Barometric Pressure in Summary

[Bonefish]

Barometric pressrue (BP) is the atmospheric pressure pushing down on the earth, and this pressure is measured by a barometer. Low pressure areas have less atmospheric mass above their location, whereas high pressure areas have more atmospheric mass. As elevation increases, there is less overly atmospheric mass pushing down on the earth's surface. The atmospheric pressure is not the sam everywhere on earth because of the earth's uneven heating and cooling. It is the warm air ascending and the cold air descending creating wind that causes uneven atmospheric pressures on the earth's surface. Air mass may be in valleys or mountains which produce high or low pressure areas. Air mass may flow from areas of high pressure to low pressure and be influenced by the eath's rotation. When air rises, it cools and moisture condenses causing the BP to drop.

There are two types of swimbladders in fish: open and closed. There are some fish on this earth that have swimbladders which regulate buoyancy by tissue, bone and scales. The closed type has a "gas gland", and the open type has a "pneumatic duct." Bass have a closed-system and carp have an open-system. The closed-system functions by a complex anatomical and physiological mechanism of "osmo-chemical-pressure-regulation." The open-system involves a "pneumatic duct" connect directly to the esophagus. The close-system adjusts bladder volume by gas transport into and out of the circulatory system. The open-system adjust bladder volume by gulping surface air and then belching air. Bladder function is to maintain neutral buoyancy in the most energy efficient way.

Even though water does not compress, the surrounding area around water can be compressed thus affecting any air-filled space in or around it. Bass can detect the slightest of pressure changes in the atmosphere through the water. Fish with closed-systems don't readily adjust to atmospheric pressure changes, whereas open-system fish do. Closed-system fish may make quick vertical trips to the surface but must return to their comfort level. Closed-system fish that live in shallow lakes may develope anatomical and circulatory compensation to allow them to adjust to acute changes in atmospheric pressure in a shorter amount of time. It is like a failing heart that lays down collateral arteries and veins to by-pass blocked vessels.

As far as fishing goes, fish can feel the slightest change in atmospheric pressure. The direction of the wind doesn't affect active feeding fish. A sudden change in wind direction and/or force is usually an indication the BP is changing which will affect fish behavior. Shallow water fish are more affected by atmospheric changes than deep water fish. After a storm when the barometer is rising, fish move to deeper water to avoid bladder discomfort. Increased bladder pressure makes fish lethargic and not feed. As a general rule in the warmer months, fish shallow water during prefrontal and frontal condtions and fish deep water cover and structure during high pressure periods. When bass are holding tight to cover and structure, use smaller lures and slow down the presentation.

If a stable high pressure weather pattern has been around for a few days, and a front starts to move in causing the barometer to start falling, it is time to go fishing. After long periods of high pressure, fish will once again start to feed because they have had time for their bladders to equilibrate. Bladder compensation varies with species of fish and lake depth, which is usually anywhere from 4 to 48 hours here in Kentucky. In the spring and fall, fish behavior can be unpredictable because of the spawn and lake turn-over. Changing weather conditions may not affect fish like they do other times of the year. Spawning fish may not travel very far from spawning grounds during high pressure days. After the fall turn-over, fish will be feeding heavily and stay in shallower water. During post-frontal-high-pressure days, wind can force more dissolved oxygen into the surface water attracting feeding shad. Murky, windy, sunny banks in the spring can be big producers because the water is warmer, oxygen content is higher, and the muddy water provides a place to hide from prey. But windy days can be good any time of the year except for the coldest days of winter. When bass go deep after a front, try flipping, shakyheads, jigs and drop-shotting techniques when they are holding tight to cover and sturcture.

[slowride]

thanks bonefish u da man, also i hear channel 13 is looking for a new meteroligist.......just a thought

[fishhound]

thanks! found it to be educational..

[RoadToad]

Very informative. Thanks, Bonefish. Know of any web sites with good pictures? And what other species have open v. closed systems?