Shorty, what causes the fish to go up or down?...
I'm sure it has something to do with swimming around and finning.
Isobars on a weather map indicate barometric pressure gradients, indicating both wind direction and velocity - weather changes – clear to cloudy – warm to colder – precipitation (clear/turbid water) - etc.
All documenting changes in barometric pressure that makes the fish go up or down...
![grin](/forums/images/graemlins/default/grin.gif)