Habitat related variations in fatty acids of catadromous Galaxias maculatus

The fatty acid profile of the galaxiid fish Galaxias maculatus (Salmoniform es) collected from an estuarine habitat (a river mouth), a freshwater creek and two land-locked freshwater lakes in Victoria, Australia, were investig ated with a view to evaluating habitat influences on the fatty acid profile . Fish from the freshwater creek were unpigmented, fresh-run juveniles (ref erred to as whitebait), the others adult fish. The fatty acids that predomi nated in adult G. maculatus muscle were 16:0 and 22:6(n-3), and 16:0 and 18 :1(n-9), respectively. In whitebait 22:6(n-3), 20:5(n-3) and 16:0 were pred ominant. Hopkins estuary fish had the highest amount of 18:2(n-6) but the l owest 18:3(n-3). In all galaxiid populations, polyunsaturated fatty acids ( PUFA) were the main group of fatty acids in total lipid in muscle, and acco unted for more than 40%, followed by saturates and monoenes. In landlocked populations, the amount of monoenes was lower than in other galaxiid popula tions. G. maculatus whitebait had significantly lower amount of saturates a nd the highest amount of n-3 fatty acids. The ratio of n-3 to n-6 PUFA rang ed from 4.6 (Hopkins estuary) to 7.6 (whitebait), and the former differed s ignificantly from all the other populations. The main fatty acids predomina ting in the liver of galaxiids from landlocked (Lake Bullen Merri) and estu arine populations were 16:0, 22:6(n-3) and 18: 1(n-9), and generally reflec ted the corresponding pattern in muscle. A principal component analysis of the fatty acid composition of muscle samples confirmed and highlighted the distinct fatty acid profile of the populations investigated, when three gro upings could be discerned. The study suggests that in addition to the diet, other habitat related factors may influence the fatty acid profile in cata dromous G. maculatus. (C) Ifremer/Elsevier, Paris.