FATTY ACID COMPOSITION AND ω 3 / ω 6 RATIOS OF THE MUSCLE LIPIDS OF SIX FISH SPECIES IN SUGLA LAKE

Fatty acid composition of the muscle lipids of Carassius gibelio, Pseudophoxinus anatolicus, Sander lucioperca, Tinca tinca, Vimba vimba tenella and Capoeta capoeta in Sugla Lake were determined. In all species, palmitic acid (13.2518.54% of total fatty acids) and oleic acid (11.93-34.23% of total fatty acids) were identified as major saturated fatty acid (SFA) and monounsaturated fatty acid (MUFA), respectively. Docosahexaenoic acid (DHA) was found to be the major polyunsaturated fatty acid (PUFA) in T. tinca, C. capoeta, C. gibelio, P. anatolicus and S. lucioperca while the predominant PUFA of V. vimba tenella was eicosapentaenoic acid (EPA). S. lucioperca contained more ω3 fatty acids than the other fish species. The percentages of total ω3 fatty acids were higher than those of total ω6 fatty acids in all species. Since P. anatolicus is endemic and endangered, this species should be protected and produced for future marketing.


INTRODUCTION
Fish are a unique dietary source beneficial to human health.These valuable effects originate from ω3 polyunsaturated fatty acids, particularly the eicosapentaenoic acid (EPA) and DHA in the fish oil.Fish are a source of these ω3 fatty acids and are found abundantly in fish.
The quantities of EPA and DHA vary among and within a species according to environmental variables such as diet and whether fish are wild or farm raised (Kris-Etherton et al., 2002).DHA is recognized as a physiologically essential nutrient in the brain and retina for neural functioning and visual activity (Holub, 2001).Arachidonic acid and EPA are the parent compounds for the production of eicosanoids (Simopoulos, 2002).Additional health benefits from the consumption of fish or fish oil may be related to the PUFAs, especially ω3 PUFAs (Sidhu, 2003), which play a role in the prevention and treatment of heart disease, cancer, diabetes and inflammation (Atkinson et al., 1997;Connor, 2000;Hu et al., 2003).Long chain ω3 PUFAs cannot be synthesized by humans and must be obtained from the diet (Alasalvar et al., 2002).The valuable ω3 fatty acids are always present in fish flesh, even in lean fish (Ackman, 2002).
No reports have yet been published about the fatty acid composition of T. tinca (Linnaeus, 1758), V. vimba tenella (Nordmann, 1840), C. capoeta (Gueldenstaedt, 1773), C. gibelio (Bloch, 1782), P. anatolicus (Hanko, 1924) and S. lucioperca (Linnaeus, 1758) in Sugla Lake.As far as our literature survey could ascertain, there is no information on the fatty acid composition of P. anatolicus.The aim of this work is therefore to characterize and compare these species in terms of their fatty acid composition.

Area and sample collection
Sugla Lake is a freshwater lake in Konya, Turkey.It is a large lake in Konya Province, southwestern part of Turkey.It is located at around 37°20′15″N 32°01′56″E, and has an area of 25-80 km².Zengin et al. (2008) determined the irrigation water quality and pollutions of some lake and dams including Sugla Lake in Turkey.They reported that the water samples evaluated were suitable for irrigation with respect to certain parameters.Sugla Lake is also an important wetland site for birds.T. tinca, V. vimba tenella, C. capoeta, C. gibelio, P. anatolicus and S. lucioperca are the most abundant fish species in this lake.
C. gibelio, T. tinca, C. capoeta, P. anatolicus and V. vimba tenella are members of the family Cyprinidae.C. gibelio is a freshwater omnivore fish.P. anatolicus is a species of ray-finned fish.Its natural habitat is freshwater lakes and it is endangered EN B2ab (iii, iv, v) (Crivelli and Erk'akan, 2005).It is endemic to Anatolia-Turkey and it should be included into the national threatened fish category (Özuluğ and Öztürk, 2008).Capoeta spp. is an important freshwater fish species, which is widely found in Turkey (Geldiay and Balık, 2007).Tinca tinca and Vimba vimba are freshwater and brackish water fish, respectively.S. lucioperca is one of the most valuable freshwater carnivorous percid fish in Europe, not only as food, but also for sport (Schulz et al., 2008).In Turkey, especially in Central Anatolia, S. lucioperca is a commercial fish species.
T. tinca, V. vimba tenella, C. capoeta, C. gibelio, P. anatolicus and S. lucioperca were obtained from Sugla Lake in April.Ten individuals were sampled in each species for fatty acid analyses.All fish were almost the same size and age.Fish were transported in ice to the laboratory and dorsal muscle tissues were taken as samples.The samples were frozen at -26ºC until analyzed.At the beginning of analysis, the samples were allowed to equilibrate to room temperature.
Fatty acid methyl esters (FAMEs) were prepared from ten samples from each species.The FAMEs were analyzed on a HP (Hewlett Packard) Agilent 6890N model gas chromatograph (GC), equipped with a flame ionization detector (FID) and fitted with a HP-88 capillary column (100 m, 0.25 mm i.d. and 0.2 µm).Injector and detector temperatures were 240ºC and 250ºC, respectively.The oven was programmed at 160ºC initial temperature and 2 min initial time.Thereafter the temperature was increased to 185ºC at 4ºC/min, then increased to 200ºC at 1ºC/ min and held at 200ºC for 46.75 min.Total run time was 70 min.The carrier gas used was helium (1 ml/ min).GC analysis of FAMEs was performed in three replications.
Identification of fatty acids was carried out by comparing sample the FAME peak relative retention times with those obtained for Alltech (Carolean Industrial Drive, Satate Collage, PA) standards.Results were expressed as FID response area relative percentages.The results are given as mean ± SD in Table 1.

Statistical analysis
The results were submitted to analysis of variance (ANOVA), at 0.05 significance level, using SPSS 10.0.
The mean values were compared by Tukey's test.

RESULTS AND DISCUSSION
The fatty acid composition in the muscles of T. tinca, V. vimba tenella, C. capoeta, C. gibelio, P. anatolicus and S. lucioperca are presented in Table 1.Thirtyeight fatty acids were identified and evaluated in the fish samples.
DHA was the major fatty acid in S. lucioperca (22.48%) and C. capoeta (17.65%).Jankowska et al. (2003) stated that DHA in S. lucioperca meat is high and independent of the food DHA content.This fatty acid was determined as the predominant fatty acid in S. lucioperca (Jankowska et al., 2003;Özogul et al., 2007).Concerning C. gibelio, T. tinca and V. vimba tenella, oleic acid was the major fatty acid.Similarly, oleic acid was identified as the major fatty acid in Carassius carassius, in Porsuk Dam Lake, Turkey (Donmez, 2009) and in Vimba vimba tenella in Eğirdir Lake, Turkey (Kalyoncu et al., 2009).Oleic acid was also the predominant fatty acid in the cyprinid fish species, C. carpio (Donmez, 2009).In the present study, palmitic acid was the most abundant fatty acid in P. anatolicus.
EPA and DHA have beneficial properties for the prevention of human coronary artery disease (Leaf and Weber, 1988).In our study, among the ω3 series, S. lucioperca was a good source of EPA and DHA.EPA + DHA were 28.61, 20.62, 18.66, 18.20, 13.65 and 8.35% in S. lucioperca, C. capoeta, C. gibelio, P. anatolicus, T. tinca and V. vimba tenella, respectively.EPA + DHA were higher than that reported by Uysal et al. (2008) in C. capoeta capoeta, Donmez (2009) in C. carassius and Çelik et al. (2005) in S. lucioperca.This value was close to that reported for S. lucioperca (28.39%) in the Seyhan Dam Lake (Özogul et al., 2007) and in Beysehir Lake in autumn and spring (28.27-29.23%)(Guler et al., 2007), in Turkey.Similarly, Memon et al. (2010) determined that Indus river fish are a good source of ω3 fatty acids, particularly EPA and DHA, and should be recommended for dietary inclusion to reduce the risks of cardiovascular disease.

CONCLUSION
The fatty acid composition of six important fish species in Sugla Lake was determined and compared.S. lucioperca contained more ω3 fatty acids, which is important for human health, than the other fish species.The percentages of total ω3 fatty acids were higher than those of the total ω6 fatty acids in all species.S. lucioperca and C. gibelio may be a good dietary source of ω3 PUFA and ω3/ω6.Since P. anatolicus is endemic and endangered, this species should also be protected and produced for future marketing.

Table 1 .
Fatty acid composition (%) of six fish species muscle lipids in Sugla Lake t .
The data are presented as average values from three analyzed lots (means ± SD). y abc values for each sample with different letters in the same fraction are significantly different at p < 0.05.z SFA: Saturated fatty acid, MUFA: Monounsaturated fatty acid, PUFA: Polyunsaturated fatty acid. t