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The European grayling, Thymallus thymallus (L.), is one of the most important, valuable commercial fish species in Poland. Three basic parameters describing angling pressure on this fish in the Dunajec River catchment were analyzed: mean monthly catch per angler, total catch per anglers belonging to the various branches of the Polish Anglers Association, and total catch per angling district. It was found that a total of 74 014 grayling specimens (weighing 25 511.1 kg) were caught in the Dunajec catchment in the period of 1999-2011. In the beginning, annual catch increased rapidly, with the maximum in 2002, when 20 796 specimens weighing 6810.2 kg were taken by anglers. Since then, the catch has decreased gradually. In 2004, the number of grayling harvested decreased by 66.3 %, and in the following year an additional 52 % decrease was observed. Despite conservation measures undertaken by the Polish Anglers Association, catches continued to decrease in subsequent years. The results presented, along with considerations on the origin of stocking material released in the Dunajec catchment, suggest a serious disruption in the phylogenetic integrity of the populations of the gray ling in this river system might have occurred, resulting in the decline in recreational catches. It is recommended that the the stocking material released into the Dunajec River catchment is of high quality and phylogeographic unity; otherwise, the conservation of the European grayling could be wholly unsuccessful.
Spermatozoa quality of two grayling (Thymallus thymallus L.) populations: free-living and bred in ponds, was compared. The percentage of spermatozoa activated upon contact with water, time of progressive movement (turbulent and smooth phase), time of oscillatory movement and the spermatocrit were determined. Males living in a river, as compared with those reared in a pond, displayed a significantly higher percentage of activated spermatozoa, whereas both populations did not significantly differ in spermatozoa motility and spermatocrit.
Nucleotide sequences of the partial mitochondrial DNA (mtDNA) control region and flanking tRNA Phe gene (a total of 150bp) were determined in eight specimens of European grayling, Thymallus thymallus, representing five rivers in southwestern Poland. Two haplotypes, A and B, were identified which differed from each other by two nucleotide substitutions. Haplotype A was detected in fish from two rivers, the Zadrna and Bóbr, whereas haplotype B was detected in fish from three others, the Widna, Biala Gluchołazka and Metuja. The different phylogenetic position of the mtDNA haplotypes observed in samples from rivers which are in close proximity may suggest genetic structuring of grayling populations in the region, but further sampling is required to test this hypothesis.
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