Amplified and accelerated eutrophication process is a characteritic of a whole variety of small and medium-sized water-bodies, such as channel systems, microreservoirs, ponds, lakes and bank regions of many even bigger ecosystems. During the process, in relatively short period of time, the upper capacity limit of a certain biotop is far too exceeded, which leads to reduced ability of ecosystem's autopurification. As a consequence of such degradation, ecosystem faces a serious discrepancy between members of a biocenosis e.g. in ration producers/consumers/decomposers, which, in the end, causes destruction, e.g. dystrophy of the hydroecosystem. The introduction of diverse fish communities, can, therefore, be one of the basic measures for enabling a sustainable trophic stability, in a sense of keeping a dynamic balance. This measure includes carefully planed fish community - it should consist of three basic components of a trophic food web (planktivore and macrophytovore, bentivore and carnivore). Apart from enabling certain biodiversity considering particular fish species (both quantitative and qualitative), care must be inevitably taken of age structure, as well as fish stock and fishing dynamic, concerning the number, quantity and age.

A complex ichthyological analysis of the individual sections of the DTD (Danube-Tisza-Danube)-Backa canal system (Serbia, Yugoslavia) performed during 1996 vegetation period 23 fish species from 7 families. On the basis of the occurrence and abundance of indicators and limnosaprobic parameter, water quality of the analyzed canal sections was found to be beta-mesosaprobic index ranging from 2.15 to 2.21. The obtained results show that water quality of this DTD (Danube-Tisza-Danube) canal sections (Bajski Kanal, Odzaci-Sombor, Vrbas-Bezdan and Novi Sad-Savino Selo canals) corresponds to its purpose. The fish community representing an important factor of a whole aquatic biocenose, in addition to its undoubtedly indicator values also representing an active factor in the process of selfpurification and quality preservation of whole hydrosystem.

Legacy halogenated compounds, including polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and emerging organo-halogen pollutants such as Dechlorane Plus (DP), were detected in fish from an old industrial region in Northeast China. PCBs and PBDEs were detected in all of the samples, with concentrations ranging from 38.15 to 170.51 ng/g lipid weight, and 9.40–39.69 ng/g lipid weight, respectively. DP was detected in more than 90% of the samples with concentrations ranging from not detected (ND) to 470 pg g/g lipid weight. Compared with similar data in other areas of the world, PCBs, PBDEs and DP in fish from Liaohe River were at medium or low level. An unusually high percentage of PCB-209 was first reported in the fish samples collected from China. Other halogenated pollutions, such as dichlorodiphenyltrichloroethane (DDT) and its metabolites, octachlorostyrene, chlorinated anisole, chlorinated thioanisole, triclosan-methyl, and other pesticides, have also been identified in the fish samples.

We investigated the impacts of effluent discharge from small flow-through fish farms on stream water characteristics, the benthic invertebrate community, whole-system nitrate uptake, and ecosystem metabolism of three tropical headwater streams in southeastern Brazil. Effluents were moderately, i.e. up to 20-fold enriched in particulate organic matter (POM) and inorganic nutrients in comparison to stream water at reference sites. Due to high dilution with stream water, effluent discharge resulted in up to 2.0-fold increases in stream water POM and up to 1.8-fold increases in inorganic nutrients only. Moderate impacts on the benthic invertebrate community were detected at one stream only. There was no consistent pattern of effluent impact on whole-stream nitrate uptake. Ecosystem metabolism, however, was clearly affected by effluent discharge. Stream reaches impacted by effluents exhibited significantly increased community respiration and primary productivity, stressing the importance of ecologically sound best management practices for small fish farms in the tropics.

This study investigated the relationship between contaminant body burden and the oxidative stress status of the gills and livers of two wild fish species in the Furnas Hydroelectric Power Station (HPS) reservoir (Minas Gerais, Brazil). Gills and livers presented similar pathways of metals and organochlorine bioaccumulation. During June, organochlorines were associated with lipid peroxidation (LPO), indicating oxidative stress due to the inhibition of the antioxidant enzymes superoxide dismutase and glutathione peroxidase. In the most polluted areas, metal concentrations in the liver were associated with metallothionein. During December, contaminants in the gills and liver were associated with catalase activity and LPO. Aldrin/dieldrin was the contaminant most associated with oxidative damage in the livers of both species. This integrated approach shed light on the relationship between adverse biological effects and bioaccumulation of contaminants inputted by intensive agricultural practices and proved to be a suitable tool for assessing the environmental quality of man-made reservoirs.

Polyhalogenated 1,1′-dimethyl-2,2′-bipyrroles (PDBPs) are halogenated natural products (HNPs) previously shown to bioaccumulate in marine mammals and birds. Since their discovery in 1999, six hexahalogenated and a few lesser halogenated congeners have been identified in diverse marine mammal samples. Here we report the identification of 17 additional hexahalogenated PDBPs in the blubber extract of a humpback dolphin (Sousa chinensis) from Queensland, Australia. Thirteen of these new PDBPs were also detected in an Australian sea cucumber (Holothuria sp.). Additional samples were also tested positive on several new PDBPs, including an Australian venus tuskfish (Choerodon venustus) as well as a white whale (Delphinapterus leucas) and a sperm whale (Physeter macrocephalus) from the Northern Hemisphere. GC/ECNI-MS-SIM quantification of the molecular ions was carried out with the help of synthesized standards. The sum concentration of PDBPs was 1.1 mg/kg lipid in the humpback dolphin and 0.48 mg/kg lipid in the sea cucumber.

The interaction of xenobiotics is common in aquatic ecosystems; therefore, we wanted to evaluate if trenbolone (TB) modulates the effects of 17α-ethinylestradiol (EE2). Male eelpout (Zoarces viviparus) were exposed to 5 ng L−1 EE2 continuously for 19 d (EE2-C) or discontinuously (11 d, EE2-D) alone or in combination with low (50 ng L−1, TBL) or high (500 ng L−1, TBH) concentrations of TB (19 d). Exposure to EE2 caused reduced gonadosomatic index, increased plasma vitellogenin concentrations, up-regulated vtg and era mRNA expression and severe alterations in gonadal histology. TBL and TBH did not affect plasma vitellogenin, era or vtg mRNA expression. TBL and TBH did not counteract the EE2-induced increase in plasma vitellogenin and reduction in 11-ketotestosterone whereas TBH counteracted the EE2 induced increase in vtg and era mRNA expression. Exposure to TBH and EE2-C + TBH lead to severe gonadal histology alterations. TBL and EE2-D + TBH exposed fish showed less histopathological alterations.