Nutrient analysis and nutritional evaluation of fatty acid composition in three precious aquarium fishes

Anarrhichthys ocellatus, Arapaima gigas and Carcharias taurus are three precious fishes, the adults of which are cultured in some aquariums. However, the studies on the nutrient compositions for the adults of the three fishes are still limited. In this study, we measured the compositions of main nutrients (moisture, ash, crude protein and fat content) and fatty acids in muscle and liver tissues in adult A. ocellatus, A. gigas and C. taurus, and their corresponding feed, which were all collected from the aquarium. Furthermore, the correlation of fatty acid composition between the feed and tissues were calculated. The results showed that, the C. taurus had the highest crude protein content among the three fishes in muscle and liver, which was 26.84% and 24.03% respectively. A. ocellatus had the highest crude fat content among the three fishes in muscle and liver, which was 41.96% and 32.27% respectively. The ash content of muscle and liver in A. gigas was higher than the other two fishes, which was 4.95% and 5.51% respectively. The muscle and liver of C. taurus contained higher saturated fatty acids (SFA) content than the other two fishes, while A. ocellatus had higher monounsaturated fatty acids (MUFA) content than the other two fishes. Besides, A. gigas had higher amount of polyunsaturated fatty acids (PUFA) in muscle and liver and UFA/SFA ratio in muscle than the other two fishes. The correlation index showed that the fatty acids composition in feed and tissues (liver and muscle) obtained the highest similarity in C. Taurus. The correlation coefficient of fatty acid composition between feed and muscle and between feed and liver were 0.972 and 0.861, in C. taurus, respectively, and 0.912 and 0.846 in A. gigas, respectively, and 0.760 and 0.681, in A. ocellatus respectively. These results demonstrate that additional EPA and DHA could be supplemented in the feed of A. gigas, and additional MUFA should be added in the feed of A. ocellatus. For the first time, the present work presents the nutrient composition of the adults of the three precious fish species, and also provides valuable suggestions for the feed formulation in aquariums.