Have heard all my life that the approach of a low pressure area generally announces improved fishing. I have, in fact, witnessed

[crberkey]

Have heard all my life that the approach of a low pressure area generally announces improved fishing. I have, in fact, witnessed such a thing several times. So the obvious question is, if water is not compressible, how do fish know a front is approaching...high or low pressure?

[madmax]

Think of the water and the air above it as if it were one fluid body (with two densities) above the fish and extending all the way up to the exosphere, about 75 miles up. The sum total pressure on a fish is the weight of the water in the column above it plus the weight of the air above that. Water doesn't compress, but it can have greater pressure on the fish in it if there's more pressure being exerted on it from above by the air, and the reverse is also true. In a hurricane, which is basically a massive low pressure system, the sea can be lifted up above normal level by this lowered air pressure as much as several feet, adding to the storm surge.