14 replies to this topic

[lilyea]

The eye of Hurricane Irma went directly over us while it was listed as a Category 2 hurricane and after a week without electricity we finally have power back.  Thankfully we remained safe and didn't have any property damage.  Additionally I didn't lose any fish but the massive daily water changes provided a significant workout.  

 

During the storm the barometric pressure here dipped to 28.38 (961 mbar).  Although this isn't nearly as low as Hurricane Wilma (2005) that reached 26.05 (882 mbar), this is still well below average for this area (30.03 in. or 1017 mbar).  I realize that there is a difference between water pressure and air pressure, but I know that the change in air pressure has an effect on many tropical fish species including many catfish and loaches.  My question is what are the effects of low pressure or change in pressure on any North American native fishes?  Are there any specific academic papers that address this issue?  Any specific anecdotal experiences?

[Matt DeLaVega]

LOL! Get on an an angling forum. I bet you would get a plethora of interesting theories. I would also be curious about any scientific data about this, most of what I have heard is similar to things like if you see maple leaves upside down, it is going to rain.

[JasonL]

Supposedly barometric pressure changes have effects on the swim bladder pressures of many native fishes that can lead to minor behavioral changes such as going up or down in the water column. I believe most of this is anecdotal speculation though.

What is clear to us anglers is that a drop in barometric pressure (usually from an upcoming storm) has a really positive effect on the bite. Whether this is from the barometric pressure per se vs. the actual whether system (eg. rain washing in food particles) I'm not sure but it definitely happens.

[gerald]

The pressure drop also temporarily drained some creeks and rivers in the FL panhandle, as the low pressure to the south "pulled" the water into the Gulf, much like a seiche in the great lakes.  I saw some photos of manatees left stranded in the Wakulla River.

[centrarchid]

I could see a reduction in the ability of the water to hold oxygen like you see with changes in altitude.  Fish I am guessing would realize little unless the pressure drop lasted more than a hour or so unless water volume relatively shallow.  Impact on swim bladder would be modest and not unlike swimming a little bit up in the water column.

[zooxanthellae]

There is a paper out there from the early to mid 2000's describing the behavior of tagged sharks before during and after a hurricane. I don't remember specifics, but the authors did attribute movement to barometric pressure changes. If I remember correctly, the sharks all fled for deeper water.

[az9]

I tend to be really skeptical on things like this but yet can't explain the behavior of fish AFTER a cold front went through on a lake I used to fish at night for trout. The fish tended to suspended in the thermocine in 18 to 24 feet of water, and we would catch them under lanterns anchored in deeper water. The best fishing was hot muggy summer nights BEFORE a front came through. What I could never explain was the lack of success AFTER a front cam through. I can understand the usual explanation for a lack of bite during the day after a cold front as in bluebird skies causing excessive sunlight and dropping air temps along with water temps, but this was not the case in the summer at night. Obviously it was dark and the fish were too deep to be effected by air or water temp changes. The only other variable I can think of is the barometric pressure which directly effected the fish or the zooplankton in the water column. 

[don212]

The pressure drop also temporarily drained some creeks and rivers in the FL panhandle, as the low pressure to the south "pulled" the water into the Gulf, much like a seiche in the great lakes.  I saw some photos of manatees left stranded in the Wakulla River.

that was actually wind action, and it was amazing and unanticipated.

[don212]

i think most animals can detect barometric pressure changes, and react to the impending storm in species specific ways, 

[az9]

i think most animals can detect barometric pressure changes, and react to the impending storm in species specific ways, 

 

Apparently they do but how? 

[gerald]

Any semi-sealed gas chamber in the body can detect pressure changes:  swim bladder in fish, eustachian tube in mammals, not sure what structures are used in other animals.

[az9]

Makes sense. Must be very sensitive to feel pressure changes under water where one would think the pressure of the water would be substantially more than the air. Or perhaps the water pressure accentuates the pressure change in the swim bladder? 

[lilyea]

I think it relates to the water column.  Someone please correct me if I'm mistaken, but I think that a change of 1 inch in mercury on a barometer is equal to a 1 foot comparable change in the water column.  Therefore, a drop from 30.15 to 29.15 on the barometer would be the equivalent of lowering the fish one foot in the water from a pressure perspective.

[gerald]

From a fish's perspective, an air pressure drop of 0.2 psi during a storm (= 0.4 inch Hg = 14 millibars) would feel about the same as rising 6 inches in the water.  [34 feet of freshwater ~ 14.7 psi, so 0.5 ft water ~ 0.2 psi]

 

Bruce -- I think you meant to say "equivalent of raising the fish ..."  since a drop in pressure is equivalent to LESS water depth.

[lilyea]

Bruce -- I think you meant to say "equivalent of raising the fish ..."  since a drop in pressure is equivalent to LESS water depth.

 

Of course.  Thank you for the correction.  I should have said a drop from 30.15 to 29.15 on the barometer would be the equivalent of RAISING the fish one foot in the water from a pressure perspective.  

 

​This should be able to be duplicated in an artificial environment so I'm surprised that I haven't found any journal articles describing the results.