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 200_m, its mouth area is 1m2 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.