Population genetic structure of turbot (Scophthalmus maximus L., 1758) in the Black Sea

Abstract

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.

Genetic diversity and morphological characterisation of three turbot (Scophthalmus maximus L., 1758) populations along the Bulgarian Black Sea coast

“…On the whole, the allelic diversity (mean number of observed alleles per locus) for populations along the Bulgarian Black Sea coast (3.559) is higher than that reported by Bessonova and Nebesikhina (2019) for the same loci in turbot populations from the Crimean Black Sea (3.430) and Azov Sea (3.420) and lower than species from the Caucasian Black Sea coast (3.623). The mean values for the obtained and expected heterozygosity (Ho = 0.638 and He = 0.685) are close to those indicated by previous studies for the same loci in turbot populations (Estoup et al 1998;Iyengar et al 2000;Bouza et al 2002;Bessonova and Nebesikhina 2019;Turan et al 2019b;Firidin et al 2020). The relatively high heterozygosity and allelic diversity of these populations suggest that local gene flow takes place amongst them.…”

“…The studies of the turbot populations, characterised by genetic diversity parameters (PIC and I), indicate that these values were high for six of the loci analysed (PIC and I higher than 0.6 and 1.3, respectively) indicating, thereby, high genetic diversity (Froufe et al 2004;Fopp-Bayat 2010) (Table 3). The PIC values from each loci varies between populations analysed (0.622-0.825) and were comparable with the data for turbot population from the Black Sea (0.713-0.853) (Firidin et al 2020) and from Turkey, France and South Korea (PIC 0.3-0.9) (Han et al 2018) indicating the random loci were under independent selection pressure and seem to be ideal to be used as a divergence index. For detection of the bottleneck events, the Garza-Williamson index (M) was successfully employed.…”

“…The Shabla, Nesebar and Shkorpilovtsi populations had the smallest number of alleles per Smax-02 locus in comparison with all Black Sea populations previously investigated (Table 2). For the other loci, the data obtained were similar (Turan et al 2019b;Bessonova and Nebesikhina 2019;Firidin et al 2020). The most polymorphic locus in the current study was Sma-USC26 in the Shabla population (Table 2).…”

“…Molecular markers (microsatellites and mtDNA) were applied only to closely-related turbot species in different marine regions in order to assess the genetic diversity (Bouza et al 2002;Suzuki et al 2004;Vandamme et al 2014Vandamme et al , 2020do Prado et al 2018). Thus, using these molecular markers, limited data on the population structure of S. maximus in the Black Sea were obtained (Atanassov et al 2011;Nikolov et al 2015;Bessonova and Nebesikhina 2019;Turan et al 2019b;Firidin et al 2020;Ivanova et al 2020). Accordingly, to avoid depletion of the genetic diversity, fisheries management should be based on a more comprehensive knowledge of the genetic integrity of the populations.…”

A preliminary assessment of metal/metalloid levels in wild and farmed turbot ( Scophthalmus maximus ) and risks imposed on human health

“…Turbot ( Scophthalmus maximus ; synonym, Psetta maeoticus ) is a demersal fish species of the family Scophthalmidae that is widespread in the Black Sea and also cultured worldwide (Firidin et al, 2020; Froese & Pauly, 2018; Nunes et al, 2014). It is a predatory fish species mainly feed on bottom‐living fishes, and to a lesser extent, on crustaceans and bivalves (Froese & Pauly, 2018).…”