Trouts are commonly farmed in many countries of the world. Minerals are required for normal life processes, and fish need these inorganic elements. Fish may derive these minerals from a diet and from ambient water. This study aimed to research differences in some of the mineral values in muscle tissues of diploid rainbow trouts (Oncorhynchus mykiss) cultured in freshwater and seawater. The study material consisted of twenty diploid rainbow trouts (Oncorhynchus mykiss), ten farmed in seawater and ten farmed in freshwater, with a weight of about 0.8-1 kg and average age of 17-19 months. Supernatant was prepared from muscle tissues of the fish. Concentrations of major minerals (Na, K, Ca, Mg, Cl, P) were investigated in supernatant from fish muscle tissues with an autoanalyzer. pH temperature, oxygen amount, salinity amount and saturation ratio of the trouts were found to be 8.40, 12 oC, 9.57 mg/dl, 18‰, 88.77% for seawater and 7.60, 11 oC 7.40 mg/dl, 0.68 ‰, 67.26% for freshwater fish. It was found that P, K and Mg levels in the muscle tissue of diploid rainbow trouts (Oncorhynchus mykiss) farmed in seawater were statistically significantly higher than in those farmed in freshwater (P0.05). This study showed that concentrations of minerals in trout muscle tissue can be affected by changes in water quality. It was concluded that muscle tissue of diploid rainbow trouts (Oncorhynchus mykiss) farmed in seawater is a better source of minerals in human diet than trouts farmed in freshwater.

25.4.2020