Fatty acid composition as indicator of food intake in cod larvae (Gadus morhua L.) from Lofoten, northern Norway

Abstract

The year class strength of the Arcto-Norwegian cod is mainly determined during the early life stages. The mortality is caused both by starvation and predation which are linked to environmental factors during this period. Stomach content analysis of first feeding larvae show that nauplii of Calanus finmarchicus is the most important diet. The larvae are, however, frequently found with "green gut" content. The fatty acid composition of lipids in marine animals reflects both the diets and bio-synthetic activities of the animals. The fatty acid composition of the most important prey items can be used as an indicator of the dietary lipids intake of the cod larvae. The fatty acids of total lipid were analysed from phytoplankton, eggs and nauplii of Calanus finmarchicus and cod eggs and larvae from Lofoten waters. Gas chromatographic and gas chromatographicmass spectrometric methods were used in the analyses. On the basis of these analyses we suggest that the lipids of phytoplankton form an important part of the diets of cod larvae during the first feeding period and that calanoid nauplii are more important at later larval stages.