Application of the plankton-kreisel tank for small-scale larviculture of Pacific bluefin tuna Thunnus orientalis

Genome editing by manipulating the embryos of Pacific bluefin tuna (PBT) was recently proposed for improving the breeding and aquaculture production of PBT. However, the yield of genome-edited eggs is limited due to the narrow timing of genome editing of embryos and the labor-intensive process. Therefore, the development of a small-scale larviculture method is necessary for efficient evaluation of the phenotype and traits of genome-edited PBT larvae. The plankton-kreisel tank can form a vertical rotating flow that may prevent the sinking syndrome of PBT larvae. In this study, we applied a plankton-kreisel tank (8-L) for PBT larviculture up to 10 days post-hatch (dph). We compared the survival rate and growth of PBT larvae reared in the 8-L plankton-kreisel tank and an 8-L cylindrical tank (CT). The survival rate in the plankton-kreisel tank at 10 dph (58.9 ± 4.8%) was significantly higher than that in the CT (4.8 ± 3.6%). Larval growth was not significantly different between these tanks. We observed that the larvae that sank to the tank bottom drifted with the strong vertical rotating flow along the tank wall during the night. This flow in the plankton-kreisel tank prevents the sinking syndrome. Thus, this apparatus is proposed for small-scale larviculture experiments in PBT.