Republic. Acta vet. Bmo 1995,64: 195-208.Tissues (muscle, kidney, liver, gonads) were investigated for residues of pollutants in wels (Silurus glanis) from 6 large ponds (Bezdrev, Spolsky, Kaclehy, Vrko<:, NovoveskY, Bezruc), from Labe river and from the OrUk reservoir and in brown bullhead (lctalurus nebulosus) from the river Labe. Thirty and 10 individuals of wels were investigated from ponds and the Orlik reservoir, respectively, and 2 individuals from the river Labe. Thirty five individuals of bullhead were investigated from various localities of the Labe. Among pollutants, metals (Hg, Pb, Cd, Cu, Zn, Cr, AI), PCBs as amount of technical mixtures used in .the Czech Republic (Delor 103 and Delor 106) and as 7 indicator congeners (K28, K52, KIOI, K118, K153, K138, KI80), DDT and its metabolities, HCB, HCH isomers, triazines (atrazine, simazine, prometryne, desmetryne, terbutryne) were assessed. The values of individual pollutants found in tissues of wels from ponds were very low and corresponded to hygienic limits in all cases. On the other hand, much higher values of pollutant residues (Hg and PCB) were found in wels from the OrUk reservoir, and they exceeded the hygienic limit in some cases (PCB). Values of pollutant residues found in bullhead fished from various localities of the Labe were also increased. Above all, PCB and mercury values exceeded valid hygienic limit of the Czech Republic in some cases.Wels and brown bullhead proved to be important indicators of loading of various localities of surface waters with investigated pollutants. Wels as a predator and brown bullhead as an omnivorous and benthophagous fish are important indicators of loading of surface waters with mercury. The muscles of wels are besides those of eel (Anguilla anguilla) one of the most important indicators for the evaluation of surface waters loading with polychlorinated biphenyls.
Silurus glanis, Ictalurus nebulosus, pond, Labe river, OrUk reservoir, mercury, metals, PCBs, indicator congeners, DDT, BCB, BCB, triazinesThe objective of this study is to evaluate the suitability of representatives of Siluriformes for indication of water environment loading and to evaluate the hygienic quality of their flesh from the point of view of pollutants content. The representatives of Siluriformes (Silurus glanis, lctalurus nebulosus) sampled from fish ponds, the river Labe and the Orlik reservoir (Czech Republic) were selected for these investigations.
Materials and MethodsResidues of pollutants were monitored in Siluriformes from various localities of the Czech Republic. Sample consisting of five individuals of we Is (Silurus glanis) were taken from the ponds Bezdrev (460 ha, Fisheries Hluboka nad Vltavou), Spolsky (138 ha, Fisheries TIeboii), KaClehy (136 ha, Fisheries JindfichiIv Hradec), Vrko<: (180 ha, Fisheries Pohofelice), Novovesky (120 ha, Fisheries Pohofelice) and Bezruc (100 ha, Fisheries Ostrava) (Fig. I ).