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A study of fish fauna in a small hypertrophic lake was conducted in the spring, summer, and autumn of 2006-10. In total 11 fish species representing 4 families were found. The species richness was low, depending on the season, and ranged from 2 to 7 species. A variation of species dominance, depending on the year and season, was found. Total fish abundance and biomass were varied according to the season, but differences depending on the year had been noted only in fish biomass. The fish fauna was characterized by low values in indices of diversity and the estimated turnover rate of the fauna ranged from 0.09 to 0.56, and the regression analysis showed a significant growth in its upward trend.
Background. The topmouth gudgeon, Pseudorasbora parva (Temminck et Schlegel, 1846) (known also as stone moroko), is an alien species of the fish fauna of many European freshwater ecosystems. In large quantities, its may affect negatively the fish fauna and the functioning of ecosystems. It competes for food with native fish species and they occupy their habitat. The knowledge about the invasion dynamics may help to find suitable control measures. The aim of this study was to find and observe the population of P. parva in a small river. Materials and methods. Inventory fishing on three sampling sites at the Ciemięga River was carried out from 2003 to 2007. The abundance and density of P. parva in the river were calculated. The size distribution of P. parva and its length–weight relation were determined. Abundance, density, length, and mass of the fish from all study sites were analyzed statistically. Results. P. parva was first recorded in the Ciemięga River in the autumn of 2005. The abundance of P. parva in relation to the structure of the local ichthyofauna was the smallest in the spring and the highest in autumn. The total length of P. parva ranged from 15 to 104 mm, and the mass from 0.2 to 10.4 g. Taking into account the number of the specimens, P. parva constituted between 0.9% and 57.2% of the local ichthyofauna, while its mass ranged from 0.0% to 35.1% depending on the study site and the season. The density of P. parva ranged from 72.9 to 6.5 CPUEn, while the mean value for the river was 30.6 CPUEn. Conclusion. In Polish waters P. parva is an alien species and there is still little information about its occurrence in the flowing waters. Since 2005, this species was present almost in all inventory catches in the Ciemięga River. Its presence was dependent on the kind of the habitat and the presence of predatory fish species (eg brown trout). P. parva occurring numerous may be a lot of competition for native fish species, and therefore an important problem is to understand his habitat preferences and interactions with native fish species.
This article addresses the management of Lake Skomielno as a special recreational lake fishing site, and outlines the initiatives undertaken by the reservoir’s leaseholder in order to adapt it to recreational fishing purposes. The leaseholder prepared the surrounding area and conducted intensive stocking in 2003-2005 with eight fish species (in 12 stocking forms) that are popular among recreational fishers. The stocking policy was suitable for tench and pike lakes. Prussian carp was the dominant in the catches, with pike and tench also contributing a significant share to the biomass of the fish caught. The leaseholder has performed selective fishing of brown bullhead. Control fishing with a gill net revealed the presence of 15 fish species belonging to five families. The structure of this catch was dominated by roach and perch, while the biomass structure was dominated by perch, Prussian carp, and rudd. Significant shares of the number of fish and fish biomass comprised predatory fish species at 22% and 41 %, respectively.
The ide eggs were incubated in the laboratory in three temperature ranges: 11–13, 15–16, and 18–20°C. Throughout the entire period of incubation, the live eggs were observed and samples were collected for histological assays. Microscopic slides were made to record the timing of appearance of hatching gland cells. The distribution, number, and size of the hatching gland cells, relative to incubation temperature, were determined. The cells appeared at the earliest (after 75 h of incubation) in the eggs incubated at 18–20°C and took the longest to appear (145 h) in those eggs incubated at the lowest temperature. The hatching gland cells were observed to be present only in the anterior part of the ide embryo and were lacking in the caudal part. Depending on the temperature, an embryo showed the presence of 200 to 390 hatching gland cells.
The aim of the study was to determine the contribution of pikeperch aged 0 + (Lt <10 cm) to the ichthyofauna structure as an indicator of the reproductive success of this species in Lake Miejskie where biomanipulation was performed. The treatment was carried out in late summer 2006, and comprised stocking the lake with the predatory fish species pike, pikeperch, European catfish, and eel. Gillnet monitoring catches were performed in the lake three times before biomanipulation in 2006, and then three times throughout 2007 after it. Overall, 14 fish species were noted, including four species of predatory fish. After biomanipulation, the share of predatory fish in the ichthyofauna abundance structure increased from 3.2% to 8.9%. Before biomanipulation, pikeperch accounted for more than half of the share of predators, approximately 23% of which was 0 + pikeperch juveniles (TL10 cm). Because of the fourfold increase in the number of 0 + pikeperch individuals one year after biomanipulation, the overall share of pikeperch among predators had increased to over 91%.
The knowledge on the ichthyofauna community in forest complexes in our country is mainly limited to few information on fish species found in rivers and reservoirs located in the protected areas. Hence, the aim of present study was to evaluate the importance of forested and non−forested areas, which include small rivers, on the occurrence of fish communities. The main criteria of evaluation were species richness, biodiversity and density of fish from rivers located in forested and non−forested areas in Roztocze and Puszcza Solska (south−eastern of Poland). The 12 study sites in the two groups of small rivers located on forested and non−forested areas were chosen (tab. 1). The control fishing was performed by electrofishing using IUP−12 gear. The total of 779 individuals of fish and lamprey belonging to 22 species were caught during the study. In the sections of rivers located in non−forested areas we noted 18 species, while in the rivers in forested areas – 16 ones. The analysis of the abundance domination showed that the dominant species in the rivers sections on non−forested areas were perch, roach and gudgeon, while in rivers located in forested areas: gudgeon, dace and brown trout. Simultaneously, in abundance of fish fauna from rivers in forested area a significant share of eastern sculpin, burbot and European brook lamprey were noted. The fish communities from both habitats showed similar values of biological diversity indices, but slightly higher density was observed in the rivers located in non−forested areas. The fish species composition was highly dependent on the close surroundings of the watercourse and the type of riparian zone. For the habitats from river located in non−forested areas the common, associated with aquaculture and also invasive fish species were characteristic. However, in the rivers in wooded areas, the typical for small streams and the rheophilic fish species were more frequent. The results of present study showed, that the largest differences in the dominance in fish structure and indicators of fidelity to the habitat preferences between the groups of rivers were determined.
Fish are a group of organisms that are highly sensitive to mercury (Hg) contamination of the aquatic environment. At the same time, because this element can be accumulated in tissues, it can pose a serious threat to human health. The main objective of the study was to determine the content of Hg in the muscles (HgM) and gills (HgG) of various species of fish from shallow lakes with varied physicochemical conditions. Sampling was done in 5 lakes from April to November 2012 and 2013. The concentration of Hg in fish tissues was affected by 4 variables, including ammonium nitrogen, chlorophyll-a, oxygen saturation, and temperature, and the first 2 axes explained 78.9% of total variance in Hg concentration. The concentration of Hg in muscles was widely varied depending on the fish species, and its highest concentration was observed in predatory fish such as asp and perch, while the lowest concentration of this element was found in Prussian carp, bream, and rudd. Although content of Hg increased with fish body length, in non-predatory fish this correlation was less clear. The gills of the fish contained lower concentrations of Hg than the muscles. Hg content in muscles was within acceptable weekly limits, but predatory fish consumed in large quantities by the local population may pose a potential risk for human health.
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