Editorial: Reproductive biology of commercially important marine fish species

Sustainable fisheries and successful aquaculture both depend fundamentally on a deep understanding of reproductive biology. In commercially important marine fish species, reproductive traits such as age and size at maturity, spawning seasonality, sex differentiation, energy allocation strategies, and environmental control of gametogenesis directly shape population resilience and production efficiency. As fishing pressure intensifies and aquaculture expands to meet global seafood demand, research that clarifies these processes becomes increasingly essential.The contributions assembled in this Research Topic collectively highlight how reproductive knowledge underpins stock assessment, hatchery optimization, broodstock management, and long-term sustainability. By integrating long-term field monitoring, experimental ecology, molecular endocrinology, and controlled aquaculture studies, these works illustrate both the complexity and the applied relevance of fish reproductive systems.The study on yellowtail scad, Trachurus novaezelandiae by Stewart et al., provides a compelling example of how long-term datasets can inform sustainable exploitation. Drawing on 25 years of monitoring in south-eastern Australia, the authors characterize maturity schedules, spawning seasonality, and sex ratios in both natural populations and commercial catches. Sexual maturity occurs at relatively small sizes, with an extended spawning season from July to March and a peak in austral spring.Of particular interest is the consistent female-biased sex ratio in commercial landings, which may reflect sex-specific availability linked to reproductive behavior. Such findings emphasize that reproductive dynamics influence not only population productivity but also fisherydependent sampling and catch composition. As harvest pressure on small pelagic species increases, reproductive baseline data such as these become indispensable for estimating spawning stock biomass and maintaining sustainability classifications. This contribution reminds us that reproductive biology is not merely descriptive it is foundational for effective fisheries management, especially for species whose ecological roles amplify their importance within marine food webs.In aquaculture, reproductive biology intersects directly with production efficiency. The investigation of male-biased gonadal differentiation in hatchery-reared blackthroat seaperch Doederleinia berycoides by Tori et al., addresses a persistent bottleneck in seed production. While wild populations show no sex-ratio bias and no evidence of protandrous sex change, hatchery populations frequently exhibit male-skewed ratios, suggesting that artificial rearing environments influence sex differentiation.Histological analyses demonstrated that early morphological markers are insufficient for reliable pre-stocking sex identification. The authors therefore turned to RNA-seq and gene expression profiling, identifying sex-specific molecular markers such as dmrt1, amh, cyp11b1, foxl2a, and wnt-4a. Notably, the detection of foxl2a expression in female fin tissue opens the possibility of non-lethal sex identification, an important advance for hatchery management.This study underscores the increasing importance of molecular tools in applied reproductive biology. It also highlights how environmental conditions in artificial systems can disrupt natural developmental trajectories, reinforcing the need to understand endocrine and genetic regulation in aquaculture contexts.Reproductive output is not determined solely by maturity schedules; it is deeply influenced by energy allocation strategies. The experimental study on chub mackerel Scomber japonicus by Yoneda et al., provides rare empirical evidence for a mixed breeding strategy shaped by maternal nutritional history.Using stable isotope tracers and controlled feeding experiments, the authors demonstrate that chub mackerel rely predominantly on stored energy reserves (capital breeding), with limited reliance on concurrent feeding during spawning. Food restriction months prior to spawning significantly reduced somatic condition, egg production, and larval performance, including growth and starvation tolerance.These findings reveal strong maternal effects extending beyond egg production to larval quality and survival potential. In density-dependent systems where prey availability fluctuates, such reproductive plasticity can drive interannual variability in recruitment. The study therefore bridges individual physiology with population-level dynamics, providing a framework to interpret recent changes in stock productivity in light of maternal nutritional history.The final contribution also focuses on chub mackerel Scomber japonicus, by Il Baek et al., examining the reproductive cycle of cultured broodstock maintained in land-based tanks in Jeju Island, Korea. By monitoring fish under natural temperature and photoperiod regimes for 12 months, the study delivers essential data for optimizing broodstock conditioning and spawning reliability. Importantly, delayed spawning under controlled conditions is discussed in relation to chronic stress, confinement, altered environmental cues, and endocrine regulation. These observations highlight a recurring theme across aquaculture species: while environmental parameters may approximate natural cycles, subtle differences in stress load, diet, or sensory stimuli can significantly alter reproductive timing.Such insights reinforce the necessity of integrating physiological, environmental, and behavioral perspectives when designing broodstock management protocols. Reliable spawning in captivity is a prerequisite for closing life cycles in aquaculture-a goal that reduces dependence on wild seed and enhances production sustainability.Collectively, these studies demonstrate that reproductive biology operates across interconnected biological and production scales, each essential for the sustainability of commercially important marine fish species. At the population level, parameters such as size and age at maturity, spawning seasonality, and sex ratios provide the foundation for accurate stock assessment and reliable estimates of spawning stock biomass. Such knowledge is critical for maintaining sustainable harvest strategies, particularly in small pelagic species subject to increasing fishing pressure.At the developmental and molecular level, advances in understanding the genetic and endocrine regulation of sex differentiation offer practical solutions to hatchery bottlenecks. The identification of sex-specific molecular markers enables earlier and potentially non-lethal sex determination, improving broodstock selection and enhancing production efficiency in aquaculture systems where skewed sex ratios can compromise yield.Physiologically, reproductive output is tightly linked to energy allocation strategies and maternal nutritional history. Evidence that maternal condition influences egg production, larval growth, and starvation tolerance highlights the need to incorporate maternal effects into evaluations of recruitment variability and stock productivity.Finally, at the production scale, environmental control within aquaculture systems, encompassing temperature, photoperiod, diet, and stress management, directly influences endocrine regulation and spawning reliability. Together, these perspectives emphasize that reproductive biology forms the mechanistic bridge between environmental conditions, population resilience, and sustainable seafood production in a rapidly changing marine environment.