jurelometer]

Ooh, a sciencey question.  Cannot resist-aaargh...

I am in the "nope" camp.  Fish do respond to changes in weather, but changes barometric pressure is pretty much not detectable for a fish. It gets lost in the constant pressure change noise.

Significant barometric pressure changes are usually going to coincide with other weather related changes like cloud cover, wind (and therefore waves), rain, etc.  It seems more plausible that these other environmental changes that do effect the predator/prey success equation,and therefore effect feeding behaviors, are the actual triggers.

Let's define what constitutes  a significant change in barometric pressure.  After looking at a couple weather sites, I am going to go with over 7mb (about 0.1 PSI) over several hours.  That is about a 7/10s of a percent change  in pressure at sea level. Pretty hard to be consciously detected by a land based animal, but maybe...

The difference for marine life is that water is much more dense than air and the amount of water above a fish is going to be constantly changing. A slight change in depth (like about 2 inches) will be the same as that 7mb change in air pressure. So as the depth changes from the fish moving up or down, or waves (even just ripples) passing  above the fish, the pressure experienced is constantly changing, and a small change in the background over a long period of time will be impossible to detect without some fancy equipment, a spreadsheet, and a brain larger than a pea.

Even if there were significantly higher oxygen levels in seawater related to modest changes in pressure (which I am kinda skeptical on) - the above would still apply.

Don't forget the moon phase!  It certainly has an effect too.

Don't get me started on moon phases 

It's all about yesterday. You shoulda been there yesterday. 

Can't argue with this.   And even if the fishing is good today, well... today is just tomorrow's yesterday.

-J

[JasonGotaProblem]

Don't forget the moon phase!  It certainly has an effect too.

Don't get me started on moon phases 

I'm convinced moon phase does have an effect. If there's a bright moon in the sky at night, they can see snacks all night long so when your sketchy snack for them comes along they're not exactly starving enough to gamble on a maybe anymore. Real scientific i know

[ExcessiveAngler]

I always do awesome a few days before and after the full moon, especially targeting stripers and black drum, which I've currently been doing!
Been catching all kinds of flounder, on the boat as well and big ones too!
We even ran into some weakfish up here this week, that was nice to see them as well!
I am a firm believer on catching on the low pressure. It seems for me, especially with a storm coming in.

[MarkT]

A slight change in depth is what you get with the tide change! That affects the current and without current the fish don't bite! No flow, no go!

[philaroman]

sometimes I sits & thinks 'bout pressure...   sometimes I just sits

either way, if I sits by the water with rod/reel, I feels better 

[Gfish]

The only 1/2-way predictable fish behavior I know about are the anadromous salmonids. Certain months of the year and a good dose of rain and they enter the rivers. Wonder if the lunar phase affects that?

I know that the smolts will head back down towards the ocean and it seems to be; age, time of year(April best on the N.Coast)and Lunar Phase(new moon best, if I remember right).

[Midway Tommy]

I am a firm believer that if you're not on the water you're not going to catch any fish, regardless of the barometric pressure, moon phase or cloud cover.      

[ExcessiveAngler]

Ooh, a sciencey question.  Cannot resist-aaargh...

I am in the "nope" camp.  Fish do respond to changes in weather, but changes barometric pressure is pretty much not detectable for a fish. It gets lost in the constant pressure change noise.

Significant barometric pressure changes are usually going to coincide with other weather relate changes like cloud cover, wind (and therefore waves), rain, etc.  It seems more plausible that these other environmental changes that do effect the predator/prey success equation,and therefore effect feeding behaviors, are the actual triggers.

Let's define what constitutes  a significant change in barometric pressure.  After looking at a couple weather sites, I am going to go with over 7mb (about 0.1 PSI) over several hours.  That is about a 7/10s of a percent change  in pressure at sea level. Pretty hard to be consciously detected by a land based animal, but maybe...

The difference for marine life is that water is much more dense than air and the amount of water above a fish is going to be constantly changing. A slight change in depth (like about 2 inches) will be the same as that 7mb change in air pressure. So as the depth changes from the fish moving up or down, or waves (even just ripples) passing  above the fish, the pressure experienced is constantly changing, and a small change in the background over a long period of time will be impossible to detect without some fancy equipment, a spreadsheet, and a brain larger than a pea.

Even if there were significantly higher oxygen levels in seawater related to modest changes in pressure (which I am kinda skeptical on) - the above would still apply.

Don't forget the moon phase!  It certainly has an effect too.

Don't get me started on moon phases 

It's all about yesterday. You shoulda been there yesterday. 

Can't argue with this.   And even if the fishing is good today, well... today is just tomorrow's yesterday.

-J

Well, I'm no scientist by any means lol!
But I've read many many articles over the years that would have to disagree with your theory!
How can the fish not feel the pressure when the air is pushing down against water?
Especially if they're up in the shallows!
I remember one article distinctly, talking about something about their air bladder changing with the barometric pressure!
Guess it's time to hit the web again lol!

[jurelometer]

I am a firm believer that if you're not on the water you're not going to catch any fish, regardless of the barometric pressure, moon phase or cloud cover.   

Exactly.

It took me a while, but I also decided that the best strategy is to go fishing when you can.

Well, I'm no scientist by any means lol!
But I've read many many articles over the years that would have to disagree with your theory!
How can the fish not feel the pressure when the air is pushing down against water?
Especially if they're up in the shallows!
I remember one article distinctly, talking about something about their air bladder changing with the barometric pressure!
Guess it's time to hit the web again lol!

There is plenty of BS out there in the fishing media when it comes to the science. I would suggest looking to the scientific literature.  If you find something on the scientific side, I would be grateful to be corrected.

A swim bladder is an elastic sac filled with (mostly) oxygen.  The volume of oxygen (and therefore the bladder) will expand and contract with the ambient pressure change.  So the presence of a swim bladder  doesn't affect the basic issue.  The problem remains that barometric pressure changes are too small and slow to be significant  amongst all the other much larger and more frequent pressure changes occurring.

Regarding depth: A 7mb change in surface pressure from a  two inch ripple passing over in an instant, or a 7mb barometric pressure change over several hours  will cause the same ambient pressure change (about 0.1 PSI) if the fish is at 1 foot or 1000 foot depth. The only difference is that the change as a percentage of the total ambient pressure will be different.  So yes, a fish that is closer to the surface is more likely to notice a small change, but this still doesn't change the fundamental issue. 

A bit more on swim bladders in most fish species:  The fish will  slowly adjust the amount of oxygen in its bladder to maintain relatively neutral buoyancy, but it is a somewhat slow mechanism, relying on changing the acidification levels in the blood to excrete, or absorb oxygen into or from tissue, including the bladder walls which is more oxygen permeable than other tissue. Or something like that .  The purpose of of a swim bladder is to conserve energy  by not having to swim up or down to maintain a desired depth.  If you have done any scuba diving, you are already aware of the amount of energy required to maintain a specific depth if your buoyancy gets too far off kilter, but a little bit off doesn't matter so much. A swim bladder is very analogous to a diver's BCD.

Not a marine biologist myself, so any corrections from folk that are edjumacated in this stuff is appreciated.

-J