Effect of taurine enrichment in rotifer (Brachionus sp.) on growth of larvae of Pacific bluefin tuna Thunnus orientalis (Temminck & Schlegel) and yellowfin tuna T. albacares (Temminck & Schlegel)

To investigate the dietary effect of taurine on the larval stage of tuna species, Pacific bluefin tuna (PBF) and yellowfin tuna (YFT), larvae were reared until 16 days after hatching (dAH) and 14 dAH, respectively, and replicate samples were fed either non-taurine-enriched rotifers (T-0) or rotifers enriched with 800 mg taurine L−1 (T-800). Most PBF and YFT larvae were at the preflexion stage until 7 and 8 dAH, and there were no differences in the growth performance and total protein content of larvae between the T-0 and T-800 groups (t-test; P > 0.05). Thereafter, however, for larvae of both species, these parameters in the T-800 group significantly increased with enhanced notochord development compared to those in T-0 group (t-test; P < 0.05). Except for the RNA content in PBF larvae, there were no significant differences in changes of DNA and RNA content with larval growth between the T-0 and T-800 groups, but both PBF and YFT larvae showed increased protein DNA−1 and protein RNA−1 ratios in the T-800 group compared to the T-0 group after notochord flexion. This indicates that taurine is an important nutrient for the rapid growth of early stage PBF and YFT larvae, and we conclude that the growth improvement of PBF and YFT larvae by dietary taurine supplementation is due to the increase in protein synthesis efficiency after notochord flexion.