>>I don't think barometric pressure has much effect on fish directly. A fish has only to swim through a depth in the water of a couple of feet and it experiences a far greater change in pressure than on the scale of a barometer.<<
Ron, if you walk into a room with an open fire, you feel the temperature rise but you are not concerned because you are expecting it. If you are sat down minding you?re own business and you feel the temp rise then you are concerned because there is no reason. The pressure sensors along the lateral line of fish are perfectly capable of detecting very slight variations I pressure.
The question we should be asking is why would some fish respond to changes in atmospheric pressure?
Most of you will be familiar with the FM Venue reports and those of the Ribble, 900 plus postings over four seasons. I?ve now popped all these onto one spreadsheet (15.6Megabites) along with river levels (taken every 15 mins for the last four years, curtsy of the EA) moonrise, sunset and sunrise times and also average barometric pressure (however the web site I?ve down loaded this from only goes back 1-1/2 years, they do a hourly range but I?ve not yet downloaded this). It is possible now, for anyone who?s got the time, to analysis catch rates against weather conditions for the Ribble.
I could if I was minded, and had the time, plot for any one of the Ribble sessions the river levels and barometric pressure for 5, 6 or any number of days prior to that session.