View Full Version : weather and fish

02-12-2008, 09:09 PM
Does barometric pressure play a role in hatches and fish activity-without regard to water temp,or cloud conditions.

02-12-2008, 09:18 PM
Everyone I kow always says that low pressure is good for fishing. Now there are some theories about this idea. One: low pressure is usually associated with rain, clouds, and overcast days. That in itself sure helps the fishing on low pressure days. Now as far as affecting the fish themselves, i doubt pressure matters. They can acclimate to pressure so well i can't see how a high pressure day matters. Look at trout that live in lakes. It is nothing for them to live in 50 feet of water, now that's pressure! However, high pressure days are usually associated with sunny, blue sky and windy days....that can make the fishing tuff..
I think if you really ask the question of what affects trout feeding and hatches you should look at looner tables. Any good deer hunter can tell you that on a full moon, you have to sit in the stand all day, because the deer will move in the middle of the day, and at the middle of night. The farther the moon phase gets from full the more morning and evening orinted the deer get. Until that is you start miving towards the new moon, which starts the opposite affect. I think all animals are affected by the moon phases, hence why the cow standing factor is a factor. If the cows are laying down, id say so are the deer, and the trout...

02-12-2008, 09:54 PM
How can you tell when a trout is laying down? Do they lay on their backs or their sides? Inquiring minds need to know.

02-12-2008, 10:07 PM
I believe they lay on their sides, but they must keep turning from side to side as to keep their tan lines even... Now that is in the northern hemisphere of course, everthing is backwards in the southern hemisphere... kinda like the whole clockwise counter clockwise toilet flush theory..

02-12-2008, 10:16 PM
I have always been told that barometric pressure does have an affect on the fishing. So in order to show this, lets put this into terms we can understand. Let's assume that a front comes through and either raises or lowers the barometric pressure by 1.0" Hg. When you equate this to water level, that is somewhere around 13" of water depth.

We all know how sensitive fish are to water depth. Specifically bass have lateral lines that are highly sensitive to pressure changes. When this front moves through the fish will feel like it is either 13" deeper or shallower in the water column than it was previously. I don't know if trout have this same lateral line system, but I am assuming they have something similar. I can't help that if this drastic of a change is applied to the fish and its habitat it can have a definite impact on the current feeding trends. I do believe this is a temporary result, and after the fish has adjusted to the new pressure feeding will return to normal.

Also, as 2weight stated, we equate low pressure with cloudy skies which we relate to easier fishing conditions.


Rog 1
02-13-2008, 04:46 PM
I haven't seen anything in hard facts but mostly beliefs....I have experienced both trout and bass turn on when a front is moving in and during the first rain and for that reason I have rationalized why I am standing knee deep in water with rain drops beating me...doesn't explain why it happens or a basis but that's my story and I am sticking to it.

02-13-2008, 08:34 PM
One of the most productive days I had fishing last year was in the pouring rain. I couldn't see my dry fly because of the raindrops splashing all around it; I could only guess where it was based on the movement of my leader. And I couldn't see anything below the surface for the same reason. Yet the trout were hitting anything that I threw out there. So, yeah, there's a connection of some kind and I'm happy to stick with Rog's story, too.

Let it rain!

Brian Griffing
02-14-2008, 02:14 PM
Earlier in the thread, 2weightfavorite compared the trout to deer. Continuing with that line of thought, deer get moving before bad weather so that they can get their bellies full before the nasty stuff hits, and then lay on their beds and chew their cud while waiting out the storm. I could very well be wrong, but I had always thought trout had developed the same line of thinking. "If this stuff get really nasty, and the water turns muddy and rough, I may not be able to find any chow for awhile, so I better go and nail that fuzzy looking caddis that's floating over my head for the third time."
Not that trout think in English, but maybe that is an instinct that has become predominant species-wide.

02-14-2008, 06:00 PM
Thanks to all who post somewhat tongue-in-cheek on the LRO boards. One of the things that I enjoy about this forum is how, for the most part, nobody takes themselves or the science of fishing too seriously. And nobody seem to get offended. Keep up the good work.

As to pressure, I agree with the sentiment: that its time to chow, because I may not eat for awhile. But I'm also intrigued by Travis' theory about the effective water column depth. I think it might be more applicable in tailwaters and lakes, but it is an interesting thought. Unfortunately, I'm not able to grasp it completely, so please help me a bit (I just got back from three days in Chicago and my brain hasn't completely thawed yet...). If the pressure is dropping, then theoretically the water pressure at a constant depth would decrease, thus the fish would want to go deeper to maintain the same pressure. I'm not sure I have that right, but I think that would be the end result if Trout had similar features to Bass. So that might not be the answer, but you brought up a very good point that I always wondered about: how do trout know when a front is moving in. From what you said (which should have been obvious to me, but wasn't until just now), the barometric pressure we feel, also must affect the pressure underwater.

That makes sense!! (lightbulb goes off...). Forgive me the aha(!) moment (and rambling). I was worried that I hadn't learned anything new today...

02-17-2008, 06:38 PM
I think that Brian nailed it about why the fish get active. I agree that it seems that the fish always bite better when the pressure is falling. But even a big pressure difference doesn't really seem that big to me. As ChemEAngler said, it is about 13 inches of water that the fish has to move to equalize. Well, at least the fish have that option! Us fisherman don't, and have to to just live with it. I know that old folks seem to sometimes be able to tell if the weather is change in their joints, but other than that, I don't really notice it myself. I think the fish, deer and other wildlife, are tuned into the fact that conditions are changing, and that those conditions may bring about lean times until the weather stabilizes again.

I've seen trout at the Chattanooga Aquarium swim from 1 feet deep to 20 feet deep and back again, over and over. That amounts to huge changes in pressure, and it doesn't seem to bother them. That 20 feet is a far larger pressure change than any weather event could ever produce.