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

¹ School of Ecology and Environment, Deakin University, P.O. Box 423, Warrnambool, Victoria 3280, Australia
² Marine and Freshwater Resources Institute, Snob's Creek, Private Bag 20, Alexandra, Victoria 3714, Australia

Received: 14 December 1998
Accepted: 6 April 1999

Abstract

Changes in the fatty acid profiles of the Percichthyid fish trout cod, Maccullochella macquariensis (Cuvier), and Murray cod, M. peelii peelii (Mitchell), two Australian native freshwater fish species, were investigated during early development from egg to yolk-sac-resorbed larval stage. In the two Percichthyid fishes polyunsaturated fatty acids (PUFA) accounted for more than 50 % of the 19 quantified fatty acids in total lipid. The fatty acids that occurred in the highest abundance in both trout cod and Murray cod, in all 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 acid (16:0), all of which exceeded 100 μg per mg total lipid in most instances. The ratio of 22:6(n-3) to eicosapentaenoic acid-20:5(n-3) in eggs of trout cod and Murray cod was 5.4:1 and 7.3:1, respectively, and remained almost 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 acids 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 decrease 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 unsaturated fatty acids (HUFA), suggesting their essentiality in first feeding larvae. These observations are discussed in relation to the feeding habits of trout cod and Murray cod, which are top order, freshwater carnivores.