Validation of Annulus Formation in Gizzard Shad Otoliths

Abstract

We used sagittal otoliths from gizzard shad Dorosoma cepedianum collected every other month during a 1-year period from two Tennessee River impoundments to validate the formation of annuli. Marginal increment analysis of opaque bands formed on sectioned and whole-view otoliths verified annulus formation was completed in Aug. However, deposition of opaque bands was evident in Jun. For fish with three or less annuli visible in whole view, annuli counts on sectioned and whole-view otoliths were identical. However, otoliths with four or more annuli in whole view required sectioning to accurately age fish. The body length–otolith radius relation was highly variable, particularly for sectioned otoliths. Thus, caution should be used when interpreting back-calculated lengths from gizzard shad annuli.