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 biologicalandecologicalimportanceinrecentyears.Despitepreviousstudies,up-to-dateinformation 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 growthrates(Φ′=1.74)intheBlackSea,butlongerasymptoticlength(L∞=16.94cm)datawereobtainedinthestudyarea.Thetotalmortalityrate(Z)estimatedbymeansofthecatchcurvemethod was 1.43 yr-1 and the fishing mortality (F) was 0.88 yr-1. The estimated exploitation rate (E) was0.61yr-1whichwashigherthantheoptimumvalueof0.5.UpdatedbiologicalparameterestimatesshowthatblackgobypopulationsintheBlackSeaarenowmoreexploitedthanpreviouslythought.Additionalstudiesarerecommendedtoensuresustainablemanagementofblack goby populations and national regulations to reduce bycatch.

Keywords

• sex ratio
• age
• growth
• mortality
• fisheries management
• black gob