Validation of Daily Growth increments in Otoliths form Thrysa aestuaria (Ogilby), a tropical Anchovy from Northern Australia

Abstract

Age and growth parameters were determined for the tropical anchovy Thryssa aestuaria from northern Queensland, Australia. Larval and juvenile forms of T. aestuaria, believed to be a single cohort recruited in the spring of 1990, were sampled between October 1990 and January 1991. Counts of growth rings in sagittal otoliths were determined for specimens from three of these samples. Comparisons of the different ring counts of fish from successive samples with the number of days elapsed between samples suggested that the growth rings examined were deposited daily. Two specimens of T. aestuaria marked with tetracycline hydrochloride in aquaria were found to deposit growth rings in the sagitta at a rate of one ring per day. Problems associated with reading daily growth rings in tropical anchovies are discussed in light of the results of this study. Growth in T. aestuaria is discussed in relation to reported growth information for other species of tropical anchovies.