Original Articles

Validation of age estimates in sparid fish using flubrochrome marking

Published in: South African Journal of Marine Science
Volume 13, issue 1, 1993 , pages: 195–203
DOI: 10.2989/025776193784287284


The marking of sparid otoliths by means of oxytetracycline and alizarin complexone was investigated by immersion, feeding and intraperitoneal and intramuscular injections. Of these techniques, immersion for 24 h in a 100–150 mg·ℓ−1 seawater solution of alizarin complexone was found to be most suitable for marking larval and small juvenile fish. Intramuscular injections of oxytetracycline at a dosage of 250 mg·kg fish−1 was the most suitable method for marking the otoliths of juveniles in the laboratory, while dosages between 50 and 100 mg·kg fish−1 were used to mark adults in the field. Feeding labelled food to the fish and intraperitoneal injections did not produce a clear mark in the otolith. Fluorochrome marks confirmed the daily periodicity of micro-increment formation in some captive sparid species (Diplodus sargus and D. cervinus), and field experiments using Chrysoblephus laticeps showed that this method was a relatively simple way of directly validating age estimates in sparid fish.

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