Age, growth and mortality of blotched picarel Spicara maena L. (Pisces: Centracanthidae) in the eastern central Adriatic

Abstract

Age, growth and mortality of the blotched picarel, Spicara maena (L., 1758), were determined from specimens ( N=1130) collected on the eastern central coast of the Adriatic Sea from 16 September to 10 October 1996. Total length ranged from 7.8 to 27.5 cm, while weight varied between 5.2 and 298.0 g. The von Bertalanffy growth equation was fitted on the basis of mean length-at-age data resulting in parameter values of L ∞=24.82 (S.E.=0.469), K=0.532 (S.E.=0.0302), and t 0=−0.089 (S.E.=0.0321) ( R=0.9985). Weight growth constants were: W ∞=211.17 (S.E.=14.843), K=0.504 (S.E.=0.0424), and t 0=0.099 (S.E.=0.0.076) ( R=0.9627). Weight increased allometrically for both sexes together with b=3.12 (S.E.=0.025). The blotched picarel is a relatively long-lived species. The oldest male and female were estimated to be 8 and 3 years old, respectively. Total ( Z) and natural ( M) mortality were 1.18 and 0.98 per year, respectively. The exploitation ratio E=0.17 revealed an underfished stock. The sex ratio was skewed in favour of males (1.41:1). Sex reversal was mainly observed between 17.5 and 18.0 cm. Females were observed up to a total length of 19.8 cm.