Introduction
Restocking success depends not only on the number and size of released fish, but also on their functional readiness to survive under natural conditions (Holubov�� et al., 2025). Pikeperch (Sander lucioperca) juveniles produced in intensive aquaculture systems may differ from pond-reared fish in swimming behaviour, spatial use, and response to environmental stimuli (Moln��r et al., 2018; Turesson et al., 2006). These differences can reduce their ability to adapt after release. Therefore, pre-release adaptation protocols may represent an important tool to restore natural swimming behaviour and improve the performance of cultured pikeperch before restocking.
Materials and Methods
Pikeperch (Sander lucioperca) juveniles with an average body weight of approximately 30 g were used in the study. Fish were stocked into two earthen ponds, each with an area of 50 m2, at a density of 5,000 individuals per pond. The pre-release adaptation period lasted two weeks. Two adaptation treatments were tested. In the first pond, pikeperch were exposed only to the presence of prey fish. In the second pond, pikeperch were exposed to a combination of prey and predator stimuli. The prey community consisted of native white fish, including roach (Rutilus rutilus), while predator stimuli were represented by European catfish (Silurus glanis), northern pike (Esox lucius), and European perch (Perca fluviatilis), with one individual of each predator species present. Swimming characteristics were assessed before and after the two-week adaptation period under controlled experimental conditions. Fish movement was recorded and analysed using computer-assisted image analysis based on EthoVision software. This approach enabled comparison of swimming performance and behavioural characteristics before and after adaptation, and allowed evaluation of the effects of prey-only exposure versus combined predator–prey exposure on swimming behaviour. The experimental design made it possible to separate the influence of prey presence from the additional effect of predator presence.
Results and Discussion
Swimming behaviour of pikeperch juveniles changed significantly after the two-week pre-release adaptation period. Significant differences were observed in total swimming distance, shelter use, maximum swimming speed, and overall duration of swimming activity. Comparison of the prey-only and combined predator–prey treatments allowed us to distinguish the effect of prey presence from the additional influence of predator exposure. These changes suggest that pre-release adaptation modified locomotor activity, risk-related behaviour, and swimming capacity, indicating improved behavioural readiness of pikeperch before restocking.
Acknowledgment
This work / Part of the work was carried out with the support of VVI CENAKVA Research Infrastructure (ID 90238, MEYS CR, 2023–2026).
References
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