There has been lots of good autecology of crappie in this productive thread. A couple of my references indicate that crappie have 25-29 rakers on the first gill arch compared to 8-12 on rock bass, bluegills, and LMB. Big difference in raker numbers here and evidence why crappie can be good filterers of larger zooplankton such as Daphnia, Diaptomids and Chaoborus (phantom midge larvae). Lots of protein in those "bugs" for the effort expended as Bruce pointed out. Many of these larger zooplankton inhabit the deeper waters during day and migrate to near surface at night.
Ty made a good point about certain body features of crappie make them suited as good planktivours and what he says makes sense. I think black crappie populations usually do better in clearer water because larger forms of zooplankton are common inhabitants of clearer water. Crappie cn feed on these zooplankton when other foods are in short supply. Water in many ponds lakes is generally clearer due of greater densities of the larger filtering zooplankers such as Daphnia and Diaptomids (Chaoborus is predatory). It is starting to make sense why the best black crappie fisheries occur in waters that contain abundances of the larger zooplankters as noted by Bruce and Dave.
