Antibiotic resistance and the presence of resistance genes (ARGs) were investigated in the bacteria isolated from rainbow trout (Oncorhynchus mykiss) from different trout farms located in Turkey. The most frequent types of antibiotic resistance were towards β‐lactams (cephalothin [70% of bacterial isolates], amoxicillin [63%], ampicillin [62%], ticarcillin [56%], aztreonam [51%]), macrolide [erythromycin, 68%] and sulphonamide [sulphamethoxazole, 51%]. Of bacterial isolates, 51% were multiple drug resistant (MDR), while 35% of the isolates were extensively drug resistant (XDR). None of isolates were pandrug resistant (PDR). The most common ARGs were ampC (36%) and sul1 (24%). The class 1 integron gene cassette was detected in 51% of the bacteria. There was a strong positive correlation between the antibiotic resistance rate and the presence of ARGs (r2 = .932). Gene encodes blaCTX‐M1, one of the extended spectrum beta‐lactamase enzymes, was first described in Aeromonas caviae, Photobacterium damselae, Pseudomonas luteola and Burkholderia cepacia. It was determined that 35% of the bacteria harboured at least one plasmid. Plasmid‐mediated ARGs were identified to be tetracyclines (tetA, tetB, tetC, tetD), sulphonamides (sul1, sul3) and β lactams (ampC, blapse). Thus, results suggest that ARG contamination situation deliberates resistance to tetracycline, aminoglycoside, chloramphenicol and sulphonamide. Therefore, the presence and activity of ARGs in fish and in environmental bacteria may play an important role in the spread of resistance genes among bacteria by transposition or integron gene cassettes.

We tested for reproductive isolation between Salmo trutta abanticus, S.t. labrax, S.t. caspius and S.t. fario by conducting crosses to produce F1 and F2 offspring. We also estimated the extent of genetic divergence between all three entities by examining sequence variation across the coI, d-loop and cytb mitochondrial genes. All of the F1 cross-types were successfully produced. After 2 years of culturing, F2 generation were produced as well. Fertilization, hatching and survival rates and hatching performance of F1 and F2 generations were evaluated. F2 generation had similar performance to their parent. Fertilization, hatching, larval survival rate and hatchery performance of F1 and F2 generation were similar except pure bred F2 S.t. abanticus. Purebred F1 individuals shared similar coloration patterns and spots with their parents but direction of the hybridization appeared to be decisive on morphology of hybrids. Some of the hybrids exhibit different morphological characters than their parents. Based on partial alignments of the three genes, phylogenetic analysis showed that these S. trutta are gathering within the same clade and appeared as monophyletic group. We found that there were some morphologic and genetic variation among S. trutta subspecies but the degree of variation does not warrant species level recognition. These findings indicate that the four subspecies constitute a single biological entity, corresponding to different morphs of the Danubian lineage. We therefore recommend that S. trutta belonging to Danubian lineage in Turkey be referred to as Salmo trutta and that strains be named according to location, such as Abant, Caspian, Black Sea and Anatolian.

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.

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