MEPS 313:173-192 (2006)  -  doi:10.3354/meps313173

Ocean-scale modelling of the distribution, abundance, and seasonal dynamics of the copepod Calanus finmarchicus

Douglas C. Speirs1,*, William S. C. Gurney1,2, Michael R. Heath2, Werner Horbelt3, Simon N. Wood3, Beverly A. de Cuevas4

1Department of Statistics and Modelling Science, University of Strathclyde, Glasgow G1 1XH, UK
2FRS Marine Laboratory, PO Box 101, Victoria Road, Aberdeen AB11 9DB, UK
3Department of Statistics, University of Glasgow, Glasgow G12 8QQ, UK
4Southampton Oceanography Centre, Southampton SO14 3ZH, UK

ABSTRACT: The copepod Calanus finmarchicus is widely distributed over the sub-polar Atlantic and dominates the mesozooplanktonic biomass in that region. Despite this, all previous C. finmarchicus population modelling studies have been spatially and temporally limited. In this paper we present results from a fully stage-resolved model in a domain spanning the entire geographic range of the species (30 to 80°N and 80°W to 90°E. The model was driven by temperature and transport from the Ocean Circulation and Climate Advanced Modelling project (OCCAM) and phytoplankton food derived from satellite (SeaWiFS) sea-surface colour observations. The resulting quasi-stationary yearly cycle was assessed against seasonally resolved maps of continuous plankton recorder observations, winter cruise data on the distribution of diapausers, and time series from locations distributed over the North Atlantic. The model’s high computational efficiency permitted its free parameters to be selected to yield a good correspondence with the field data. We were also able to explore the effects of changing the assumptions regarding diapause and mortality. By falsifying alternative models we conclude that (1) a fixed fraction of each surface generation enters diapause, (2) overwintering individuals enter diapause at the end of the fifth copepodite stage, and (3) mortality is an increasing function of temperature. Finally, we demonstrate that the demographic impact of transport is limited, except in shelf seas and at the edges of the distribution; nevertheless, there is a very high level of population connectivity over the whole domain.

KEY WORDS: Calanus finmarchicus · Structured population model · Diapause · Temperature-dependent mortality · CPR · OCCAM · SeaWiFS

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