AGE AND GROWTH OF THE RED STEENBRAS PETRUS-RUPESTRIS (PISCES, SPARIDAE) ON THE SOUTH-EAST COAST OF SOUTH-AFRICA

Sectioned sagittal otoliths were used for age determination of red steenbras. The growth zones were composed of opaque and translucent zones. The otoliths were viewed burnt and unburnt, the former giving slightly clearer zone patterns under reflected light. The otoliths have a crenulated edge and exhibit stacking of growth zones, which prevented accurate measurement of zone growth and back-calculation of age. Seasonality of zone formation was not determined because interpretation of the crenulated margin was difficult. Data analysis included down-weighting age-length points for which the age estimates were determined imprecisely. Von Bertalanffy and Schnute growth models were fitted to the data. The best fit to the whole data set was obtained with the Schnute model. Differences in growth between males and females were not statistically significant, possibly because of the poor precision of the fit to the data set for females. Red steenbras live to at least 33 years and attain sexual maturity at approximately 7,2 years. Per-recruit analysis suggests that they are highly susceptible to overfishing, particularly because juveniles are effectively unprotected by current minimum size regulations. The consequences of this include the possibility of growth- and recruitment-overfishing.