I'd be interested to know what the purpose is of the various surveys..are that a broad bassed survey or are they for something specific.
as far as a broad bassed survey, the times when the surveyors are at the ramps would skew the results.
If surverys were only taken on weekends during the day when boat trafic was high.....it may overestimate the fishing effort, but under estimate fishing sucess.
and if the regular surveys are done at particular ramps..well the whole demographic would be skewed to the situation at that particular ramp.
interesting.
cheers