Daily Otolith increments in juvenile tropical Parrotfishes and Surgeonfishes

Abstract

Otolith microstructure was examined in juvenile tropical herbivorous fish belonging to the families Acanthuridae and Saridae at Lizard Island. Growth increments on the lapilli of 14 species were validated by tetracycline marking in the laboratory. All species examined deposited growth increments on a daily basis. Increment counts in left and right lapilli were compared for consistency in increment deposition. Interobserver differences were examined as a possible cause of bias in age estimates for Ctenochaetus binotatus and Scarus schlegeli. Given the precision of otolith increment counts by an observer, the differences between counts of the left and right otoliths were acceptable, as were differences between independent observers reading the same otoliths.