Changes in the nutritional composition and organ-specific enzyme activities of laboratory-reared bluefin tuna Thunnus orientalis larvae and early juveniles
2019
Tanaka, T. (Kindai University, Higashimuro, Wakayama (Japan). Aquaculture Research Institute) | Oku, K. | Honryo, T. | Takaoka, O. | Biswas, A.K. | Takii, K.
The Pacific bluefin tuna Thunnus orientalis (PBT) is an important food resource species in aquaculture. To evaluate somatic growth, it is important to understand the nutrition and organ development of larval and juvenile fish. In the present study, we examined nutritional composition and organ-specific enzyme activity of laboratory-reared PBT during early development. Experimental fish were reared at the Kindai University Fish Nursery Centers at Wakayama, Japan. Sampling was carried out from 0-32 days after hatching (DAH). At 15 DAH, the standard length and wet body weight rapidly increased, reflecting the completion of morphological change from the flexion to the postflexion phase. Although the moisture content (%) gradually decreased, the protein contents (%) increased during development. Fat, glycogen, and ash contents did not increase as much as protein content, suggesting that the decremental moisture content was mainly replaced with protein content. In addition, the activity of bone-specific alkaline phosphatase, a bone formation marker, was higher than that of tartrate-resistant acid phosphatase, a bone resorption marker. We assume that bone mineralization is promoted in the early life stages of PBT through the activation of bone formation. These data will contribute to the development of suitable rearing technologies for the mass production of PBT fingerlings.
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