I have read on the forum of turning off the feeder for a few days and that makes the subsequent fishing better. (I suspect that is true, but don't know how long you could turn it off before you would start to weaken their good habit of eating at the feeder?)

Also, do you have a good spot near the feeder to sink a few cedar trees in deeper water that does not negatively impact any of the OTHER things you do in that area of the pond? I think having a fish "concentrator" near the feeder would make it easier to just catch one or two crappie so you could sample your population.