The amino acid and fatty acid compositions of selected tissues of the dolphin fish ( Coryphaena hippurus) and their nutritional implications

Abstract

The amino acid and fatty acid compositions of muscle, gill, intestine, liver, ovaries, and whole bodies from captive juvenile and adult, and wild adult dolphin fish ( Coryphaena hippurus) were determined. Essential amino acid ratios ( A E ratios) of the whole body and individual tissues were calculated and compared. In addition, the concept of a metabolic A E ratio calculated from known daily protein turnover rates and from the amino acid profiles is introduced. Fatty acid profiles of phospholipid (PL) and triglyceride (TG) fractions in muscle and liver were also compared. There were few differences in the amino acid and fatty acid profiles of tissues between the different groups of dolphin fish examined. Linolenic series fatty acids were quantitatively the most important polyunsaturates in tissue PL fractions. C22: 6 n−3 was the major polyunsaturate present, accounting for approximately 20% of the total PLs in muscle and liver. There was no significant difference in tissue essential amino acid patterns between adult fish raised in captivity, and adult fish caught in the wild. However, the muscle of juvenile fish was lower in arginine and histidine contents than the muscle of adult fish. Ovaries had the lowest arginine, histidine, and tryptophan contents of all tissues measured. Calculated A E ratios of the muscle and whole body, and A E ratios based on the metabolic rates for protein turnover in muscle, gill, and intestine, were similar. All ratios predicted an ontological increase in dietary arginine, histidine, and tryptophan needs of dolphin fish consistent with the changes noted in tissue amino acid contents. It is concluded that the calculated A E ratios and fatty acid profiles of dolphin fish tissues may be useful guides in formulating diets for the culture of this species. The results obtained suggest that the requirements for arginine, histidine, and tryptophan may differ between subadult and adult fish. Dietary needs for linolenic series HUFAs, especially C22:6 n−3, are likely high throughout the life of this fish.