Population dynamics and fisheries management of Gilthead sea bream, Sparus aurata (f. Sparidae) from Bardawil lagoon, North Sinai, Egypt

Abstract

opulation dynamics of Gilthead sea bream, Sparus aurata was studied from a small scale fishery of Bardawil lagoon. 3262 specimens ranged between 11 and 32.9 cm TL and 20 to 592 g total weight, were collected from April, 2009 to November, 2010. The relationship between length and weight was estimated as W = 0.025 L 2.813. Age was determined using scales' reading technique for 865 individuals and the longevity of this species was found to be 4 years. Growth in length and weight at the end of each year was estimated. The growth parameters of the von Bertalanffy equation were calculated as L ∞ = 36 cm, K = 0.39 yr-1 and t 0 =-1.68 yr. Total, natural and fishing mortality rates were 1.02 yr −1 , 0.21 yr −1 and 0.81 yr −1 , respectively. The current exploitation rate (E = 0.79) indicates that the stock of seabrea in Bardawil lagoon was heavily exploited. The length at first capture L c was estimated as 15.54 cm. The length at first maturity L m of males and females were estimated as 20.5 and 22.8, respectively. The maximum allowable limit of exploitation (E max) was 0.61 while that at maximum economic yield (E 0.1) was 0.499 and maintains 50% of stock (E 0.5 = 0.37). The raised L c to the first sexual maturity (22.5 cm as Lt) would be associated with an increase of Y′/R by 15 % from the current Y′/R at exploitation rates equal E max = 0.74. Also, raised L c to 24.5 cm at current exploitation rate E max =0.79. The results indicate that, for proper management of sea bream catch on Bardawil lagoon, the effort should be reduced or the length at first capture should be raised.