Age composition, growth, and mortality of European hake Merluccius merluccius (Actinopterygii: Gadiformes: Merlucciidae) from the northern Aegean Sea, Turkey

Abstract

Background. This study is the first attempt to acquire information about growth, age composition, and mortality of European hake, Merluccius merluccius (Linneaus, 1758), in the northern Aegean Sea. In Turkey, the hake is a very important commercial species captured with demersal trawls. Therefore the management of the hake fishery is important for the stock sustainability. The aim of this study was to determine the age composition, growth, and mortality of hake from Gökçeada Island, northern Aegean Sea, Turkey. Materials and methods. A total of 2253 hake specimens were collected monthly in three fishing seasons off Gökçeada Island from September 2013 to April 2016 with a commercial trawler. Fish age was estimated based on otoliths. Growth parameters were calculated according to the von Bertalanffy growth equation. Results. The total length ranged from 5.9 cm to 51.2 cm for all individuals. The length–weight relation was W = 0.0034TL3.2249 (R² = 0.9655). The age of the fish was estimated to range from 1 to 6 years. Growth parameters were as follows, L∞ = 88.54 cm, k = 0.1088, t0 = –0.9962 for males, L∞ = 102.34 cm, k = 0.0908, t0 = –1.3105 for females, and L∞ = 102.66 cm, k = 0.0992, t0 = –0.8085 for all fish sampled. The total, natural, and fishing mortality ratio of the samples were found as 2.21, 0.57, and 1.64, respectively. Conclusion. The exploitation ratio (E) of the samples was estimated to be 0.74, showing a high fishing pressure on the hake population and it will be the main argument for the need of a strict management on the hake fishery in the area studied. The other argument is the high number of juveniles in the catch composition. It is expected that the results of the presently reported study will contribute to the sustainable fishery for hake. The minimum landing size in the Turkish waters should be increased from 20 cm to 25 cm to ensure at least single breeding of Merluccius merluccius.

Keywords

• Merluccius merluccius
• age
• growth
• mortality
• nor