Preliminary notes on the formation of daily increments in otoliths of Oreochromis aureus

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Abstract
Daily growth increments were studied in otoliths of early stage Oreochromis aureus (Cichlidae, Teleostei). A laboratory experiment was carried out on the effect of temperature and food ratio on the otolith growth of juvenile fish. Juvenile O. aureus were reared at two different temperatures, 17.degree.C and 28.degree.C respectively. The young fish were fed two different ratios Trouvit beginning with the first day of swimming and external feeding. Samples were taken at random from each group an dthe sagitta otoliths were examined. Otolith growth was linearly related to somatic growth of individual fish. Otolith microstructure analysis showed that increment formation began two or three days prior to the transition to the free-swimming stage and continued thereafter following a daily pattern. Temperature and food ratios had a direct influence on the increments widths of the otoliths.