Estimating some population parameters of gilthead seabream, (Sparus aurata l., 1758) in the Beymelek lagoon lake

In this study, length-weight compositions and relationships, age compositions, growth parameters, mortality rates, and population size estimation of gilthead seabream, (Sparus aurata L., 1758) using different fishing methods were investigated between October 2006 and May 2007 in the Beymelek Lagoon Lake. To estimate the parameters, length-weight measurements, age estimations from scales and tagging methods were used.A total of 58790 individual, 51707 individual from commercial fisheries and 7083 individual from fishing trap were captured during the fishing season of 2006-2007. For gilthead seabream obtained from the commercial fisheries, length range was between 17.8 and 37.5 cm and weight range was between 81 and 768 g, whereas for the gilthead seabream from the fishing trap, length between 17.8 and 42.2 cm and weight between 73 and 1206 g. Ages of gilthead seabream, determined from scales, 0 to V, varied from years, while most of the estimates were in the age groups of I, II, and III years.A total of 400 individual of gilthead seabream were tagged to estimate growth parameters and population size by marking. A total of 65 (16.25%) recaptures were obtained from both the commercial fisheries (44 individuals) and fishing traps (21 individuals).Von Bertalanffy Growth parameters were estimated as L? = 33.42 cm, K = 0.474, t0 = -0.3347 using Gulland-Holt method with tagged dates and as L? = 61.66 cm, K = 0.146, t0 = -1.6995 using Ford-Walford method with age determination. Growth performance indexes obtained from tagged and age determination were estimated as 6.272 and 6.319, respectively.Instantaneous mortality rate was estimated as 0.454 (survival rate 63.5%) from the tag dates, as 0.856 (survival rate 42.49%) from length composition dates using Beverton?Holt method, as 0.801 (survival rate 44.90%) from catch curve method, and as 0.788 (survival rate 45.46%) from length dates. Natural mortality rate using recaptured and Von Bertalanffy Growth parameters were estimated as 0.38 and 0.26, respectively.Using the tag-recapture data, the population size of gilthead seabream was estimated as 357200 individuals in the Beymelek Lagoon Lake.