As a schoolmaster snapper grows, its ear bones, or otoliths, form
sequential rings, much like a tree trunk, corresponding to different
times in the fish’s life. Each ring in the otolith get imprinted with
chemical isotopes from the waters where the fish had been living during
that period of time—a fishy chemical address book. By anlayzing these chemical clues, MIT/WHOI
graduate student Kelton McMahon seeks to identify which nurseries for
juvenile coral reef fish should be protected.
(Illustration by Katherine Joyce, Woods Hole Oceanographic Institution)