Variations in the fatty acids compositions of muscle tissue, due to starving and feeding Cyprinion macrostomus (Heckel, 1843) at 35 and 24°C which naturally lives at 35±0.5°C in the Kan-gal Thermal Spring (Sivas) were investigated. No qualitative variation took place in the fatty acid composition of the fish which were fed and star-ved at 35°C. As far as the fish which were fed and starved at 24°C were concerned, it has determi-ned that docosapentaenoic acid (C22:5) and docosahexaenoic acid (C22:6), which are not found in fo-od could be synthesized and linoleic acid (C18:2) percentage was drastically decreased. According to the results, it can be concluded that the most changes took place in the long chain high unsaturated fatty acids at 35 and 25°C (C18:2, C18:3, C20:3, C22:4, C22:5, C22:6). It is known that the repro-duction of C. macrostomus living at 35°C in the Kangal Thermal Spring is not very productive. It has been shown that under controlled temperature at 24°C, these fish could synthesize polyunsaturated fatty acids. The synthesis of these fatty acids at the latter temperature could be an indicator of higher rate of reproduction of the fish.

Variations in the fatty acids compositions of muscle tissue, due to starving and feeding Cyprinion macrostomus (Heckel, 1843) at 35 and 24°C which naturally lives at 35±0.5°C in the Kan-gal Thermal Spring (Sivas) were investigated. No qualitative variation took place in the fatty acid composition of the fish which were fed and star-ved at 35°C. As far as the fish which were fed and starved at 24°C were concerned, it has determi-ned that docosapentaenoic acid (C22:5) and docosahexaenoic acid (C22:6), which are not found in fo-od could be synthesized and linoleic acid (C18:2) percentage was drastically decreased. According to the results, it can be concluded that the most changes took place in the long chain high unsaturated fatty acids at 35 and 25°C (C18:2, C18:3, C20:3, C22:4, C22:5, C22:6). It is known that the repro-duction of C. macrostomus living at 35°C in the Kangal Thermal Spring is not very productive. It has been shown that under controlled temperature at 24°C, these fish could synthesize polyunsaturated fatty acids. The synthesis of these fatty acids at the latter temperature could be an indicator of higher rate of reproduction of the fish.