Highlights

Abstract

Keywords

۱٫ The rationale and the early days

۲٫ The glorious seventies – The birth of our family

۳٫ From then onward

۴٫ GnRHs – The basic and the applied

۵٫ A few concluding thoughts

Acknowledgements

References

Abstract

Driven by the broad diversity of species and physiologies and by reproduction-related bottlenecks in aquaculture, the field of fish reproductive biology has rapidly grown over the last five decades. This review provides my perspective on the field during this period, integrating fundamental and applied developments and milestones. Our basic understanding of the brain-pituitary–gonadal axis led to overcoming the failure of farmed fish to ovulate and spawn in captivity, allowing us to close the fish life cycle and establish a predictable, year-round production of eggs. Dissecting the molecular and hormonal mechanisms associated with sex determination and differentiation drove technologies for producing better performing mono-sex and reproductively-sterile fish. The growing contingent of passionate fish biologists, together with the availability of innovative platforms such as transgenesis and gene editing, as well as new models such as the zebrafish and medaka, have generated many discoveries, also leading to new insights of reproductive biology in higher vertebrates including humans. Consequently, fish have now been widely accepted as vertebrate reproductive models. Perhaps the best testament of the progress in our discipline is demonstrated at the International Symposia on Reproductive Physiology of Fish (ISRPF), at which our scientific family has convened every four years since the grandfather of the field, the late Ronald Billard, organized the inaugural 1977 meeting in Paimpont, France. As the one person who has been fortunate enough to attend all of these meetings since their inception, I have witnessed first-hand the astounding evolution of our field as we capitalized on the molecular and biotechnological revolutions in the life sciences, which enabled us to provide a higher resolution of fish reproductive and endocrine processes, answer more questions, and dive into deeper comprehension. Undoubtedly, the next (five) decades will be similarly exciting as we continue to integrate physiology with genomics, basic and translational research, and the small fish models with the aquacultured species.

۱٫ The rationale and the early days
Growing up I was fascinated by the sea, and I always wanted to be a marine biologist engaged in research that would explore ocean life to the benefit of society. Following this childhood passion, I studied biology as an undergraduate and in 1974 I enrolled in an Oceanography MSc program, both at the Hebrew University of Jerusalem. At that time, we already knew that the world was headed for a major fishery crisis, as overfishing was rampant and marine/coastal pollution was adversely impacting the spawning grounds of many marine species. When it was time to choose my Master’s thesis research topic, I decided to pursue marine aquaculture, which back then was in its infancy. The first bottleneck to be resolved in finfish aquaculture was the inability of many commercially important marine fish to reproduce reliably when raised in captivity. The budding mariculture industry had to rely on harvesting wild juvenile fish or broodstock, transporting them to the farming operation and growing them to harvest size (for juveniles) or stripping them to obtain eggs and sperm for the production of fertilized eggs, larvae and juveniles (for broodstock). These were, of course, very unreliable and unpredictable practices, as wild juveniles/broodstock were only available seasonally for a limited time, and in some years they could not be found at all. This led me (and several others in the field) to study fish reproductive biology and endocrinology, with the eventual goal of enabling predictable reproduction in captive fish and closing their life cycles. We hypothesized that fish do not reproduce in captivity because they do not experience the conditions of a spawning ground, and that the absence of these environmental conditions, which are difficult/impossible to simulate in captivity, causes a hormonal failure that is responsible for the lack of captive reproduction.