Abstract: This paper presents the results of continual 17-week ADCP measurements applied to investigate the migratory behaviour of the Baltic animals. The velocities of vertical migration are determined in different ways and the results are compared. Strict correlation of the moments when downward or upward migration starts with sunrise and sunset times, is confirmed. Additionally, vertical and horizontal movements of water content are examined. Even though quite slow in comparison with horizontal flow, vertical migration exists independently of other factors.