## 3 Results and Discussion
In all of the experimental fish groups, the pattern of accumulation of Ax and Cx was constant: the amount of Ax was always greater than that of Cx (Table 2), and the correlation between their concentrations was very high. The coefficients of the Pearson correlation were higher than 0.99 for all of the tested organs (gonads and liver) of fishes from the groups bred under no-Mz-containing environmental conditions (Figures 5 and 6) and 0.9738 for all of the measured samples in the third fish group (Figure 7), where the specimens were bred in an environment containing permitted levels of MZ during the 60 d period. The accumulation of Ax and Cx in the control fish group was the most significant in the female gonads, followed by the accumulation in the male gonads, and it was the lowest in the liver (Table 2). The fish were fed with a conventional diet. These fish species are able to absorb and cumulate Ax and Cx regardless of xanthophyll content in concentrations under the detection limit [19]. Similar results obtained in an earlier study by our team were collected: 0.176 and 0.141 mg/kg were the mean contents of Ax and Cx in Salmonella eggs, respectively [25]. Due to their antioxidant potential and reproductive syndrome M74 prevention, other authors determined the content of both pigments in Salmonella eggs [3]. In addition, [PERSON] and [PERSON] suggested a concentration limit of 2.22 mg/kg in order to prevent or overcome this early mortality syndrome [38]. The determination of the main carotenoids with such prevention potential in different organs of Salmonidae can assist  
Figure 4: Typical chromatogram of sample solution of liver. the clarification of the bio-ability, some physiological processes during feeding, and their health status. Figure 5: Pearson correlation between Ax and Cx accumulation in the female gonads of rainbow trout, _O. mykiss_. Figure 6: Pearson correlation between Ax and Cx accumulation in the male gonads of rainbow trout, _O. mykiss_. During sexual maturation and spawning migration, Ax is mobilized from the muscle to the skin and gonads [39; 40]. This confirms the xanthophyll quantities accumulated and determined in the present study: the fish species were in the breeding season, and the highest concentration levels of Ax and Cx were determined in the gonads. The female gonads contained higher concentrations of Ax and Cx than the male gonads. The females accumulate these pigments in the eggs, avoiding the early mortality of their offspring. This natural phenomenon is explained by the fact that each species primarily provides resources for its reproduction and therefore for the survival of the species. The stockpiling of xanthophylls in trout eggs is an effective instrument for naturally overcoming the reproductive syndrome M74 and the early mortality of their offspring [3; 20]. These powerful antioxidants have been shown to counteract thiamine deficiency and protect post hatch embryos and fry from a range of negative effects of this reproductive disorder until the yolk sac has been completely resorbed. Low concentration levels of thiamine and xanthophylls in fish eggs result from an insufficient dietary intake of the females [20]. Analogous results were obtained for the second fish group. The specimens were bred under no-Mz-containing environmental conditions with a xanthophyll-supplemented diet. The highest Ax and Cx concentration levels were determined in the order of female gonads, male gonads, and liver (Table 2). A xanthophyll accumulation rate for the third experimental group was established. The specimens were bred in an environment containing MZ at permitted levels. These conditions led to low accumulation levels of Ax and Cx in the gonads and liver, regardless of the xanthophyll-supplemented diet (Table 2). Another tendency was confirmed: the accumulation rate of Ax and Cx in the gonads was highest in the second experimental group. However, the highest xanthophyll levels in the liver were found in the samples of the third experimental group.