Nutritional condition of anchovy Engraulis encrasicolus larvae in connection with mesozooplankton feeding catabolism in the southern Bay of Biscay, NE Atlantic

The study examines the spatial variations over the French continental shelf of the southern Bay of Biscay (North-East Atlantic) in the nutritional condition of anchovy (Engraulis encrasicolus L.) larvae which was estimated through their DNA/C index. The same cruise yielded quantitative estimates of two metabolic descriptors of the functioning of mesozooplanktonic communities, the enzymes pyruvate kinase (PK) and trypsin, for the first time evaluated simultaneously. The aim was to appraise quality and quantity of matter assimilated by the mesozooplankton and to specify whether the main components of prey ingested by copepods are principally carbohydrates, through PK activity, or protein, under the action of the digestive endopeptidase trypsin. The larval DNA/C index was significantly correlated with PK specific activity but not with trypsin specific activity in the mesozooplankton. This is consistent with previous data on concomitant variations, although on quite different scales, in mesozooplankton PK activity and the larval DNA/C index.