Population Dynamics, Current Trends and Future Prospects of the Black Goby (Gobius niger) in the Eastern Part of the Black Sea (Turkiye)

Abstract

With its adaptation to the Black Sea, the black goby Gobius niger (Linnaeus, 1758) has increased in biological and ecological importance in recent years. Despite previous studies, up-to-date information on population status in the Black Sea is still lacking. Specimens were collected monthly from April 2020 to March 2021 from different commercial fishing landings on the Turkish coast of the eastern Black Sea. The total length of sampled individuals (n=630) ranged from 7.20 to 14.0 cm. Males were dominant throughout all size classes and the overall sex ratio was significantly different from the expected ratio of 1:1. The length-weight relationship indicated isometric growth (b=3) for both sexes. Spawning occurred from March to June. The observed maximum age was 4 and both males and females were dominant in age group 3. The black goby appeared to have relatively low growth rates (Φ′=1.74) in the Black Sea, but longer asymptotic length (L∞=16.94 cm) data were obtained in the study area. The total mortality rate (Z) estimated by means of the catch curve method was 1.43 yr-1 and the fishing mortality (F) was 0.88 yr-1. The estimated exploitation rate (E) was 0.61 yr-1 which was higher than the optimum value of 0.5. Updated biological parameter estimates show that black goby populations in the Black Sea are now more exploited than previously thought. Additional studies are recommended to ensure sustainable management of black goby populations and national regulations to reduce bycatch.