Turbot, Scophthalmus maximus, is a commercially important demersal flatfish species distributed throughout the Black Sea. Several studies performed locally with a limited number of specimens using both mitochondrial DNA (mtDNA) and microsatellite markers evidenced notable genetic variation among populations. However, comprehensive population genetic studies are required to help management of the species in the Black Sea. In the present study eight microsatellite loci were used to resolve the population structure of 414 turbot samples collected from 12 sites across the Black Sea. Moreover, two mtDNA genes, COI and Cyt-b, were used for taxonomic identification. Microsatellite markers of Smax-04 and B12-I GT14 were excluded from analysis due to scoring issues. Data analysis was performed with the remaining six loci. Loci were highly polymorphic (average of 17.8 alleles per locus), indicating high genetic variability. Locus 3/20CA17, with high null allele frequency (>30%), significantly deviated from HW equilibrium. Pairwise comparison of the F ST index showed significant differences between most of the surveyed sampling sites (P < 0.01). Cluster analysis evidenced the presence of three genetic groups among sampling sites. Significant genetic differentiation between Northern (Sea of Azov and Crimea) and Southern (Turkish Black Sea Coast) Black Sea sampling sites were detected. The Mantel test supported an isolation by distance model of population structure. These findings are vital for long-term sustainable management of the species and development of conservation programs. Moreover, generated mtDNA sequences would be useful for the establishment of a database for S. maximus.

In this study, the structure of the anchovy population in the Azov, Marmara and Black Sea was determined by restriction fragment length polymorphism (RFLP). Sampling was carried out at six stations represented the Azov, Marmara and Black Sea populations in 2011. Total DNA of the sample was taken each station and the mtDNA D-loop region within total DNA was amplified by PCR. Amplified mtDNA D-loop region by PCR (polymerase chain reaction) was cut by10 different enzymes (Hpa

In this study, reproductive performances of F5 and F6 generation hatchery-originated female Black Sea salmon (Salmo labrax) were evaluated to determine the effects of the ongoing selective breeding program. The study was conducted in freshwater pools and marine cage systems between 2018 and 2021. For the study, 53 specimens from F5 generation females with an average length of 52.71±7.08 cm and weight of 1561.29±639.76 gr, and also 56 broodstıcks specimens from F6 generation females with an average length of 51.92±5.35 cm and weight of 1506.12±417.28 gr were used. Gonad maturity controls and spawning studies were carried out in the 2018-2019, 2019-2020 and 2020-2021 breeding periods along the entire season, lasting from November to January. The number of ovulating females, their fecundity, egg diameters and fertilisation rates of eggs were recorded. In all seasons, 36.17% of F5 females ovulated in November, and the remaining females (63.83%) ovulated in December. Ovulation time in F6 females also showed a similar pattern of 1/3 of females (37.40%) ovulating in November and the remaining majority (62.60%) ovulating in December. According to the results, total egg yields as 4439.31±1675.69 and 4112.08±1041.16 egg/broodstock, relative egg yields as 2313.44±278.48 and 2345.76±516.30 egg/kg, egg diameters as 5.08±0.19 and 5.21±0.17 mm, and fertilisation rates as 96.78±3.24% and 96.63±3.73% were determined for F5 and F6 generations, respectively. In both generations, as the size of the broodstock increases, the total egg production increases (F5: r=0.9169, F6: r=0.74254), while the relative egg production (F5: r=-0.2526, F6: r=-0.3486) decreases. When the total egg yields and fertilisation rates were compared, the difference between the F5 and F6 groups was insignificant (p≤0.05). The condition factors of the two generations were found to be statistically similar (p≤0.05).

Triploid fish production has become important in the aquaculture sector, especially in the culturing and breeding of the big sized Salmonid species. Black Sea trout (Salmo labrax) is one of the promising Salmonid species for these purposes considering increased demand for this species in the aquaculture sector. In this research, triploid Black Sea trout were treated with heat shocks during reproduction and triploidy of obtained trouts were identified with different techniques. For this reason, heat shocks were applied at 26.5°C, 28°C and 36°C temperatures for 10 minutes during 30 th minute of fertilization and triploidy was determined with fragment analysis, flow cytometry and classic hematological methods. Results indicate that all three temperatures were suitable for the successful reproduction of Black Sea trout. However, 26.5°C gives better results considering both the triploidy success and survival rates. Besides, all three determination techniques especially erythrocyte size measurements and flow cytometry can be used in evaluating of triploidy in Black Sea trout with precise results.

In this study sperm characteristics (sperm volume, sperm volume per kg fish, spermatocrit, sperm concentration, pH, and sperm motility) of wild-caught and hatcheryreared turbot (Scophthalmus maximus), originated from the Black Sea population, were assessed. In this regard, two different trials were conducted. On the Trial-I, sperm characteristics of wild-caught and hatchery-reared turbot (4-, 7-, and 10-year-old) were comparatively investigated during the spawning season (May), on the Trial-II, monthly variations of sperm characteristics of hatchery-reared turbot (4-year-old) were investigated. On the Trial-I, a positive correlation between body weight and sperm volume was recorded. Significant differences were noted in sperm volume, and sperm concentration, however, there was no significant difference between the groups in terms of sperm volume per kg of body weight, spermatocrit, and pH. The sperm motility showed a significant decrease after the 15 minutes post-activation in all the specimens. The active spermatozoa rate of the wild-caught turbot was 44% at 15 minutes post-activation, whereas it was 16%, 13%, and 64% for 4-, 7-, and 10-year-old turbot, respectively. The average motility duration of the wild-caught turbot spermatozoa was significantly longer compared to hatchery-reared turbot despite having a comparatively lower initial motility rate than hatchery-reared turbot.On Trial-II spermiation duration of hatchery reared Black Sea turbot was determined as 6 months, starting from February until the end of July. The highest and the lowest sperm volume, and sperm volume per kg were recorded in June and July, respectively. Significant differences were determined between the months in terms of sperm volume per kg, sperm volume, spermatocrit, and sperm concentration, however, the pH was similar. These results demonstrate the sperm characteristics of wild-caught and hatchery-reared Black Sea turbot were different in the spawning season (May) and the potential spermiation season was between February and July.