Variations in the quantity of zooplankton and the propagation of calanus finmarchius at station "M" in the Norwegian Sea, 1959-1966

1. From January 1959 to September 1966, 805 zooplankton samples were collected in vertical hauls from depths of 25-0 m, 100-0 m, and 600-100 m, at weather ship station "M" in the Norwegian Sea. The displacement volumes were measured, the developmental stage distribution of Calanus finmarchicus was determined, and the dominating species were noted. 2. Large seasonal and annual variations occurred in the volumes of zooplankton from the 100 to 0 m layer, while the volumes from the 600 to 100 m layer revealed considerable constancy. In 1965 and 1966 the plankton at station "M" appeared to be much richer and in 1961 somewhat poorer than the average for the period 1950-1966. The density of zooplankton in ml/m/ was very small in the 600 to 100 m layer while the 100 to 25 m and particularly the 25 to 0 m layer showed dense concentrations of zooplankton from April to August. 3. Calanus finmarchicus spawned in April and a second spawning of minor importance occurred in July-September