Abstract: The paper describes results of studies based on four-dimensional measurements of the Sv distribution in 3m layer over the bottom in the southern Baltic area for the period 19952002. These are correlated with values of coincident environmental factors: time, depth, water temperature, salinity and oxygen levels, bottom features, estimated on the basis of survey data and wide range of methods, elaborated by the author for fish behaviour studies. The purpose of the paper is to compare results collected during acoustic surveys in the Baltic and to estimate irregularities in fish distribution potentially influencing the results of fish bottom trawling in a sense of its application for demersal fish resources assessment.