Early ontogeny-related changes of the fatty acid composition in the Percichthyid fishes trout cod, Maccullochella macquariensis and Murray cod, M-peelii peelii

Changes in the fatty acid profiles of the Percichthyid fish trout cod, Macc ullochella macquarlensis (Cuvier), and Murray cod, M. peelii peelii (Mitche ll), two Australian native freshwater fish species, were investigated durin g early development from egg to yolk-sac-resorbed larval stage. In the two Percichthyid fishes polyunsaturated fatty acids (PUFA) accounted for more t han 50% of the 19 quantified fatty acids in total lipid. The fatty acids th at occurred in the highest abundance in both trout cod and Murray cod, in a ll developmental stages, in order, were docosahexaenoic acid [DHA 22:6(n-3) ], arachidonic acid [AA 20:4(n-6)], oleic acid [18:1(n-9)] and palmitic aci d (16:0), all of which exceeded 100 mu g per mg total lipid in most instanc es: The ratio of 22:6(n-3) to eicosapentaenoic acid-20:5(n-3) in eggs of tr out cod and Murray cod was 5.4:1 and 7.3.1, respectively, and remained almo st unchanged through development, and was considerably higher than the 2:1 ratio generally reported for fish eggs. In trout cod, 11 of the 19 fatty,ac ids in total lipid decreased during the transformation from egg to yolk-sac -resorbed larva. In Murray cod, only 16:1(n-7) showed a significant decreas e whilst 20:4(n-6) increased significantly with development. Overall, there was a tendency in both species to conserve n-3 and n-6 series highly unsat urated fatty acids (HUFA), suggesting their essentiality in first feeding l arvae. These observations are discussed in relation to the feeding habits o f trout cod and Murray cod, which are top order, freshwater carnivores. (C) Ifremer/Cnrs/Inra/Lrd/Cemagref/Elsevier, Paris.