Growth is one of the most desirable traits in an aquaculture species, which is in turn closely related to early maturity, a complex biological process that reduces the final yield of fish farming operations. Thus, while the selection of rapid-growth fish is highly attractive for the aquaculture sector, it is also common to select against early-maturing fish. The correlation between body size and age at maturation is still not entirely understood in fish, and several studies have reported different associations between the two traits. In this study, biometric and physiological parameters are being evaluated in order to determine the relationship of small and large sized female sea bass and its ovarian growth. Fish were individually tagged and growth and gonadal development were evaluated during the second and third year of age. Fish have been sacrificed at the end of each sexual cycle and performance indicators are being restored to specific point-in time based on the oocyte development. Temporal hormonal profiles, including Fsh, sex steroids, vitellogenin and Igf-1 plasma levels are being determined. Furthermore, genes with a putative role in the relationship between both growth and reproductive systems will be analysed. Results show the existence of early differential growth within the female sea bass. Thus, slow- (small-sized) and fast- (large-sized) growing female sea bass have been identified and their relationship to gonadal maturity has been considered. We have identified four female phenotypes as follows: a) small-sized and immature gonads, b) small-sized and maturing gonads, c) large-sized and immature gonads and d) large-sized and maturing gonads, over the second and third sexual cycles of this species. Accordingly, physiological aspects and also molecular factors are being considered to elucidate key events contributing to the relationship between these traits. A comprehensive understanding of the relationship between growth and maturation in sea bass will contribute to gain new insights for improving breeding conditions and production of this teleost species.

Project funded from the Ministry of Science and Innovation (AGL2016-75400, PID2019-109548RB-I00). L.S. supported by a FPI fellowship from MICINN (Spain).

Resumen del trabajo presentado en 6th Genomics in Aquaculture Symposium, celebrado en Granada (España) del 04 al 06 de mayo de 2022.