Beyond the Binary: Controlling Natural Sex-Change in Hermaphroditic Fishes

Abstract

Sex-change in hermaphroditic fishes is a complex but natural biological phenomenon that has significant implications for aquaculture fingerling production, selective breeding, and grow-out. Understanding the physiological, endocrinological, and molecular pathways underlying hermaphroditism in fishes offers unique opportunities to manipulate male-to-female and female-to-male transitions and maintain desired sex-ratios in hatcheries. Control over natural sex-change in hermaphroditic fishes can be achieved in vivo through socio-environmental manipulation, neuro-endocrine regulation, exogenous steroid treatment, or inhibition of aromatase activity with aromatase inhibitors (AIs). This review synthesises the current body of literature and knowledge of the tools associated with controlling sex-change, specifically in hermaphroditic fishes. Importantly, the recent advances in applying steroidal and non-steroidal hormones/compounds to control sex-change are described, as well as the effect of these approaches on gamete quality, fertility, and reproductive success of fishes in this unique group. Through investigating current practices and potential side-effects of controlling natural sex-change, we aim to guide the development of more effective and viable methods for maintaining desired sex-ratios in aquaculture selective breeding. This review highlights the need for further research to optimise control strategies, minimise unintended impacts, and promote best practices in controlling sex-change in hermaphroditic fishes.