The experiment was performed on marine Teleost Serranus scriba with lower concentrations of lindane then MPC (due to our valid law). The aim of this study was to find the effects of lindane to fish activities connected with nutrition. This motive is among the strongest. It includes parameters as: number of fish movements in the presence of prey or without it and the number of onslaughts to the prey during one hour. The results have shown that the increasing of lindane concentration caused considerable decreasing and even complete cessation of activity. Interest for prey and decreasing activity of predators in the presence of prey (typical for Serranus - as a fish of prey and the hunter) endures till the moment of convulsion.

According to microbiological parameters, waters of both small rivers of eastern Backa, Serbia (Yugoslavia), are slightly and moderately polluted by organic matter at the most of the investigated localities in summer season. The satisfactory power of water selfpurification has been preserved in these aquatic ecosystems. In order to prevent further eutrophication processes, certain measures of river water protection and conservation should be undertaken, especially in stagnant parts of investigated waters. Also, the regular monitoring of water quality should be established.

Some new results of the monitoring and control of the sea-water quality along the Montenegrin coast of the Adriatic sea, Montenegro (Yugoslavia) are presented. The recent data from summer 1998 are compared with some previous results. So, increasing of temperature mean values and decreasing of salinity and sea-water density were found in comparison with the previous years in the whole investigated area. At the same time, the quality of the sea is growing worse, step by step. Faster changes were found in Boka Kotorska Bay, Montenegro (Yugoslavia) than outside of the bay, in the zone which is exposed to the stronger influence of the open sea. Finally, the most essential conclusion is that the solution of wastewater discharges becomes more and more important, especially in semienclosed Boka Kotorska Bay (Adriatic Sea, Montenegro, Yugoslavia).

There was investigated potential erodibility of two small experimental watersheds, which belongs to the watershed of Topciderska river, Serbia (Yugoslavia), on the base of geological structure of the watershed area. The investigations of potential erodibility of watersheds were included the analysis of tectonical and every geological formation, as from viewpoint of its possible erodibility as well as of possible sediment type (load, suspended and mixed) which were originated in desintegration processes. The sediment type domination, which was produced from watershed, was confirmed from granulometric composition of sediment in experimental watersteams. The synthesis of results of this analyses is presented with map of potenatial source of sediments from experimental watersheds.

Expert system (ES) is a software which unites mathematical models, empirical knowledge, expert evaluation, engineering intuition, heuristic rules and necessary informations which through the inference engine gives useful advise to the decision maker, to reach a correct and timely decision. The objectives of ES cover a wide range of tasks of protection of waters, out of which the following seem to be the most important: diagnostics, monitoring, estimation, interpretation, planning and design of systems, maintenance, trouble shooting, education, management.

Studies of phytoplankton in the Montenegrin coastal sea (Adriatic Sea), Montenegro (Yugoslavia), have been done in August and September 1998. Simultaneously, investigations were carried out in the area of Boka Kotorska Bay (Kotor and Tivat Bays) and outside the Bay, i.e. in the zone exposed to the influence of the open sea (Petrovac and Budva). It was found that the density of microphytoplankton is higher during summer, than in the autumn. So in the summer-period, as a consequence of stronger eutrophication process, mean-value of microphytoplankton density was 10**5 cells/cubic dm, and in autumn 4 x 10**4 cells/cubic dm. On the contrary, mean-value of nanophytoplankton density was higher in the autumn (5.2 x 10**6 cells/cubic dm) than in summer (3.5 x 10**5 cells/cubic dm), being a consequence of a decreasing eutrophication during colder period of the year. Having in mind the direct influence of the open sea outside the Bay, it is intelligible that population density of both phytoplankton size-fractions is lower along the Montenegrin coast, than in the Boka Kotorska Bay (Montenegro, Yugoslavia).

The paper presents results of the hydroecological investigations of the Vlasina river basin, Serbia (Yugoslavia). The researches were performed in May and September 1996, as a part an annual investigation cycle. Samples were collected from five localities on the Vlasina river, and on two spots on its main tributaries - the Gradska river and Luznica, just before entering into the Vlasina. Qualitative and quantitative data on composition of phyto- and zooplankton, periphytic and benthic communities together with data obtained from physico-chemical water examinations were analysed to assess water quality of examined water courses. The results of performed monitoring were compared with informations on the sources of pollution, as well as with the data on hydrology, geomorphology, demographic variations, and recent development of tourism and industry in the Region in order to assess environmental quality of aquatic ecosystem and to suggest the conservation strategy.

From two locations in the Vizelj channel (Serbia, Yugoslavia) in the early spring and before irrigation water samples were systematically taken in order to examination the content of harmful and dangerous matter. Content of Cd, Pb, Hg, As, Cr, Ni, F, Cu, B in water samples was analyzed. The origin of these elements in the water and the effect of potentinal pollutants were analyzed. Also, deviation of content of these elements from permissible amounts which were announced in the Book of Regulation was commented.

It has been done the analysis of the physical and chemical characteristics of the water from two households in the village Berkovac in the foot of the mountain Maljen, Serbia (Yugoslavia). These households are supplying from two different springs. The water from the spring "Dobracinovica izvor" is contaminated and it is not for use, but the quality of the water from the hill Kulica is satisfactory. Both of them belong to the group of cold mineral waters.

Determination of total organic carbon content (TOC) and trihalomethane formation potential (THMFP) as well as correlation of those two parameters is recommended for monitoring of water bodies which are considered as drinking water resources. Those parameters would enable a categorization of water bodies from the protection point of view as well as from view of their usage as drinking water sources. Relationship between TOC and THMFP is dependent on the origin and the structure of organic matter in water. In this paper the correlation of TOC and THMFP is given for different kind of resources.