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Electrofishing was carried out at 66 sites in the Słupia River system. Twenty-five fish species were noted. The most frequent were trout (Salmo trutta), three-spined stickleback (Gasterosteus aculeatus) and bullhead (Cottus gobio). Three groups of sampling sites were distinguished based on fish densities and species composition. These fish assemblages inhabited places that did not differ widely with regard to the 13 environmental parameters assessed. Although there were also no clear sequences of assemblages, the distinct influence of lakes and impoundments was evident.
The aim of this study was to describe the ichthyofauna composition of the Goczałkowice Dam Reservoir based on records in fisheries logs of commercial catches conducted in this basin over a 16-year period (1986-2001). The results indicate that the Goczałkowice Reservoir was managed appropriately during this period. The dominant species in the reservoir was bream at 49.74% of the overall biomass of all the fish caught. The second most common fish was a mix of small fish (31.62%). Evidence of the rational management of this basin is that 17% of the ichthyofauna are predacious fish, with pikeperch comprising 56% of all the predacious fish caught.
The species composition and biomass of the fish passing through the chamber fishway located in the Rożnów Reservoir dam in the fall, spring, and summer was determined. Fish samples were collected by electrofishing in the resting chamber. The numbers of other species were estimated in the remaining chambers. In the 1997-2003 period the presence of seventeen species was recorded. The decided dominant was bleak, which comprised 79.2% of all fish at 28362 specimens. Cyprinids comprised 98.8% of all the fish examined. Significant variations were observed in the abundance of fish in particular years and seasons. Fish from older year classes passed through the fishway. Only common bream, barbel, and possibly bleak were undertaking spawning migrations. Only three sea trout specimens were observed in the study period. In order to gain a complete picture of the fish passing through the fishway, monitoring should be conducted on a permanent basis.
Mycoflora developing on some fish species, recently introduced to Polish waters, has not been known. The authors incubated muscles of four fish species (monkey goby, Neogobius fluviatilis; racer goby, N. gymnotrachelus; Chinese sleeper, Perccottus glenii; and stone moroko, Pseudorasbora parva caught in the drainage area of the Bug River) in water taken from 6 different places. A total of 59 fungus species were found to grow on fish muscles studied: Achlya ambisexualis, A. americana, A. caroliniana, A. crenulata, A. debaryana, A. diffusa, A. dubia, A. intricata, A. klebsiana, A. oblongata, A. oligacantha, A. orion, A. polyandra, A. prolifera, A. proliferoides, A. radioasa, A. rodrigueziana, A. treleaseana, Aphanomyces irregularis, A. stellatus, Blastocladiella britannica, Blastocladiopsis parva, Catenaria verrucasa, Cladolegnia unispora, Dictyuchus monosporus, Isoachlya monilifera, Leptolegnia caudata, Leptomitus lacteus, Phlyctochytrium aureliae, Pythium afertile, P. aquatile, P. arrhenomanes, P. butleri, P. dissotocum, P. hemmianum, P. intermedium, P. myriotylum, P. ostracodes, P. periplocum, P. tenue, Rheosporangium aphamidermatus, Rhizophlyctis hirsutus, Rhizophydium laterale, R. macrosporum, Saprolegnia asterophora, S. diclina, S. eccentrica, S. ferax, S. hypogyna, S. litoralis, S. mixta, S. monoica, S. parasitica, S. pseudocrustosa, S. shikotsuensis, S. torulosa, S. uliginosa, Thraustotheca clavata, Zoophagus insidians. The results obtained may be important to ichthyopathologists, because 25 of the above-mentioned fungi are known as necrotroph or parasites of fishes.
In sixteen early medieval settlement layers of the Wolin-Town, which correspond chronologically to the period from 7th to mid 13th century, the occurrence of 16 463 bone remains of fishes was stated, of which 9 799 pieces were identified anatomically and their specific affiliation was determined. These bones as well as scales found in the excavation belonged to 27 fish species. Amongst them were 13 cyprinid and 3 salmonid species. Based on the comparative study of the bones, a total of 4 645 fish were determined and their estimated weight amounted to 9 308 kg. The quantitative dominants were: Stizostedion lucioperca L. (31.6%), Abramis brama L. (26.2%), Perca fluviatilis (15.5%) and Rutilus rutilus L. (11.3%). The total weight dominants were: Stizostedion lucioperca L. (36.4%), Acipenser sturio L. (35.4%), and Abramis brama L. (14.8%).
Fifteen sites were selected in the upper Wisłoka River drainage basin. Twelve species were recorded. In terms of abundance the dominant species in the material collected were Phoxinus phoxinus (L.), Leuciscus cephalus (L.) and Barbus peloponnesius Val. P. phoxinus clearly dominated in the smallest streams and there were significant local contributions of Salmo trutta m. fario L. to the fish biomass. In the larger streams, the minnow contribution decreased while chub and spotted barbel dominated in the biomass. Spirlin Alburnoides bipunctatus (Bloch) was also relatively abundant. Among the trout caught, relatively small specimens dominated. Poaching was most probably responsible for the lack of larger specimens in the samples. The small impoundment on the Wisłoka River and changes in stream beds caused by gravel exploitation, regulation and forestry management works also had an adverse impact on the ichthyofauna of the studied basin.
This article gives an overview the impact hydroelectric power facilities on ichthyofauna and river ecosystems. Issues addressed include the destruction of fish by grates and turbines; disturbances in the hydrological regime of rivers; changes in the water physicochemical regime resulting from damming; the muddying of spawning and feeding grounds. Suggestions are made for counteracting these disadvantageous transformations. This is achieved by equipping hydroelectric facilities with appropriate safety devices that lead fish away from the facility to a secure place where they can swim safely downstream, and also eliminate sharp fluctuations in water level that can occur below dams. It was determined that none of the existing methods eliminate ichthyofauna losses. It is recommended to combine several protection methods such as grates and electric barriers. Due to the negative impact hydroelectric plants have on the ichthyofauna, it is essential that the energy consumers participate in the costs of fish stocking to compensate for losses.
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