Five years of optimizing the assisted reproduction protocol for European eel: What worked and what didn’t?

Summary

The production cycle of the European eel needs to be closed in order to supply aquaculture with juvenile glass eels and to alleviate fishery pressure on the natural population, thereby contributing to its recovery. Currently, we are able to produce larvae batches three times per week. Over the past five years we have executed experiments aiming to condition glass eels into high quality brood stock females and optimize the artificial reproduction protocol. Feminization of young juveniles contributes to shortening the generation time at least 5-fold. Simulated migration induces early sexual maturation. Steroid implants containing 17 methyltestosterone (17MT) and 17β estradiol (E2) induce the more advanced maturation stages and shorten the stressful period of weekly carp pituitary extract (CPE) injections to fully mature females. Instead of using CPE, stable eel-specific recombinant gonadotropins have been successfully applied to produce eel larvae.