Originally Posted by Modest_Man
They do aerial flyover surveys where they count boats fishing and then compare the numbers to the amount creeled at the boat ramps. You can get an estimate of the total number of boats fishing and what percentage get checked by creelers and extrapolate the data gathered at the ramps to the fleet as a whole.
They even have a bit of the equation that takes into account how much lying people do when creeled at the ramp.
That can work reasonably well when there is only one fishery being conducted. Not so good if there is a shrimp opener on a day when crabbing is open. Or boats out shrimping when halibut season is open.