Introduction
Despite the significant dependence on the expression of natural behaviour in pikeperch aquaculture production, the knowledge of its reproduction biology remains limited (Lappalainen, Dorner, and Wysujack 2003; Malinovskyi et al. 2023; Olin et al. 2018). Recent reports show that the reproductive performance of pikeperch males during natural spawning season could vary significantly, and as a result affecting females spawning decisions and the overall efficacy of reproduction, suggesting species sensitivity to shifts in reproduction behaviour (Malinovskyi et al. 2023; Teletchea et al. 2009). The potential impact of rearing history on spawning behaviour can have significant implications for the natural reproductive capacity of broodstock, raising concerns about the suitability of intensively-cultured fish for restocking and replenishment programs. Likewise, there are yet commercial farms using the hormone-free nest spawning technique that are intrigued by the potential of reproductive behaviour modulation.
Several studies found modified reproductive biology of intensively- vs extensively reared breeders (Khendek et al. 2018; Ljubobratović et al. 2017, 2023), which might likewise imply modification of its reproductive capability in terms of practicing natural spawning. Thus, the study aims to investigate the potential influence of broodstock rearing history (pond- vs. intensively-reared) on their ability to express natural reproductive traits. The study seeks to understand whether it affects spawning decisions, reproductive effectiveness, and overall reproductive capacity in pikeperch broodstock during natural spawning on the nest.
Material and methods
To accomplish this, the study will use four sets of pikeperch broodstock for natural spawning on the nest, comprising fish with different rearing histories : (1) both sexes pond-cultured; (2) pond-cultured males and intensively -cultured females; (3) intensively -cultured males and pond-cultured females; (4) both sexes are intensively -cultured. The fish in each set were provided with artificial spawning nests and no hormonal induction of spawning. This approach allowed assessment of the capability of pikeperch broodstock to exhibit natural spawning behaviour, providing valuable insights into the potential influence of the rearing history on their reproductive performance. Each nest was photographed, and the image was analysed with the open-source image processor ImageJ. The analysis included the determination of the cleaned area and area of egg distribution relative to the total nest area.
Results and discussion
Results: Preliminary findings indicate a significant difference in the spawning success rate between pond-cultured and intensively cultured pikeperch broodstock. Pond-cultured fish demonstrated significantly better nest-cleaning efforts and more even distribution of eggs on the nest. Additionally, there was a considerable difference in the biochemical profile of blood plasma, particularly cortisol and glucose levels, which suggests a stress response in intensively cultured fish.
Discussion: The results suggest that the rearing history of pikeperch broodstock significantly affects their natural reproductive behaviour and spawning success. Pond-cultured fish not only performed better in terms of nest preparation and egg distribution but also exhibited lower stress levels, as indicated by their biochemical profiles. These findings highlight the importance of rearing conditions in aquaculture practices and their potential impact on the reproductive performance of broodstock. The observed stress response in intensively cultured fish raises concerns about their suitability for natural spawning and restocking programs. Further research is needed to explore the mechanisms underlying these differences and to develop strategies to improve the reproductive performance of intensively cultured broodstock.
Acknowledgements
The study was supported by the Aquaexcel 3.0 TNA project – 26814 NATURESANDER.
References
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