Introduction
Reliable control of reproduction is essential for efficient broodstock management and reliable juvenile production in intensive aquaculture (Zohar and Mylonas, 2001; Mylonas et al., 2010). In many emerging aquaculture species, reproductive dysfunction under captive conditions remains a major bottleneck limiting species diversification and commercial production (Migaud et al., 2013). Impaired ovulation, reduced spermiation and poor synchronization of gamete availability frequently compromise hatchery performance and juvenile output.
Hormonal induction using gonadotropin-releasing hormone analogues (GnRHa) is commonly employed to stimulate final oocyte maturation, ovulation and spermiation (Mylonas et al., 2010). However, conventional hormonal treatments are often limited by rapid peptide degradation and short endocrine stimulation, requiring repeated broodstock handling and increasing stress-related risks (Carnevali et al., 2006).
Poly(lactic-co-glycolic acid) (PLGA) is a biodegradable and biocompatible polymer widely used in pharmaceutical sustained-release formulations (Makadia and Siegel, 2011). Encapsulation of GnRHa into biodegradable microparticles enables controlled hormone release over several days and may prolong endocrine stimulation during critical phases of gamete maturation (Matejkova and Podhorec, 2019; Knowles et al., 2022).
The present contribution evaluates the application of biodegradable microparticles for reproductive management in several fish species, with particular emphasis on pikeperch (Sander lucioperca), a high-value species of increasing importance in European intensive aquaculture.
Results and Discussion
This contribution investigates biodegradable microparticles as a controlled hormone delivery platform for reproductive management in emerging aquaculture species, with particular emphasis on pikeperch (Sander lucioperca), for which comprehensive data are available for both sexes.
In female pikeperch, microparticles containing low doses of alarelin significantly improved ovulation success and reproductive performance compared with conventional hormonal treatment. Sustained hormone-release enhanced spawning induction while reducing the total hormone dose required.
In male pikeperch, microencapsulation of alarelin prolonged endocrine stimulation and maintained sperm motility characteristics under hatchery conditions, indicating the potential to improve synchronization and extend the functional fertilisation window.
The delivery system was designed to protect peptide hormones from rapid degradation and maintain effective hormone availability during critical phases of gamete maturation. This approach addresses one of the principal limitations of conventional gonadotropin-releasing hormone analogue treatments, namely the short duration of hormonal stimulation and the need for repeated broodstock handling.
In addition to pikeperch, this technology was successfully evaluated in peled (Coregonus peled), northern pike (Esox lucius), sterlet (Acipenser ruthenus) and bala shark (Balantiocheilos melanopterus). Positive reproductive responses across teleosts and sturgeons indicate broad applicability in species with diverse reproductive strategies and production requirements.
From a practical perspective, controlled hormone delivery may improve synchronization of ovulation and spermiation, reduce handling stress and increase the reliability of juvenile production. By improving reproductive control under captive conditions, biodegradable microparticles may support species diversification and facilitate the introduction of new fish species into intensive aquaculture systems.
Conclusion
Biodegradable microparticles represent a versatile platform for the controlled delivery of reproductive hormones in fish. Results obtained in pikeperch (Sander lucioperca) and additional fish species demonstrate that sustained-release formulations can improve reproductive synchronization, reduce broodstock handling and enhance the reliability of juvenile production under captive conditions. The integration of pharmaceutical sustained-release systems into broodstock management offers a promising approach for overcoming reproductive bottlenecks in emerging aquaculture species. By improving reproductive control and hatchery reliability, biodegradable microparticles may support species diversification and facilitate the introduction of new fish species into intensive aquaculture systems.
References
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Knowles, J., Vyslou��il, J., Policar, T. et al. (2022). Spawning Performance and Sex Steroid Levels in Female Pikeperch Sander lucioperca Treated with Poly(lactic-co-glycolic acid) Microparticles. Animals 12, 208.