The High’s and Low’s of Fishing
By Capt. Cefus McRae, Nuts & Bolts of Fishing
The recent winter storm had me sitting by the fire for a full day, watching the sleet and freezing rain accumulate on the trees. Over time, the limbs began to sag under the weight, and occasionally I would hear what sounded like a firecracker followed by a loud thump as limbs snapped and fell to the ground. Mother Nature at work.
Our ice storm was the combination of layers of cold and warm air, and a moisture-rich low pressure system that started as snow in the upper layers; hit a layer of warm air and turned to rain…then hit another layer of cold air below and turned to sleet and freezing rain. The result was about three days of power outage, icy roads and listening to the generator gently purring on the downstairs patio. Interestingly, because our internet lines are buried, we still had cable TV and internet.
For some reason, I also began to think about some of my best fish-catching days; and how there might be similarities to this recent weather system. I remembered some of my best fishing days happened during cloudy, overcast days. In fact, one of my best striper fishing days occurred when it was snowing.
(The author and buddies with a Watts Barr striper on a snowy winter morning)
With lots of time on my hands, I started surfing the web and discovered just how many rabbit holes one can dive into when trying to research a topic. My query was simply…”How does barometric pressure affect fishing?” Oh my! What a can of worms this opened up. I realized long ago, if you’re looking for something on the web, you can eventually find the answer YOU want. It may not be the correct answer, but you’ll find a website that agrees with your point of view. In this case, I wanted a truly scientific explanation. The truth is…I never really found one. Just lots of postulates that came across as factual, but none of them really had me convinced. Then, I remembered what my grandfather would say…”Changing weather changes the fishing”. That much I know to be true. But why? The fish are already wet, so rain shouldn’t affect them. A passing storm system doesn’t dramatically affect the water temperature in a large lake or the ocean. It has to be something else. Maybe it’s the barometric pressure. But can fish actually feel subtle changes in atmospheric pressure deep below the surface?
Weather fronts bring changing barometric pressure
Growing up, my uncle had a bad knee. An injury from his school days. He said his knee would hurt before a storm came in. My grandmother dealt with arthritis, and said she could predict rain because her joints would hurt when it was on the way. Apparently, when a weather front associated with low atmospheric pressure approaches rapidly , the fluids and tissues around your joints begin to expand, and that puts pressure on the nerves causing pain for folks who have joint-related problems. Let’s translate that to the body of a fish. They have lateral lines to help them find food, detect water movement and water pressure. They also have swim bladders to help them adjust buoyancy. An interesting side note here: sharks, rays, flounder, most catfish and tuna do not have swim bladders. Want to know why? Google it, and go down about forty rabbit holes for the answer.
Most biologists agree these sensory organs can detect even the slightest changes in water pressure, and signal the fish that it’s time to grab a bite before conditions worsen. It might seem impossible for a fish in the water, especially snapper and grouper who live 50 to 100 feet down, to feel just a couple millibars of atmospheric pressure? By the way, one millibar of pressure equals 0.0145 pounds per square inch. That sounds almost imperceptible.
But in the water everything changes. I know from snorkeling that I can’t equalize beyond about 15 feet. It’s something with my ears. Anything below 15 feet, and my head feels like it’s about to implode. The deeper I go, the worse it gets. That’s hydrostatic pressure, which is the force exerted by a liquid on an object…my ear drums. Now do the math. The water itself has weight, creating pressure. And that’s compounded by the weight of the air on the surface water. Yes, air has weight. It’s 14.7 pounds per square inch. The weight of the air ultimately adds to the pressure in the water below. High barometric pressure, typically associated with fair weather and bluebird skies is denser, and serves to slightly increase the surface water pressure. It literally pushes down on the surface, and that impacts the pressure in the water. It’s slight, but it’s there nonetheless. Imagine it’s like adding that one small straw that breaks the camel’s back. Conversely, low pressure systems bring less dense air, reducing weight on the water surface; ever so slightly reducing the water surface pressure and consequently the same at depths. Yes, these are very small changes, but evidently fish can sense them.
Once I wrapped my head around that concept, it actually seemed backwards. Low pressure makes my uncle’s knee hurt and my grandmothers arthritis flare up. But it makes fish bite. What gives? Some biologists say low barometric pressure causes their bodies to expand, and they feel hungry. Some say the low water pressure allows plankton and smaller critters to float off the bottom and up through the water column…triggering a feeding frenzy. And there are dozens of other theories. Whatever the true scientific explanation, I do know that gamefish tend to actively feed a day or so before a low pressure front arrives. And when it actually gets here, the bite slows down measurably; often shutting down for several days until the weather stabilizes.
Similarly, the consensus is that high pressure systems make fish feel like they have a stomach ache. And as a result, don’t want to eat for a few days once the skies clear up from a storm.
But fish are resilient. They go through a lot. They deal with seasonal temperature changes, fluctuating dissolved oxygen levels, changes in water clarity and suspended particulate. These seasonal changes occur over time, and they have an opportunity to gradually adjust. Weather fronts happen quickly, resulting in rapid changes to their environment. As weather systems stabilize, they adjust to the conditions and go on with their daily lives. Remember, they have to eat. But it takes a few days for them acclimate.
In reality, the moon and sun probably have a greater effect on feeding and spawning times. The moon determines our tidal swings, and the amount of daylight influences spawning seasons as well as surface temperatures. Again, these are gradual, seasonal changes. Whereas storm fronts come on rapidly. I believe it’s the rapid change that influences feeding (or non-feeding) activity. But that’s just my theory.
The author with South Pacific mahi-mahi as a storm front approaches
So, after a day spent sitting by the fire and going down dozens of rabbit holes on the web, I’m not convinced I got all the answers to my simple question. But I did come away with a lot of information…how much was correct will warrant further research on the water. And that’s what I’m looking forward to after the boat thaws out.
Want to see the Nuts & Bolts VIDEO that goes into more detail? CLICK HERE TO WATCH THE HIGH’s & LOW’s OF FISHING
Tight lines and calm seas,
Capt. Cefus McRae