Length-weight relationship and population parameters of the sea bream, Sparus aurata (Linnaeus, 1758) in Abu Qir Bay, Mediterranean Sea, Egypt

The present work aimed to study some biological and population parameters of Sparus aurata in Abu Qir Bay, Alexandria to understand the status of its stock and give essential information to assess proper management for this species in the bay. A total of 1029 random specimens of gilt-head sea bream, S. aurata were monthly collected from commercial catch in the landing site at Abu Qir Bay during the period from January 2020 to January 2021.  For each fish sample, total length (cm) and total weight (g) were measured, and scales were used for age determination. The total scales’ radius and the radius of each annulus were calculated to the nearest 0.01 cm.  The back-calculation method was used to estimate growth in length and weight at the end of each year. Results of the length-weight relationship showed that the growth of S. aurata in Abu Qir Bay fishery is nearly isometric (b: 3.01). The longevity of  S. aurata was more than 5 years. The maximum increment of the linear growth occurred by the end of the first year of life (15.61 cm), but the maximum value of increment in weight (69.95 g) was recorded at age group IV⁺. Age groups I⁺ and  II⁺ were the most abundant amounting 55.6% of its total catch.  The length at first capture (Lc)was 18.96 cm. Total, natural and fishing mortality rates for S. aurata were 1.16 yr^-1, 0.56 yr⁻¹ and 0.60 year⁻¹, respectively. Growth parameters were calculated as L∞ = 35.49 cm, K = 0.25 yr-1 and t₀ = -1.27 yr.  Exploitation rate (E = 0.52) indicates that the stock of sea bream was  slightly higher than that optimally exploited stock.