Preliminary evaluation of by-catch, mortality and yield per recruit for the Sea bass, Dicentrarchus labrax in hand line fisheries, Bardawill Lagoon, North Sinai, Egypt

Hand line gear is the main fishing method used that target sea bass in Bardawill lagoon. The present study was carried out in the lagoon from May to December, 2016 in order to evaluate the by-catch, mortality and yield per recruit. Samples were collected biweekly from three vessels equipped by three lines have live bait. Length at first maturity (L_m50) was estimated. Fish below L_m50 was accounted as a by-catch. Adult and by-catch were recorded as numbers and biomass (kg) per units. By-catch was calculated monthly. Growth parameters, mortality and yield per recruit were determined. The length at first maturity (L_m50) was estimated as 32.5 cm (TL), which corresponding to the second year of life. 40.8% of the Sea bass catch per unit was recorded as a mature fish versus 59.2% as immature ones (by-catch). By-catches are predominant throughout the fishing season except from August to October. Growth parameters; L∞ and K were estimated at 47.25 cm and 0.27 per year respectively. The current exploitation rate (E) was estimated at 0.68 and the total mortality (Z) was 0.83 yr^-1. The length at first capture (L_c50) was estimated at 24.5 cm. Relative yield per recruit was 0.68, 0.6 and 0.37 at the maximum (E_max), economic (E_0.1) and optimum exploitation (E_0.5) respectively. The study recommended that the hook sizes should be increased to capture the mature size ratio L_m/L_∞ = 0.65. Fishing from August to October is preferred by hand line gear and prevents at the rest of the fishing season. Exploitation rate should be reduced by 50%.