WINTER CONDITION OF MARINE PLANKTON POPULATIONS IN SAANICH INLET, BC, CANADA .3. MESO-ZOOPLANKTON

Seasonal changes in the species abundance of surface meso-zooplankton was monitored during spring, winter, and fall in Saanich Inlet, British Columbia. Small copepods were the dominant organisms during winter (Pseudocalanus minutus (Kröyer), Paracalanus parvus (Claus), Oithona helgolandica Claus, and Corycaeus anglicus Lubbock) while Calanus spp. were relatively rare. Pseudocalanus minutus was able to graze the flagellates which dominate winter phytoplankton populations but Calanus glacialis Jaschnov was not. There appeared to be active movement of small copepods towards the shallower depths where phytoplankton concentrations were highest. Pseudocalanus minutus was able to obtain its minimum energy requirement during winter by filter-feeding. Reproduction continued throughout the winter but at reduced rates. Growth was slowed at stages C-IV and C-V during winter with moulting to adult beginning immediately after a late winter increase in primary production. © 1979.