Seasonal abundance and development of Calanus finmarchicus in relation to phytoplankton and hydrography on the Faroe Shelf

Calanus finmarchicus is almost absent from the Faroe Shelf during winter and is
advected into the shelf ecosystem during spring and summer. The species starts to spawn prior to the onset of the spring bloom. During the pre-bloom phase, reproduction is usually highest over the western and northern part of the shelf and the nauplii and copepodites are dispersed by the anticyclonic current throughout the shelf area. Gonad maturity evaluation revealed that females over the central shelf during 1997 were immature until early April, after which the proportion of mature females gradually increased and peaked at about 80–90% mature in May–June and August. Pre-bloom reproduction on the central shelf in 1997 was low and the recruits present then were most likely advected from the northern or western shelf. Two main periods with peaks of abundance were observed on the central shelf during 1997, the largest in May–June (ca 250 individuals m-3) and another in late August (ca100 individuals m-3). Off the shelf, the abundance of C. finmarchicus in most years was significantly
higher than on the shelf, and the proportional mix of stages differed.