Winter distribution of Calanus finmarchicus in the Northeast Atlantic

Data from plankton sampling and Optical Plankton Counter deployments during six cruises between December of 1994 and 1999 have been used to derive a c omposite three-dimensional distribution of the abundance of Calanus finmarc hicus during winter (December-January) in the Norwegian Sea and Northeast A tlantic. There are two centres of abundance, one in the eastern Norwegian S ea and Faroe-Shetland Channel, associated with the interface between Norweg ian Sea Deep Water and Intermediate Water layers, and another in the Irming er Sea southwest of Iceland in association with Labrador Sea Water. In the open Northeast Atlantic, the concentration of wintering animals is around 3 0% of that in the Norwegian Sea and the vertical distribution is more diffu se and on average deeper. Modelling studies have shown that the overwinter distribution and transport are key factors determining the spatial persiste nce of C. finmarchicus but, apart from the data presented here, there is li ttle knowledge of these large-scale properties.