Qualitative and quantitative analysis of organochlorine insecticide residues were conducted in water, sediment, aquatic plants and animals from 3 freshwater reservoirs. Ninety water samples, 90 sediment samples, 397 aquatic plants samples and 121 aquatic animals samples were collected during March-April and August-September 1989. There were about 14 kinds of aquatic plants, such as water hyacinth, water lettuce, algae and water lilly etc. Aquatic animals are fish, shrimps and snails, but most of them are fish. They are striped snake-head fish, carp and catfish etc. Total samples of 698 were analyzed by using gas chromatographic techniques at Agricultural Toxic Substances Division. The results indicated that 5 kinds of insecticides were found in most samples. They were lindane, heptachlor, aldrin, dieldrin, DDT and derivatives. Dieldrin was detected at higher concentration and found in all samples. The residue level of dieldrin ranged from 0.01-0.12 ppb in water, 0.005-0.036 ppm in sediment, 0.001-0.138 ppm in aquatic plants and 0.001-0.037 ppm in aquatic animals respectively. The accumulation of dieldrin residue in water and aquatic plant samples from all reservoirs are not different but the level of dieldrin residue in sediment samples from Bueng Boraphed is higher than the other 2 reservoris. However the levels of dieldrin residue in sediment, aquatic plant and aquatic animal samples higher than those in water samples respectively.

Food composition of Abramis brama was studied in the shallow, meso-eutrophic Hamry reservoir (Czech Republic). Fish were sampled during the daytime in the pre-spawning period (April), the post-spawning (June), summer (July) and autumn (October) in 2011. The bream sampled comprised two main size groups: small (124-186 mm) and large (210-315 mm) standard length. Twenty specimens of each size group (except April - 40 large fish) were taken for analysis on each sampling occasion. Food composition was evaluated using gravimetric methods. Over the whole season, detritus and aquatic vegetation were the dominant dietary items taken. During summer, the diet of large bream comprised mainly aquatic vegetation. Benthic macroinvertebrates and zooplankton formed a minor part of bream diet over the whole season. Specific food habits of bream could be explained by specific conditions within the reservoir and available food resources.

The monkey goby originating from the Ponto-Caspian area, has appeared in increasingly wide-spread areas of Hungary. In the Tisza-to water reservoir in North-Eastern Hungary along the Tisza River, 83 first summer samples of the fish were collected in the vicinity of Tiszafured on October 21st, 2000. The average length of the fish, not including the caudal fins, was 50,4 mm, the average weight was 2.1 g. Their alimentari canals contained mostly gnats (Chironomidae), but also the relative amount of the taxons Copepoda, Ephemeroptera, Ostracoda and Odonata was notable.

Species composition of algae and aquatic plants in Bung Si Phi swamp were investigated during February to July 1985. The samples were collected randomly 3 times in February, April and July respectively. Thirty-five species of algae and seven species of aquatic plants were observed. Closterium sp., Cosmarium sp., Mougeotia sp., Onychonema sp., Pediastrum sp., Tetraedron sp., Anabaena sp., Oscillatoria sp., and diatom were dominant species of algae population while Ceratophyllum demersum, Hydrilla verticillata and Najas minor were dominant species of aquatic plant and occupied major area of the swamp. The proximate analysis of Spirogyra sp. showed 12.81 percent of protein nitrogen content by dry weight. The protein contents of aquatic plants ranged from 10.79 to 13.99 percent by dry weight.