Age, growth and reproduction of the white seabreamDiplodus sargus sargus(Linneaus, 1758) off the eastern coast of Algeria

Abstract

Summary The objective of this study was to determine the basic population-specific parameters necessary for fish stock assessment in the area and to compare these with data from other Mediterranean regions. White seabream Diplodus sargus sargus (n = 449) were caught along the Algerian coast between December 2005 and December 2006. Total length ranged from 12.2 to 34.6 cm, representing age classes between 0 and 10 years. Validity of the otolith readings for estimating age and growth was supported using the back-calculation method. The von Bertalanffy growth parameters for all fish were calculated as: TL = 36.3 cm, k = 0.154 year−1, t0 = −0.488 year. The growth performance index (φ) showed a relatively slow growth of the local population. The length-weight relationship showed an isometric growth (b = 2.98; r = 0.98). Subspecies Diplodus sargus sargus was characterized as being a proterandric hermaphrodite. Overall ratio of males to females was 1 : 1.4, with males predominant in the smaller size intervals and females in the larger ones. The reproductive season extended from January to May, with a March–April peak in spawning activity. Fifty per cent maturity of the tested cohort was reached at a total length of 20.2 cm for males and 20.0 cm for females.