Eastern little tuna,Euthynnus affinis(Cantor, 1849) mature and reproduce within 1 year of rearing in land-based tanks

Abstract

Eastern little tuna (ELT, Euthynnus affinis) is expected to see use as a novel aquaculture species due to its rapid growth and high economic value. In this study, closing of the complete life cycle of ELT in land-based tanks was successfully carried out. Seed production of a first generation (F1) derived from wild-caught ELT broodstock was conducted in 2010, 2011 and 2012. Survival percentages of F1 ELT at 365 days post hatching for the 2010, 2011 and 2012 year classes were 0.9%, 0.4% and 6.3% respectively. On average, F1 ELT were approximately 40 cm in total length and weighed 1500 g by the time they reached 1 year of age. Successful artificial induction of spawning was achieved in 1-year-old F1 ELT using a gonadotropin-releasing hormone analogue (GnRHa). Induction of spawning was successful at the first administration of GnRHa in the 2010, 2011 and 2012 year classes. First spawning was observed at 4 or 5 days post implantation, which indicated that oogenesis and spermatogenesis progressed within 1 year of rearing in land-based tanks. During spawning periods, the average number of fertilized eggs and the average number of hatched larvae per spawning event in the 2010, 2011 and 2012 year classes were 20,480 eggs day−1 and 177 larvae day−1, 39,423 eggs day−1 and 9347 larvae day−1, and 819,555 eggs day−1 and 674,445 larvae day−1 respectively. Therefore, it was concluded that both male and female ELT reared in land-based tanks were capable of reproduction at 1 year of age.