Population dynamics and stock assessment of two mullet species (Chelon auratus Risso, 1810 and Mugil cephalus Linneaus, 1758) in the Köyceğiz lagoon-estuary (Mediterranean coast)

Abstract

In this study, the populations and stocks of Chelon auratus and Mugil cephalus in the Köyceğiz Lagoon (Mediterranean coast) were investigated. The length–weight relationships, growth performances (φ) and growth coefficients (K) of C. auratus and M. cephalus were determined to be W = 0.0075L2.9744 and W = 0.0041L3.22025, 2.73 and 2.79, 0.185 and 0.230, respectively. C. auratus and M. cephalus had respective total, natural and fishing mortality rates of 1.52 and 1.25, 0.41 and 0.47, and 1.11 and 0.78. The Z/K ratio of C. auratus and M. cephalus was estimated as 2.505 and 1.890, respectively. The recruitment period fluctuated throughout the year for C. auratus, with a peak of 21.6%, a lower level of 13.85% in October and a minimum of 1.85% in January, while the recruitment process of M. cephalus peaked at 3 during the spring. Recruitment peaked from February to April followed by a second peak in September, and fluctuated throughout the year. The recruitment period fluctuated throughout the year for C. auratus, with a peak of 21.6%, a lower level of 13.85% in October and a minimum of 1.85% in January, while the recruitment process of M. cephalus peaked at 3 during the spring, with a steady peak from February to April, followed by a second peak in September, and fluctuated throughout the year. C. auratus and M. cephalus E0.1, E0.5, and Emax values were estimated to be 0.714 and 0.575, 0.371 and 0.379, and 0.852 and 0.875, respectively. The maximum sustainable yields (MSY) of C. auratus and M. cephalus were estimated at 151.24 and 249.31 tonnes, respectively. It has been concluded that the stocks of C. auratus and M. cephalus (especially C. autratus) in the Köyceğiz Lagoon (Mediterranean coast) are overexploited.