Population Structures of the Two Banded Seabream, Diplodus vulgaris and the White Seabream, Diplodus sargus Reveal New Records in Maximal Age

The common two-banded seabream Diplodus vulgaris and Diplodus sargus were sampled from non-commercial fishing catches around the Maltese Islands between July 2012 and December 2017. A total of 1550 (D. vulgaris N=1204, D. sargus N=346) specimens were collected. In this study, age, growth, length-weight relationship (LWR), condition factor (K) and relative condition factor (Kn) were investigated. Ages ranged from 0 to 17 years for D. sargus and 0 to 16 years for D. vulgaris. A positive allometric growth was observed for D. sargus while growth in D. vulgaris was isometric. Average Kn was found to be 0.99 and 1.01 in D. vulgaris and 0.97 and 1.00 in D. sargus for males and females respectively. The growth parameters of the von Bertalanffy equation were: L∞=26.71 and 30.86 cm, K= 0.275 and 0.286 year-1 and tₒ = -2.27 and -1.61 year for all individuals of D. vulgaris and D. sargus respectively. This study is the first reference on the LWR equation parameters, Kn, K and Age for these species around the Maltese Islands and establishes a new maximum age for D. vulgaris of 16 years.