The Composition of Fatty Acids in Muscles of Six Freshwater Fish Species from the Mazurian Great Lakes (Northeastern Poland)

Lipid content and fatty acids composition of non-predatory fish: roach, Rutilus rutilus (L.), bream, Abramis brama (L.), vendace, Coregonus albula (L.), and of predatory fish: Eurasian perch, Perca fluviatilis L., pike, Esox lucius L. and burbot, Lota lota (L.) were examined. These fish were caught from three lakes of Mazurian Great Lakes (Kisajno, Dargin, Niegocin). The content of total lipid and some fatty acids varied widely within and among species. Generally, the lipid content was low (0.56-2.78%). Among the saturated and monounsaturated fatty acids, the predominant fatty acids were palmitic C16:0 (19.24-33.44%), stearic C18:0 (4.37-6.87%), palmitoleic C16:1 (4.51-12.93%), and oleic C18:1 n-9 (6.85-14.49%). Arachidonic C20:4 n-6 (3.17-6.55%), eicosapentaenoic C20:5 n-3 (4.14-8.91%), and docosahexaenoic C22:6 n-3 (5.91-24.67%) acids were the most abundant polyunsaturated fatty acids. In the case of all the freshwater fish, with the exception of bream, higher contents of saturated fatty acids than monounsaturated fatty acids were noted. Among the fish studied, the highest value of total n-3 polyunsaturated fatty acids (43.86%) was noted in vendace, whereas bream contained the highest content of total n-6 polyunsaturated fatty acids (11.21%). The ratio of n-3/n-6 ranged between 1.50 (burbot) and 4.40 (vendace). Differences in the content of fatty acids in fish with different feeding strategies (non-predatory and predatory) were measured. Non-predatory fish were found to have lower values of saturated fatty acids than predatory fish (P ≤ 0.05). Non-predatory fish contained significantly more eicosapentaenoic acid (EPA) than predatory fish (P ≤ 0.01), whereas the amounts of monounsaturated and n-3 and n-6 polyunsaturated fatty acids in non-predatory and predatory fish were not statistically significant (P > 0.05). The total n-3 polyunsaturated fatty acids was higher in non-predatory fish, but not statistically significant (P > 0.05). Similarly, the differences in DHA and n-3/n-6 ratio in muscles of predatory and non-predatory fish were not statistically significant (P > 0.05).