Seasonal variation of total lipid and fatty acids of some freshwater fish living in Atatürk Dam lake

In this study, the sexual and seasonal variations in total lipid and fatty acid composition of total lipid, phospholipid and triacylglycerol fractions in muscle, liver and gonads of C. carpio, T. grypus and S. triostegus were investigated. Fish samples have been obtained from Atatürk Dam Lake in two-month periods between May 2008 and March 2009. The total lipid content varied seasonally from 0.53 % to 4.88 % in female muscles, 0.41 % to 5.31 % in male muscles, 0.54 % to 5.04 % in female gonads, 0.97 % to 4.62 % in male gonads, 0.74 % to 4.84 % in female livers, 0.50 % to 3.71 % in male livers of wet weight for C. carpio, T. grypus and S. triostegus. It was determined that muscles of T. grypus contained higher percentages of total lipid than S. triostegus and C. carpio.The total lipid amount in tissues of three fish species was influenced by reproduction period and season. For example, the total lipid content in muscles of female C. carpio and S. triostegus decreased to minimum in july after spawning. The amount of total lipid in livers of three fish species decreased in january and september. Total lipid content of liver was found higher than muscle in S. triostegus while total lipid content of liver was found lower than muscle in T. grypus. Total lipid content of gonads in both sexes of C. carpio and T. grypus increased in september.Fatty acid compositions of total lipid, PL and TAG fractions have been determined in muscle, gonad and liver tissues of fishes by gas chromatography using a mixture of fatty acid standards. The present study revealed that ?SFA, ?MUFA, and ?PUFA levels varied among fish species and tissues of the same fish species. The ?SFA and ?MUFA percentages of the total lipid extracted from tissues of the three fish species ranged from 24.02 % to 46.06 % and from 12.08 % to 46.83 %, respectively. The ?PUFA percentages of the total lipid in tissues was found from 21.55 % to 60.94 %. Generally, ?PUFA percentages of the total lipid in liver of three fish species were found higher than muscles of same fish species. The distributions of SFA, MUFA and PUFA proportions were found different among total lipid, PL and TAG fractions from lipids in tissues of C. carpio, S. triostegus and T. grypus in all seasons. Triaçilgliserol contained a lower proportion of PUFA and a higher proportion of MUFA and SFA than PL while PL contained higher proportion of PUFA than proportion of MUFA and SFA compared to TAG.According to the gas chromatography results, following saturated fatty acids: lauric acid (12:0), tridecanoic acid (13:0), myristic acid (14:0), pentadecanoic acid (15:0) palmitic acid (16:0), heptadecanoic acid (17:0) and stearic acid (18:0) monounsaturated fatty acids, palmitoleic acid (16:1n-7), oleic acid (18:1n-9) and eicosenoic acid (20:1n-9); and polyunsaturated fatty acids: linoleic acid (18:2n-6), linolenic acid (18:3n-3), eicosatrienoic acid (20:3n-3), arachidonic acid (20:4n-6), eicosapentaenoic acid (20:5n-3), docosapentaenoic acid (22:5n-3) and docosahexaenoik acid (22:6n-3) were determined in three tissues such as muscle, gonad and liver of fishes.The main constituents were 16:0 (15.61-31.83 % among SFA, and 18:1n-9 (8.83-33.64 %) among MUFA, 22:6n-3 (4.42-27.08 %) and 20:5n-3 (1.74-9.21 %) among PUFA in the total lipid extracted from tissues of three fish species in all seasons.The proportions of major fatty acids in tissues of C. carpio, T. grypus and S. triostegus varied to depending on reproduction period, temperature and season.It was found that the percentage of 16:0 in the total lipid extracted from muscles of both sexes of three fish species was higher in july and september than to other months while percentage of 22:6n-3 was found lower in may than to other months.The proportion of ?SFA and 16:0 in PL fractions of muscle lipids of C. carpio and T. grypus was found to be low in march in prespawning period whereas the proportion of ?SFA and 16:0 in three fish species found to be high september and november in postspawning.In this study, the n-3/n-6 ratio was determined to range from 1.15 to 4.05 for dorsal muscle, 1.30 to 3.50 for liver and 1.22 to 3.79 for gonads in total lipids in both sexes of all studied species. The higher n-3/n-6 ratio was found in muscle of T. grypus compared with C. carpio and S. triostegus.Triacylglycerol and PL fatty acid compositions in tissues of three fish species were found different. Triacylglycerols were characterized by a high content of MUFA, 16:0, 16:1n-7, 18:2n-6 and 18:3n-3; whereas phospholipids contained a large quantity of PUFA, mainly, 20:3n-6, 20:4n-6, 20:5n-3, 22:5n-3, 22:6n-3 and 18:0 among SFAs.