Age and growth, maturity, mortality and yield-per-recruit for two banded bream ( Diplodus vulgaris Geoffr.) from the south coast of Portugal

Abstract

The population dynamics parameters of Diplodus vulgaris (Sparidae) from the south and south-west coast of Portugal were studied. 1086 fishes with total lengths ranging from 3.3 to 37.9 cm were obtained from previous gear selectivity studies supplemented by market sampling and beach seining for juveniles (1992–2000). The spawning season extended from September to April and total lengths at 50% maturity were 17.27 cm for males and 17.65 cm for females. These estimated sizes were greater than the minimum legal landing size (MLS=15 cm) and smaller than length at first capture (Lc 50=21.68 cm) for the longline fishery. The parameters of the von Bertalanffy growth equation were: L ∞=27.73 cm, K=0.40 per year, t 0=−0.34 year. The instantaneous rates of total mortality ( Z) and natural mortality ( M) were 0.63 and 0.45 per year, respectively. Rates of fishing mortality F and exploitation E were 0.18 and 0.28 per year, respectively. Estimated parameters and the relative yield-per-recruit analysis showed that this species is not over exploited by longlines.