Abstract
Changes in nutritional constituents and enzyme activities were clarified in yellowfin tuna (YFT, Thunnus albacares) eggs during embryonic development, from eggs immediately after fertilization to hatching. The protein levels in the eggs gradually increased with development until the completion of hatching. In contrast, the triglyceride (TG) and free amino acid (FAA) levels in the eggs gradually declined with embryonic development until hatching was complete, although the energy composition of the FAAs was lower than that of the TGs throughout embryonic development. These results indicate that endogenous TGs are preferentially expended as an energy source during embryonic development. Overall, changes in the activities of aspartate aminotransferase, alanine aminotransferase, creatine kinase, and alkaline phosphatase showed similar patterns throughout development. First, the enzyme levels diminished; then, they remained at constant, low levels just before hatching, when they rapidly increased. This rapid increase was consistent with the protein content, suggesting that organ differentiation and functionalization were promoted during this period. These results will contribute to the establishment of mass-seeding production of YFT.
Highlights
Published: 11 March 2022Yellowfin tuna (YFT, Thunnus albacares) is one of the most-caught fish and is a commercially important species in Central and South American countries, including Panama, Mexico, Ecuador, and Venezuela [1]
50% hatching (50H), and HC (0, 1.1, 3.6, 5.3, 7.3, 12.1, 16.3, 18.3, and 20.1 h, respectively); and changes in the dry egg and larval weights were recorded over the course of embryonic development
The changes in nutritional constituents were clarified in YFT eggs and Inhatched this study, the during changesembryonic in nutritional constituents clarified inprogressed, YFT eggs and newly larvae development
Summary
Yellowfin tuna (YFT, Thunnus albacares) is one of the most-caught fish and is a commercially important species in Central and South American countries, including Panama, Mexico, Ecuador, and Venezuela [1]. In the eastern Pacific, the tuna catch increased from about 0.1 million tons in 1960 to over 0.4 million tons in. Various studies have reported on the captive propagation of YFT [3–5], the food selectivity of larvae [6,7] age validation and growth and survival [8,9], the enzyme activities and amino acid composition of early juveniles [10], and the optimum water-quality parameters for larval growth [11]. High mortality at the larval and early juvenile stages was shown by Lang et al [12] and Kaji et al [13,14] for both YFT and Pacific bluefin tuna (PBT, Thunnus orientalis) [15,16].
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