Age determination of black bream, Acanthopagrus butcheri (Sparidae), from the Gippsland Lakes of south-eastern Australia indicates slow growth and episodic recruitment

The age of black bream (Acanthapagrus butcheri) in the Gippsland Lakes of s outh-eastern Australia was estimated with high precision from sectioned oto liths of fish sampled from 1993 to 1996. Ageing techniques were validated b y following the progression of age classes over 4 years. Correct identifica tion of the first increment was aided by reference to the position of the s ubcupular meshwork fibre zone, and age assignment was confirmed by linear r egression analyses of otolith weight against fish age. The growth of black bream was found to be slower, and their natural life span longer, than prev iously estimated from length-frequency distributions and scale readings. Th e maximum age recorded was 29 years, with most black bream 4-9 years old an d few fish more than 10 years old. There were significant differences betwe en the growth rates of males and females. The von Bertalanffy growth parame ters were: L-infinity 54.5 cm FL, t(0) -5.21 years, K 0.042 year(-1) for fe males and L-infinity 38.2 cm FL, t(0) -3.70 years, K 0.077 year(-1) for mal es. The current age structure suggests that recruitment has been episodic s ince 1981 and low for three recent years in succession.