Zooplankton was collected by Multinet vertical hauls (Hydrobios
GmbH, Kiel, Germany). The equipment consisted of a net frame with
an opening of 0.25m2, fitted alternativelywith 100 and 500 μmmeshed
nets (L=2.5 m, diameter at the end=0.11 m) and stabilized by V-fin
depressor. Each net ended in a cod-end consisting of a plastic bucket
with side windows covered by gauze. The two flowmeters, mounted inside
and outside of the frame,measured the amount of water filtered by