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.

Every country must to concern the biodiversity of flora and fauna, especially in ecosystems rich with endemic and relict species. Such ecosystem is the Lake Ohrid.

In this paper, we present the results from both quantitative and qualitative composition of the Gastropod fauna from Lake Ohrid (profile HBZ-Radozda) with their vertical distribution in littoral and sublittoral region of the lake. The results of our investigations shows some changes in biodiversity and the density of gastropod communities that settle this profile, compared with the investigations made 30 years ago.

The aim of this work is to present preliminary results of the Sava River investigation at five sites within the reach from Martinska Ves (Croatia) to Šabac (Serbia). A total of 70 macroinvertebrate taxa from 13 groups were recorded, with domination of molluscs and oligochaetes. Among them 7 alien species were registered. Invasive clam Corbicula fluminea was recorded at all five sites, while invasive amphipod Dikerogammarus haemobaphes was not recorded only at locality Šabac. It is expected that the taxa list of aquatic macroinvertebrates within investigated reach will contain more species, after the identification of the rest of biological material and more detail identification of certain taxonomic groups.