Prisustvo i populacione karakteristike invazivne vrste amurski spavač (perccottus glenii) u mrtvajama u jugoistočnom delu Poljske

Amur sleeper (Perccottus glenii, Dybowski 1877) is fish which in recent years has been regarded as an alien fish species in natural water ecosystems of Central Europe. In Poland, it was first recorded in 1993 in the middle part of the Vistula River. Because of its morphological and biological predispositions it is a threat to natural water ecosystems. This fish is characterized by high voracity, resistance to adverse environmental factors and a number of features conducive to invasion. The aim of this study was to determine the presence, abundance and percentage contribution of Amur sleeper in the fish fauna of oxbow lakes located in south-eastern Poland. The study was conducted on two different terms (June and August) in 2012 in six oxbow lakes (No 1-6) located in the Wieprz River basin. Control fishing was carried out using electric fishing gear (IUP-12, 220-250V, 7A). All caught fish were identified to species and their total length (Lt; ± 1 mm) and weight were measured (W; ± 0.1 g). The species composition of the fish fauna of the oxbow lakes and the abundance of Amur sleeper were determined, as well as the size structure and density (in CPUE, i.e. ind.*100m-2*h-1 of fishing) of Amur sleeper. A total of 14 fish species were found in the oxbow lakes. Amur sleeper was reported in four of the six surveyed oxbows. The total length of Amur sleeper ranged from 34 mm to 128 mm (on average 55 ± 26 mm) and varied depending on the study site. The average biomass of Amur sleeper was 5.4 g (± 7.3 g), ranging from 1.3 g to 11.8 g. The proportional contribution of Amur sleeper in the abundance of fish ranged from 40% in the oxbow in the vicinity of Latyczów (No 2) to 67.3% in the oxbow lake near the town of Wał (No 6). The density of this alien species ranged from 4.0 to 35.6 CPUE and depended on the study site. The size structure of the Amur sleeper population was clearly dominated by individuals with a total length of less than 50 mm. To identify and determine the routes of dispersion of Amur sleeper into new areas, continuous fish fauna monitoring should be conducted. Moreover, it would be useful to find biological features of this species that would enable its elimination from freshwater ecosystems.Amurski spavač (Perccottus glenii, Dybowski 1877) je vrsta ribe koja se u toku poslednjih godina smatra alohtonom vrstom za prirodne vodene ekosistemime Centralne Evrope. U Poljskoj je prvi put zabeležena 1993. godine u srednjem delu reke Vistula. Zbog njenih morfoloških i bioloških predispozicija ona predstavlja pretnju za prirodne vodene ekosisteme. Ova vrsta ribe se karakteriše velikom proždrljivošću, otpornošću na nepovoljne faktore sredine i brojnim drugim odlikama karakterističnim za invazione vrste. Cilj ove studije je bio da se odredi prisustvo, abundanca i procentualni udeo amurskog spavača u fauni riba u mrtvajama koje se nalaze u jugoistočnom delu Poljske. Istraživanja su obavljena u toku dva dana 2012. godine i obuhvatila su šest mrtvaja (No 1-6) koje se nalaze u basenu reke Wieprz. Izlov ribe je izvršen korišćenjem aparata za elektroribolov (IUP-12, 220-250V, 7A). Svi izlovljeni primerci riba su određeni do nivoa vrste i izmerena je njihova totalna dužina (Lt; ± 1 mm) i totalna težina (W; ± 1 g). Određen je ihtiofaunistički sastav mrtvaja i abundanca amurskog spavača, kao i dužinska i težinska struktura i gustina (kao CPUE, tj. ind.*100m-2*h-1 izlovaljavanja) ove vrste. Ukupno je nađeno 14 vrsta riba u istraživanim mrtvajama. Amurski spavač je nađen u 4 od 6 ispitivanih mrtvaja. Totalna dužina amurskog spavača je bila u rangu od 34 mm do 128 mm. (u proseku 55 ± 26 mm) i varirala je u zavisnosti od istraživanog lokaliteta. Prosečna biomasa amurskog spavača je bila 5.4 ± 7.3 g i varirala je od 1 g to 12 g. Proporcionalni udeo amurskog spavača u abundanci riba je varirao od 40% u mrtvaji u blizini lokacije Latyczów (No 2) do 67.3% u mrtvaji u blizini grada Wał (No 6). Gustina ove alohtone vrste je varirala od 4.0 do 35.6 CPUE i zavisila je od istraživanog lokaliteta. U dužinskoj strukturi populacije amurskog spavača dominirale su jedinke sa totalnom dužinom manjom od 50 mm. U cilju identifikacije i određivanja puteva širenja amurskog spavača u nove oblasti, potrebno je vršiti kontinualni monitoring ihtiofaune. Štaviše, bilo bi korisno pronaći biološke karakteristike ove vrste koje bi omogućile njenu eliminaciju iz slatkovodnih ekosistema

Changes in a Fish Community in a Small River Related to the Appearance of the Invasive Topmouth Gudgeon Pseudorasbora parva (Temminck & Schlegel, 1846)

In recent years, the topmouth gudgeon (Pseudorasbora parva) has been one of the most invasive fishes in Europe. Pseudorasbora parva can potentially affect ecosystems, fish communities, and particular fish species. Electrofishing was carried out over a five-year period at three study sites in the Ciemięga River (eastern Poland) before and after P. parva had been found in the river. Changes in the occurrence, abundance, and density of native fish species after the appearance of the invader were determined. Changes in the species’ richness were calculated, and correlations were estimated between the occurrence and density of P. parva and particular fish species and richness indices. The presence of P. parva has not affected the density of native species but coincides with a significant increase in estimated species richness and the total density of fish. There was a significant relationship between the presence of this invasive species and the fish community’s composition, though the PERMANOVA result was unclear with regards to site-specific effects. Moreover, tench and bleak were associated positively, whereas Eurasian perch and sunbleak were associated negatively with the occurrence of P. parva. Pseudorasbora parva density was highly correlated with Cyprinidae density (excluding P. parva), species richness, and the Margalef diversity index. Thise study has shown that the presence of predatory fish in the river (Salmo trutta L.) may reduce the numbers of invasive P. parva

Indirect effect of environmental factors on interactions between microbial and classical food webs in freshwater ecosystems

The role of environmental factors in aquatic ecosystems results from basic lake characteristics, human disturbances (‘cultural eutrophication’) and climate-related trends in the physical and chemical components of lakes. Although the influence of environmental factors on the abundance of aquatic animals is fairly well documented, less has been done to research their influence on food web interactions. The aim of the study was to evaluate microbial and classical food webs in lakes, with special emphasis placed on the role of environmental factors as influencing strengths. Variation partitioning, based on redundancy analysis, revealed that environmental factors played the most important role in structuring aquatic communities by accounting for 87.5% of their variation. Among all the factors measured, total solids (TS), transparency (Secchi disc) and temperature were most closely related to the variation in trophic communities. The analyses of food web interactions under low and high levels of those factors revealed that they differently influenced strengths among food web components. The strongest relations among distinct trophic levels were found under conditions of low TS, the lowest number of relations was found under conditions of low temperature. Only in low TS did bacteria correlate significantly with biogenes. Under high TS, bacteria positively influenced plenty of higher trophic levels. Top-down control was observed under conditions of high temperature. Conditions of low and high transparency did not diversify food web interactions. The obtained results can broaden our knowledge of the response of food webs to environmental factors in advanced stages of global eutrophication of water bodies and in the early stage of projected trends of global climate change.While the influence of environmental factors on the abundance of aquatic animals is fairly well documented, less has been done to research their influence on food web interactions. Among a plenty of environmental factors measured, total solids, transparency and temperature were most closely related to the variation in trophic communities. The analyses of food web interactions under low and high levels of those factors revealed that they differently influenced strengths among food web components

The role of abiotic and biotic environmental factors in shaping epiphyton on common reed in shallow, hydrologically transformed, temperate lakes

Epiphytic algae are an important group of organisms involved in primary productivity, nutrient cycling, and energy transfer in littoral food webs. However, multifactorial studies conducted on epiphyton on the same substrate across a spectrum of environmental parameters are very limited. Here, we present first complex field study on the role of abiotic and biotic factors in shaping the species richness, diversity, abundance, and biomass composition of epiphyton on common reed in four shallow lakes with different trophic status, water and fish management, and the abundance and structure of potential algal grazers: littoral crustaceans and fish. The obtained results revealed that the algal taxa richness was the lowest in the hypertrophic lake and the highest in the meso-eutrophic lake. Epiphyton abundance (predominated by pennate diatoms) and biomass were found to be the highest in eutrophic water bodies. Biomass consisted primarily of diatoms, but we found the seasonal predominance of filamentous Chlorophyta (in the eutrophic lakes) and Chlorophyceae (in the meso-eutrophic lake). Redundancy analysis (RDA) showed that the frequency of water level fluctuations was the most significant variable in the composition of epiphyton. RDA also revealed the importance of grazing pressure of fish. Thus, in hydrologically transformed lakes, man-made factors may be of great relevance in the development of epiphytic algae

A Food-Safety Risk Assessment of Mercury, Lead and Cadmium in Fish Recreationally Caught from Three Lakes in Poland

Heavy metals are introduced into water due to anthropogenic activities and can significantly affect an entire ecosystem. Due to their close integration with the water environment, fish are a sensitive indicator of contamination. In addition, fish is an important element in human diets, therefore, monitoring the concentrations of metallic contaminants in their meat is particularly important for food safety. This study aimed to assess the pollution of water ecosystems with selected toxic heavy metals in lakes Dratów, Czarne Sosnowickie, and Syczyńskie. The concentration of Pb, Cd, and Hg in water, sediment, and freshwater fish muscle tissue was determined, and a food safety assessment was performed. The analysis of water and sediments showed that the sediments were characterised by a significantly higher concentration of heavy metals. Presumably, this ecosystem element plays an important role in the uptake of heavy metal contaminants by fish whose levels were higher in planktonophagous and benthophagous fish species as compared to predatory fish. The food safety assessment showed that amounts of heavy metals in the muscle tissue posed no threat to the health of consumers ingesting that fish species, neither individually (THQ) nor collectively (TTHQ)

The role of abiotic and biotic environmental factors in shaping epiphyton on common reed in shallow, hydrologically transformed, temperate lakes

Epiphytic algae are an important group of organisms involved in primary productivity, nutrient cycling, and energy transfer in littoral food webs. However, multifactorial studies conducted on epiphyton on the same substrate across a spectrum of environmental parameters are very limited. Here, we present first complex field study on the role of abiotic and biotic factors in shaping the species richness, diversity, abundance, and biomass composition of epiphyton on common reed in four shallow lakes with different trophic status, water and fish management, and the abundance and structure of potential algal grazers: littoral crustaceans and fish. The obtained results revealed that the algal taxa richness was the lowest in the hypertrophic lake and the highest in the meso-eutrophic lake. Epiphyton abundance (predominated by pennate diatoms) and biomass were found to be the highest in eutrophic water bodies. Biomass consisted primarily of diatoms, but we found the seasonal predominance of filamentous Chlorophyta (in the eutrophic lakes) and Chlorophyceae (in the meso-eutrophic lake). Redundancy analysis (RDA) showed that the frequency of water level fluctuations was the most significant variable in the composition of epiphyton. RDA also revealed the importance of grazing pressure of fish. Thus, in hydrologically transformed lakes, man-made factors may be of great relevance in the development of epiphytic algae