Optimization of stocking density and shipping duration for transportation of Pacific bluefin tuna, Thunnus orientalis (Temminck et Schlegel), eggs, and experimental verification of polyethylene glycol treatment to reduce collision damage

Abstract Pacific bluefin tuna (PBT), Thunnus orientalis, is one of the most important species for aquaculture worldwide. For the conservation of this species and sustainable development of the tuna farming industry, production based on closed‐cycle aquaculture should be promoted. In this study, to develop an efficient method for transporting PBT eggs, we simulated egg transportation to optimize stocking density and shipping duration, which are the two variables critical to the transportation procedure of PBT. Based on the findings of this study, we concluded that PBT eggs should be transported at a density of 1 × 104 eggs/L within 12 h in the field. Furthermore, we showed that collisions between eggs during transportation negatively affected the normal hatching rates of eggs, and polyethylene glycol (PEG) treatment (at 1000 μg/mL for 12 h) could reduce such damage. Our results suggest that PEG treatment is a practical approach that contributes to the stable transportation of PBT eggs, particularly in cases where the effects of physical shock damage is considerably increased.