Back in the early 80s when I was learning the ways of catching the “three Bs” of Southern California sportfishing, I was given the following advice by an old salt aboard the GW from Seal Beach Pier while returning from a local cod trip: “Watch Dr. George on TV and when he shows you that big “L” on the weather map moving our way, that’s when you need to come out fishing!”
The big “L” on the weather map he was referring to is an area of low pressure. The line of thinking is that when a significant change in the weather is about to take place, such as when that low pressure area moves in, fish can sense this and begin to feed more aggressively ahead of the stormy weather.
So, is this true or just one of those stories that gets handed down because it sounds logical?
I’m inclined to believe it’s a little of both, but for different reasons.
Water exerts a tremendous amount of pressure. Much more so than air. The atmosphere typically produces a pressure of 14.7 PSI (pounds per square inch) at sea level. That pressure is doubled by heading just 34 feet underwater!
Fish can obviously sense changes in underwater pressure as they move up and down in the water column. An internal organ called the swim bladder allows them to rapidly compensate for pressure changes as the depth changes.
That’s great for the underwater world where fish live. But what about those air pressure changes I talked about at the beginning of this column? Let’s put it this way: A large storm moving in would result in an air pressure change over a number of hours that would be equal to a fish diving down about 1 foot. That is an above-water change that would hardly allow a fish to detect underwater, especially for deep-dwelling rockfish or deep-diving tuna.
Furthermore, when asked about a possible fish-barometer connection, the fish experts at the Birch Aquarium at Scripps Institution of Oceanography said they were unaware of any link.
The Net Result
It’s what comes with that pressure change that more likely has an impact on a fish’s feeding behavior…and the anglers who chase after them: Wind, waves and light.
It sometimes keeps us off the water and churns up the top levels of the water column. That results in upwelling (temperature change) offshore and reduced visibility inshore.
How many times have you heard this offshore: “Weather is UP and the fish are DOWN?” I think there is more truth to that statement than fishing by anticipated changes in atmospheric pressure.
It is possible that some shallow water, back bay dwelling species *may* be affected by barometric changes, but factors such as water temperature and tidal swings will likely serve as better fishing forecast tools than the barometer.