During the 1981-1996 period, qualitative and quantitative structure of oligachaeta communities as indicator of the eutrophication process was investigated in the lake Palic (the 2nd oxidation lake), Serbia (Yugoslavia). The mean annual number of oligochaetes was related to nutrient concentration (total nitrogen and total phosphorus). The analysed data for both oligochaete community and nutrients, leads to the conclusion that the second oxidation lake Palic can be classified as an highly eutrophic environment, with tendency towards dystrophic, particularly in past two years.

In this paper are presented autochthonous and all other alochthonous famous fishes in Lake Ohrid and its catchement area (The Former Yugoslav Republic of Macedonia). Introduction of new species in lakes and rivers in the Former Yugoslav Republic of Macedonia is prohibited, especially in Lake Ohrid and catchement area. The most probable period and possible way of introduction are presented and the reason of that introduction, as well. It is necessary, in the future, more attention to be paid on Lake Ohrid protection from introduction of new species, which may cause big changes in Lake Ohrid dynamics.

The analysis of the phytoplakton and phytoperiphyton communities in the Palic lake (Serbia, Yugoslavia), has been performed with aim the water quality evalution. The determining and following proportional presence of phytoplankton were in the fourth sector of lake during 1998, 1999, and 2000. During the period of investigation, the phytoplankton community was characterized by forms of Chlorophyta, Cyanophyta, Euglenophyta and Bacillariophyta. During the investigation it was perceived the change in proportional participation in the presence of the four alga group mentioned above. The most representative percent was the Chlorophyta group, with values from 44.4%, to 54.7%. The other phytoplakton group has less values of percentage in the values.

The lake Provala near Vajska (Serbia, Yugoslavia) was created by the embankment performation during high Danube river levels in 1924. It is a very important water ecosystem of natural origin, which is a fact of great importance for exact biological and ecological research. Miljanovic (1996) and Pujin (1997) present the first lake Provala water state data. They emphasise the reinforced eutrophication process in the shore region. This paper presents the review of the macrophytes vegetation of the lake Provala recent state for the first time, with special attention to dominant plant species. Based on the present taxons analysis, as well as water chemical parameters analysed (NH4(+), NO3(-), NO2(-), PO4(3-), HPK, BPK, pH), it can be concluded that the eutrophication process is present in this water micro-reservoir. It is especially true for the shore region and shallow waters, where the process is already well under way and very fast. These research results can be used to efficiently protect this natural water ecosystem.

Oxygen aspect of water pollution of Skadar lake, Montenegro (Yugoslavia) is considered in this paper. Water analysis data in the period of 1991-1998 were used to establish relevant parameters, oxygen saturation (%O2), and five day biochemical demind (BPK5). Those data were supplied by Hydrometeorological Institute in Podgorica, Montenegro (Yugoslavia). Measurements were taken from three places in northern part of Skadar lake, where the increased water pollution is expected, and from southeastern part of the lake, out of source of pollution directly influence. According to results from this research, there is close relation between water pollution and oxygen water balance. Parts of the Skadar lake with low water circulation are especialy susceptible (place Kamenik). In the 1991-1995 period, this phenomena is manifested with variation depending of the chosen area and year. After some improvement of water quality in the 1996-1997 period, there is noticeable increase of water pollution in 1998 at all places. Supersaturation was identified by the percentage of O2 in Skadar lake area at whole.

Water quality analyses were performed on littoral water samples, collected on Lake Ohrid in 2002 (January, February, June, July, August and September). Several microbiological parameters were compared. The number of Escherichia coli, the number of organotrophic bacteria and the phosphatase activity index were measured. Samples were collected along the shore of Lake Ohrid, i.e. at the village of Pestani, at Hotel Metropol, in Ohrid Bay and at the lake inflow of River Velgoska. The results of the study show that the different parameters are not compatible in terms of water quality characterization. The differences found are discussed below.

This report presents investigation performed as a part of a wider study desined to examine the level of pollution effects on fish in Ohrid lake (The Former Yugoslav Republic of Macedonia). Faunal investigation of the fish Barbus meridionalis petenyi Heck. were carried out at the five localities in Ohrid lake. Microscope analysis of histological preparation of barbel hepatic tissue displayed a dominant presence of granulomatous inflammation on a level of hepatocelular parenchyme and cholangiofibrosis on a level of hepatic bile duck. The analysis did not exhibit any correlation between the granulomatous inflammation and the manifestation of the cholangiofibrous alterations.

Sasko Lake, with surface area of 3.4 square km and depth of about 8 m, is situated is southwestern part of Montenegro (Serbia&Montenegro), within the hydrosystem of Skadarsko Lake. During 2002 and 2003, seasonal dynamics of main hydrographic, physical, chemical and biological parameters of this ecosystem was monitored. Reference measuring spots are defined, and in these places all future monitoring of system state will be accomplished. Also done are the preliminary batimetric measurements and maps of spaces suitable for development of breeding activities. In order to develop aquaculture as a strategic interest of Montenegro (Serbia&Montenegro), it is necessary to utilize these important potentials and place this important natural resource in full fuction. Included are the list of all fish species living in the lake, as well as the suggestion of species that could be suitable for commercial breeding.

In this paper are presented the length and weight growth of bleak Alburnus alburnus alborella Filippi from Lake Ohrid, R. Macedonia. The results of the length growth are presented by percent growth, absolute length growth in mm., the length growth rate (CI), the length growth constante (CIt), and growth characteristic (K). The weight growth are presented by percent growth and absolute weight growth in grams.