Life cycle, abundance and transport of Calanus finmarchicus in Faroese waters

Calanus finmarchicus is the dominant copepod in the open ocean around the Faroe Islands. Measurements from 1990-93 showed that C. finmarchicus in the Atlantic Water outside the Faroe Shelf has two annual generations. The overwintering individuals migrate towards the surface in March-April and their spawning usually peaks in May. The majority of the individuals of this generation reaches stage CV in mid-summer. Some of the overwintering individuals remain in the upper layer and a small number of them spawn again in late summer. To the north of the Iceland-Faroes Front, C. finmarchicus has only one generation the overwintering individuals of which migrate towards the surface later than in the Atlantic Water and have their peak spawning in June. The individuals of this generation reach stages CIV and CV in August-September, when they migrate downwards.The phytoplankton biomasses in spring were higher north of the Iceland-Faroes Front than south of it. Therefore the delay of maturation and spawning north of the front cannot be explained by differences in food availability but probably by lower temperature or other hydrographic features.