Seasonal Changes in Population Parameters and Mortality Rates of the Red Mullet (Mullus barbatus L., 1758) in the South-Eastern Part of the Black Sea Coast of Turkey

Abstract

The red mullet (Mullus barbatus L., 1758) is one of the most abundant species in the coastal waters of Turkey. Population parameters of the red mullet were studied using 1845 specimens caught from Ordu Coast of the southern Black Sea, Turkey, with gill nets between October 2017 and September 2018. Monthly variations in GSI and HSI were observed and the highest values for these physiological indices were recorded in May 2018. The highest condition factor (K value) was found in July 2018. Maximum ages were determined as 4 years for females and 3 years for males. Mean lengths and weights for females and males were measured as 14.0 +/- 1.66 cm; 30.5 +/- 13.09 g and 13.1 +/- 1.23 cm, 24.2 +/- 8.04 g, respectively. Average length and weight were 13.7 +/- 1.56 cm and 28.0 +/- 11.79 g, respectively. However, females appeared to be bigger in length compared to their male conspecifics, the length-weight relationship was sex-independent. The length-weight relationship equation for all individuals was W = 0.0058L(3.23). The von Bertalanffy growth equation was derived as L-t = 22.05(1 - e(-0.43(t + 0.415))) for females, L-t = 22.05(1 - e(-0.33(t + 0.547))) for males and L-t = 17.85 (1 - e(-0.89(t + 0.207))) for all individuals. Instantaneous total mortality, natural mortality and fishing mortality rates were calculated as Z = 1.57 year(-1), M = 0.87 year(-1), and F = 0.70 year(-1). Exploitation rate was E = 0.45, suggesting E = 0.50.