Investigation of the lipid and fatty acid content and composition of barramundi (Lates calcarifer) from fresh and saltwater regimes was carried out to provide preliminary information on possible variability of these parameters associated with environment.
Oil content of the flesh ranged from 384-1009 mg/100 g (wet weight) and is in the low-mid oil range for Australian fish. With the exception of the Pascoe River sample, freshwater fish have higher lipid content than the saltwater fish. In addition, freshwater fish contained considerably higher relative levels of the storage lipid triacylglycerol (mean 51%). Based on oil content and TAG level, the saltwater specimen from Pascoe River is more similar to the three freshwater fish analysed.
Major fatty acids in barramundi were 16:0, 18:1w9c, 18:0, 22:6w3, (docosahexaenoic acid, DHA) and 20:4w6 (arachidonic acid, AA). Less abundant components included 18:2w6 (linoleic acid, LA), 16:1w7c, 20:5w3 (eicosapentaenoic acid, EPA), 18:1w7c and 22:5w3 (docosapentaenoic acid, DPA). EPA and DHA are the essential omega-3 fatty acids. Freshwater fish have higher relative levels of LA, 18:1w9c, 16:1w7c, 18:1w7c, 18:3w3, 14:0 and lower EPA and DHA than the saltwater fish. The greatest difference between the fresh and saltwater samples for any single fatty acid was observed for DHA (5% freshwater; 18-25% saltwater, excluding the Pascoe River fish – specimen #2). The ratio of w6 PUFA/w3 PUFA differs significantly between salt (0.43-0.67, excluding specimen #2) and freshwater (1.3-2) fish. Saltwater fish contained higher absolute amounts of DHA and cholesterol, whilst freshwater fish showed a higher AA content. In comparison to other Australian seafood, barramundi contains reduced amounts of PUFA. However, the low oil content combined with high relative levels of w3 PUFA in saltwater fish and both w3 and w6 PUFA in freshwater fish are nutritionally attractive features.
The results of this preliminary study also suggest that it may be possible to use fatty acid profiles to ascertain the environment in which collected specimens have recently been feeding.
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