Stock Assessment of Atherina Boyeri Risso, 1810 Using Two Different Methodological Approaches (length-based VPA and Catch-only CMSY), in a Freshwater Ecosystem

In this study, stock of the Atherina boyeri Risso, 1810 in habit Iznik Lake was assessed using two different methodological approaches (length-based VPA and catch-only CMSY). A special rigged beach seine (with 6 mm codend mesh size) was used in the sampling process. Fishing trials were carried out 4 different stations of lake between March-2014 and February-2015 with monthly period so as to generating of the length frequency (LFQ) data. TropFishR package was used for analyzing of the LFQ data with bootstrapped ELEFAN I process in the VPA. A total of 2938 fish were measured in the study. A 21-year-old official catch data was used in CMSY analysis. Growth parameters L-infinity, K, and t(o) were estimated as 14.21 cm, 0.52 yr(-), -0.3 for female; 13.82 cm, 0.55 yr(-), -0.37 for male and 14.26 cm, 0.52 yr(-), -0.39 for both sexes respectively. Total mortality coefficient (Z), natural mortality (M) and fishing mortality (F) were estimated as 3.57 yr(-), 1.04 yr(-) and 2.53 yr(-) respectively. VPA based biological reference points F-max, F-05, F-01, and SPR were estimated as 1.09, 0.48, 0.67 and 0.11 respectively. CMSY based reference points F-MSY, MSY, B-MSY, F were computed as 0.382, 1.987, 5.079 and 0.511 respectively. Overexploitation was determined on the A. boyeri stock using of the both VPA (F/F-max > 1) and CMSY (F/F-MSY > 1). Fishing pressure should be decrease for sustainability of the A. boyeri's stock in Iznik Lake.