Validation of Annular Deposition in Scales and Otoliths of Flathead Mullet Mugil cephalus

Chih-Chieh Hsu and Wann-Nian Tzeng (2009) Validation of annular deposition in scales and otoliths of flathead mullet Mugil cephalus. Zoological Studies 48(5): 640-648. Age estimation of fish is essential for understanding their life history and population dynamics, and for assessing and managing stocks. The periodicity of age marks of both scales and otoliths of flathead mullet Mugil cephalus was validated using cultured fish of known ages, and these were compared to those of wild ones. Annuli in scales were characterized by dense circuli in the basal area, merged circuli in the lateral-basal area, and interrupted circuli in the lateral area of the scale. Annuli in whole otoliths were characterized by an opaque zone under both reflected and transmitted light. In acid-etched sectioned otoliths, annuli were defined by dense concentric rings. Annuli of both scales and otoliths of M. cephalus were coincident and were deposited once a year during winter. Scales are convenient for age estimation because there is no need for special treatment. Preparing otolith sections for etching is time-consuming and costly, but the otolith microstructure and microchemical analyses can provide additional life-history information. http://zoolstud.sinica.edu.tw/Journals/48.5/640.pdf