Using osmotic pumps to deliver hormones to induce sexual maturation of female Japanese eels, Anguilla japonica

► Vitellogenesis in eels was completed after implanting an osmotic pump loaded with SPE. ► Implantation of an osmotic pump loaded with hCG inconsistently induced early vitellogenesis. ► The GnRHa pump implantation exhibited no stimulatory effect. ► Egg quality was similar for both osmotic pump and injection groups.