Sexual seasonal growth and mortality of Scaldback, Arnoglossus kessleri Schmidt, 1915 (Pleuronectiformes: Bothidae), caught by experimental beam trawl in the Black Sea, Turkiye

The scaldback, Arnoglossus kessleri, is a small fish that belongs to the Bothidae family and its biology is unknown in the Mediterranean Sea including Aegean Sea, Black Sea and Sea of Marmara. To describe first information on the seasonal von Bertalanffy growth function parameters (SVBGF) using length frequency data for A. kessleri, and also to present first information on indirect methods to estimate natural (M) and total mortality rates (Z), a total of 12 months samplings were conducted between December 2012 and November 2013 in the south-east Black Sea. The overall sex ratio of females: males skewed towards males (χ2, P < 0.01). The SVBGF parameters, computed from monthly length frequency distribution analysis (LFDA), were estimated as L∞ = 8.25 cm total length (TL), K = 0. 549 year-1 for females and as L∞ = 8.44 cm TL, K = 0.490 year-1 for males. The seasonal oscillation in growth rate for females (C = 0.340) was larger than it was for males (C = 0.260). The slowest period of growth corresponded to December both females and males. The seasonal growth of the scaldback was most probably initiated by photoperiod and accelerated with decreasing water temperatures. Total instantaneous mortality rate, Z, was estimated as 0.853 yr-1 for females and 0.774 yr-1 for males. Instantaneous natural mortality ratio, M, was estimated a bit higher for females (M = 0.714±0.129) than for males (M = 0.655±0.098). The exploitation rate, E, of both sexes was also lower than the optimum exploitation (E = 0.5) criterion, which is indicative of non-exploited and/or lightly exploited of A. kessleri population. The results of this study were offered as biological input parameters for management of Black Sea stocks of the scaldback species.

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