Journal Article

Variability in retention of <i>Calanus finmarchicus</i> in the Nordic Seas

Thomas Torgersen and Geir Huse

in ICES Journal of Marine Science

Published on behalf of ICES/CIEM

Volume 62, issue 7, pages 1301-1309
Published in print January 2005 | ISSN: 1054-3139
Published online January 2005 | e-ISSN: 1095-9289 | DOI:
Variability in retention of Calanus finmarchicus in the Nordic Seas

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  • Environmental Science
  • Marine and Estuarine Biology


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Using a regional ocean circulation model and particle tracking, we have studied the probability of the copepod Calanus finmarchicus being retained within the Nordic Seas' population as a function of its initial location, its vertical migration pattern, and the interannual variability in physical forcing. Defining a retention index in terms of the number of particles remaining within the Nordic Seas divided by the initial number of particles released, we found that spatial location had the greatest effect on the retention index during the study period, 1988–1991. Variability as a result of differences in physical forcing among years and among different seasonal vertical migration patterns had smaller but similar effects. The seasonal vertical migration behaviours with the highest advective loss rates and the most sensitive to interannual physical forcing were those that ascended early and descended late from a shallow summer depth. Average retention within the Nordic Seas was 0.40 after one year in simulations with diffusion and advection, and 0.42 in simulations with advection only. The average retention at the end of the four-year sequence was 0.10 and 0.12 with and without diffusion, respectively. Particles located in the western areas of the Nordic Seas had the highest retention, while those along the Norwegian coast showed little or no retention after four years. Initial location has a larger influence on retention than interannual variability in advective fields. C. finmarchicus offspring tend to reside in areas different from their parents, with different probabilities of retention. This spatial variability in retention rate is also experienced as inter-generational variability by members of the population. Model results suggest that almost all of the C. finmarchicus that are advected into the Barents Sea originate from off the Norwegian coast. Thus, predicting C. finmarchicus inflow into the Barents Sea requires knowledge of their abundance on the Norwegian Shelf.

Keywords: Barents Sea; Calanus finmarchicus; models; Norwegian Sea; ocean circulation; particle tracking; retention

Journal Article.  5327 words.  Illustrated.

Subjects: Environmental Science ; Marine and Estuarine Biology

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