There is a lot here on crappie in ponds. They are an enigma within a conundrum - no easy answers.

I do want to point out the issue of catchability. Lots here on the subject as well and worth looking at wrt your problem. Every pond specie that I know of has a built in fear/harm/stress release indicator or several. When a fish is caught (hook & line) it releases those indicators (visual/chemical/other) and the other fish know to watch out.