The effect of dietary DHA and taurine on rotifer capture success, growth, survival and vision in the larvae of Atlantic bluefin tuna (Thunnus thynnus)

During the egg and yolk sac larval stages, there was a significant decrease (P < 0.05) in SAT, MONO and PUFA that can be expressed as 46.7%, 50.3% and 57.1%, respectively. Similarly, the levels of DHA, EPA, and ArA were markedly (P < 0.05) reduced that can be expressed as 59.8%, 52.5% and 59.5%, respectively. In the DHA study, there was a rotifer DHA dose dependent (P < 0.05) effect on prey consumption by 3-7 dph ABFT larvae where the highest DHA level (11 mg g− 1 DW rotifer) elicited significantly (P < 0.05) higher rotifer consumption compared to the control and moderate DHA diets (2 mg g− 1 DW and 5 mg g− 1 DW rotifer, respectively). Moreover, larvae with the highest DHA level (7.01 mg g− 1 DW) exhibited a significantly (P < 0.05) higher opsin protein concentration (25.27 unit area− 1) compared to the 2.83 mg DHA g− 1 DW and 1.26 mg DHA g− 1 DW fish (20.32 and 16.33 opsin protein unit area− 1, respectively). Although there was a significant (P < 0.05) taurine modulated increase in larval length in 10 dph fish, there was a non-significant (P > 0.05) growth advantage, in terms of dry weight, as a result of moderate dietary taurine supplementation at the end of the study. Nevertheless, the moderate 6.44 mg taurine g− 1 DW larvae exhibited markedly (P = 0.024) better survival and > 4 times higher (P = 0.0018) average tank biomass (273.6 mg) than the low (1.97 mg g− 1 DW) and high (12.62 mg g− 1 DW) taurine fish (62.14 and 56.90 mg, respectively). Overall, the data suggests that supplementing effective levels of DHA and taurine contributes to an array of physiological processes resulting in enhanced vision and prey acquisition to markedly improve ABFT larval performance during early development.