Validation of otolith growth-increment periodicity in tropical gobies

We assessed the efficacy of tetracycline, calcein and strontium chloride fo r validating the periodicity of otolith growth-increments in eight species of tropical marine gobies (family Gobiidae). We compared the number of fish es in which the otoliths were successfully marked when each of these chemic als was administered by intraperitoneal injection or immersion bath at a ra nge of doses and immersion times. All three chemicals could produce a detec table mark in the otoliths of five reef-flat gobies, Asterropteryx semipunc tatus, Amblygobius bynoensis, Istigobius goldmanni, Valenciennea muralis an d Amblygobius phalaena; however, tetracycline injection at 50 mg kg(-1) is recommended because it produced a brighter otolith mark than calcein and is cheaper and quicker to detect than strontium chloride. Calcein immersion t reatment of 125 mg 1(-1) for 24 h was the most successful treatment for two estuarine gobiids, Favoni-gobius reichei and Glossogobius biocellatus. No treatment produced a detectable mark in the otoliths of the coral-dwelling goby Gobiodon histrio. Adequate care in the preparation of otoliths was fou nd to be essential for detection of the validation mark produced by tetracy cline and calcein. Otolith growth-increments were deposited daily in the se ven species of goby for which validation was possible.