Iwona Psuty-Lipska¹ and Anna Garbacik-WESOŁOWSKA^2
1 Sea Fisheries Institute, Kołłątaja 1, 81-332 Gdynia, Poland
² Sea Fisheries Institute, Świnoujście Branch, Plac Słowiański 11, 72-600 Świnoujście, Poland

Key words: commercial species, non-commercial species, occurrence density indicator, frequency of occurrence, map of spatial distribution, Pomeranian Bay, Szczecin Lagoon.

Abstract.
Results of experimental catches carried out with small mesh bottom trawl nets between 1994 and 1995 were used for estimating the spatial and quantitative distribution of fish in the areas of the Pomeranian Bay and the Szczecin Lagoon. In the material collected 27 fish taxa were recorded in the Pomeranian Bay and 35 in the Szczecin Lagoon. The results of catch analyses in the Pomeranian Bay were presented in maps of the spatial distribution of species. The classification of the quantitative occurrence of fish species in the area investigated was based on a four level scale. The results were compared with statistical data of commercial catches. The contribution of non-commercial fish in experimental catches in the Pomeranian Bay varied from 40.6% in 1994 to 31.1% in 1995. In the species composition of research catches in the Szczecin Lagoon only 1% of non-commercial fish were found.