Length-weight relationships, growth parameters, mortality and condition factor of Atlantic bonito (Sarda sarda Bloch, 1793) from the Southern Black Sea

The small tuna known as the Atlantic bonito (Sarda sarda) is one of the most important fishery species on the Black Sea coast of Türkiye. In this study, we sought to define some population parameters of Atlantic bonito based on indirect ageing using length frequency distributions. The aim of this study is to provide data that will serve the management of the bonito fishery. For analysis, the ELEFAN routine in the LFDA and FiSAT programs was utilized. During the migration period, we collected 2110 samples from purse seine (n=1009), gillnet (n=867) and hand lines (n=234) fishing in the Black Sea waters of Türkiye. The fork length varied between 13.1 and 60 cm, and the female-to-male ratio was 1:0.79. The length-weight relationships (LWRs) were calculated W=0.0037FL3.3784 and Fulton’s K:1.01±0.001. The growth was found to be positive allometric (Student’s t-test, p < 0.05). von Bertalanffy Growth Parameters (VBGP) were computed as L∞:71.59 cm, K:0.56 year-1, t0:-0.18 year. The seasonal oscillation in growth rate was calculated (C: 0.98) and winter point (WP): 0.54, growth performance index of Ø’: 3.46, natural mortality (M: 0.74 yr-1), fishing mortality (F: 2.81 yr-1), total mortality (Z: 3.55 yr-1) and exploitation coefficient (E: 0.79 yr-1). As a result, the exploitation rate of S. sarda in the study area was found to be high.