The samplings of zooplankton were taken with the Mockness net. The type of tows was oblique. The Mockness net is comprised of nine nets that have mesh size 200µm, its mouth area is 1m**2 and the net width is 1m. Both opening and closure of the net are achieved automatically through means of a computer (Wiebe et al. 1985, doi:10.1007/BF00397811). Mockness is manufactured in such a way, so that each tow can be performed at a 45o corner, which is usually achieved when the speed of the vessel equals roughly to 2kn. The filtered water volume was measured by the MOCNESS flow meter.