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The partitioning of free amino acids between phytoplankton, zooplankton and ichthyoplankton in the Ushant region
V. Martin-Jézéquel, P. Camus and S.A. Poulet

The concentration of 20 free amino acids (FAA) was investigated in extracts of naturally occurring seston (< 500 mm), and from stomachs (midgut) of two species of pelagic fish post-larvae (4-15 mm): Scomber scombrus L. and Trachurus trachurus L. Samples were collected in July 1986 from thermally stratified waters off Ushant. Their total concentration varied in relation to the size of the particles and post-larvae, and the time and depth of sampling. Good correspondence can be found between FAA quantity in the midguts of the larvae and the localisation of both prey and predators. The major amino acids in seston were glutamic acid, glycine, serine and taurine. The most abundant amino acids measured in the midguts of the post-larvae of both species were glycine, arginine, alanine, taurine, leucine, valine, ornithine and lysine. According to the determination of prey in midgut contents, the partitioning of amino acids in phytoplankton, zooplankton and fish larvae demonstrated that zooplankton (copepods) were the main source of FAA in the midguts of the fish larvae; but the different composition of FAA found in the midguts during the diurnal cycle cannot be related to the variations of feeding activity of the post-larvae.

Keywords: free amino acids, plankton, fish nutrition.
Contents of this volume Sci. Mar. 53(2-3) : 259-268 Back PDF
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