That's correct. For crappie, bluegill and shad we can read otolith (ear bone) rings like tree rings are read for aging. We use sections of catfish and carp spines for aging, and we use scales for bass, instead of otoliths, for this project. Each year fish lay a growth ring down on a scale, otolith or spine. We are able to read daily growth rings on young fish as well, if necessary.