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Changes in the Calanus complex

Changes in the Calanus complex on both sides of the Atlantic and its possible impact on fish populations

Project summary

A 10 degree latitude northward shift in the characteristic copepod populations of temperate oceans has been observed over the past several decades, seemingly in association with global warming effects on ocean water temperature. This has moved the Subarctic and Cold Temperate copepod species into the Arctic region replacing the dominant Arctic copepod Calanus finmarchicus with its similar sized conger C. helgolandicus. Thus, while during the 1960s and 70s, the distribution of C. helgolandicus showed a slight overlap in distribution with that of Atlantic cod, mainly in the Celtic Sea, Irish Sea, and southern North Sea, by the 1980s the latitudinal range of C. helgolandicus began expanding northwards and the southern limit of C. finmarchicus receded such that by the 1990s C. helgolandicus was more abundant than C. finmarchicus in the northern North Sea and west of Scotland.

Despite the similarity in size and the similar year to year total abundances of C. finmarchicus and C. helgolandicus dietary records of larval and juvenile cod show relatively few C. helgolandicus serve as prey. Thus, it is possible that a global warming-related change in the distribution and relative abundance of copepods will differentially impact the larvae of the fish species that feed upon them. As a result, marine scientists on both sides of the Atlantic are interested in characterizing changes to the Calanus complex (CC) and its possible impacts on fish populations. We request support to travel to Canada and the USA in order to establish the basis for a pan-Atlantic collaborative project on the CC complex.

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Funding agency: The Research Council of Norway
Project period: 2010
Project Leader: Howard Browman
Co- investigators: Anne Berit Skiftesvik, Stephane Plourde, Jeff Runge