Evidence suggests that differences in fatty acid composition among various fish species may be due to differences in diet or to environmental factors such as temperature, salinity, and depth at which the fish are caught. The beneficial effects of a diet containing fish on cardiovascular or other diseases have been associated with their high content of eicosapentaenoic (20:5n-3) and docosahexaenoic (22:6n-3) acids. In this study we analyzed the fatty acid composition of the flesh of 18 different species of marine fish and of cultured rainbow trout. The fish were obtained from the Black and the Marmara Seas, both of which have unique biological and ecological systems as well as eutrophication and pollution. The contents of 20:5n-3 and 22:6n-3 in the marine fish ranged from 4.2 to 13.3 wt% of total fatty acids, and from 6.6 to 40.8 wt%, respectively. The most important differences from other studies on oceanic fish were the tendencies toward higher percentages of 16:0 and 22:6n-3. The n-3 series of polyunsaturated fatty acids were present as 32.4+/-1.9% of the total fatty acids. The present study suggests that mature and immature Pomatomus saltator as well as Engraulis encrasicolus, Mullus surmuletus, Sardina pilchardus, Mugil cephalus, and Sarda sarda may be preferred for the Turkish diet as a result of their high 20:5n-3 and 22:6n-3 contents. The cultured rainbow trout Oncorhynchus mykiss is not as good a source of n-3 fatty acids as are the marine fish.

Original article Effects of differences in diet and seasonal changes on the fatty acid composition in fillets from farmed and wild sea bream (Sparus aurata L.) and sea bass (Dicentrarchus SummaryThe effects of dietary fatty acids and seasonal variation on the fatty acid profiles of farmed and wild sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) were determined by analysis of their fillets. Farmed sea bream and sea bass were fed on the same commercial feeds all year. Fatty acid profiles in the fillets reflected the fatty acid profiles of the commercial feeds. The predominant fatty acids in the trial feeds, fillets of farmed and wild sea bream and sea bass were 16:0, 18:1n-9, 18:2n-6, 20:5n-3 and 22:6n-3. The fatty acid profiles in the fillets of farmed sea bream and sea bass did not differ (P > 0.05) except in the winter season compared with those of their wild counterparts. However, the content of eicosapentaenoic acid (20:5n-3), docosahexaenoic acid (22:6n-3) in the fillets of the farmed and wild sea bass were significantly (P < 0.05) higher than the farmed and wild sea bream. The wild sea bream had significantly (P < 0.05) higher total saturated fatty acid and monounsaturated fatty acid (MUFA) levels, and lower total n-6 and n-3 polyunsaturated fatty acid (PUFA) levels in winter than in the summer and spring seasons. Similarly, in the fillets of wild sea bass, total n-3 PUFA levels were significantly (P < 0.05) lower, and the MUFA levels were higher in winter than in the other seasons. These results indicate that the farmed fish fillets were good sources of n-3 PUFA in each of the three seasons. However, wild fish were good sources of n-3 PUFA in the spring and summer.Keywords Diet, farmed and wild sea bream and sea bass, fatty acid, season.

The muscles and livers of the ten rainbow trouts ( Oncorhynchus mykiss; N, 1752) obtained from Sapanca, Aquaculture Facility of Aquatic Products Faculty, The University of Istanbul (Turkey), have been analysed quantitatively for some minor elements using the radioisotope energy dispersive X-ray fluorescence (EDXRF) and neutron activation analysis (NAA) methods. It was found that samples contain Na, K, Ca, Sc, Cs, Fe, Co, Cu, Zn, Se, Br, Rb, Sr, Au, La and Ce in different amounts. Comparison of the results with those of reference river fish samples indicated that agricultural rainbow trout samples from Sapanca region have higher Fe level.