Introduction
In recirculating aquaculture systems (RAS), carbon dioxide (CO₂) accumulates due to respiration and microbial activity, potentially impairing fish growth performance. Pikeperch (Sander lucioperca) is a promising candidate for intensive aquaculture in Europe (Müller-Belecke and Zienert, 2008; Overton et al., 2015; Policar et al., 2019), yet limited information is available regarding its tolerance to elevated CO₂ levels (Skov, 2019). This study aimed to evaluate the effects of three dissolved CO₂ concentrations (0, 15, and 30 mg/L) on the growth, feed efficiency, and physiological condition of juvenile pikeperch over a rearing period. Understanding CO₂ related responses is essential to optimize water quality management and welfare in intensive RAS.
Materials and Methods
Juvenile pikeperch (initial total length ~254 mm, body weight ~117 g) were randomly assigned to one of three CO₂ treatments: Low (0 mg/L), Medium (15 mg/L), and High (30 mg/L). Each treatment was replicated in triplicate tanks (50 fish per tank) connected to a shared RAS with controlled temperature, oxygen, and photoperiod. Fish were reared for 112 days and fed a commercial diet to apparent satiation by belt feeders. Key performance parameters, including total length (TL), standard length (SL), body weight (BW), and Fulton’s condition factor (K). Fish were measured at the beginning and end of the trial. Feed conversion ratio (FCR), specific growth rate (SGR), thermal growth coefficient (TGC), and survival rate (S) were calculated. Additionally, organosomatic indices (HSI, FSI, GSI, KSI) were determined at the end of the experiment. Fin erosion among tested groups was assessed at the beginning and end of the experiment. Variation in body weight was assessed using coefficient of variation (CVBW). Differences between treatments were analyzed by one-way ANOVA with Tukey’s post-hoc test (α = 0.05). The assessment of the pectoral, ventral, dorsal, caudal, and anal fins, along with the rate of fin erosion, was conducted based on the methodology described by Policar et al. (2016).
Results
Initial biometric data showed no significant differences among treatment groups (P > 0.05). At the end of the trial, fish reared under high CO₂ (30 mg/L) had significantly lower TL, SL, BW, and K compared to the low CO₂ group (P < 0.05). Final BW was highest in the low CO₂ group (297.34 ± 69.60 g), compared to medium (250.02 ± 69.62 g) and high (232.93 ± 60.81 g) CO₂. Feed efficiency was negatively affected at higher CO₂ concentrations, with FCR increasing from 1.09 (low CO₂) to 1.82 (high CO₂). SGR and TGC decreased with increasing CO₂, though differences were marginally non-significant (P = 0.063 and P = 0.066, respectively). No significant differences were observed in survival, organosomatic indices, or CVBW. No differences in fin erosion were observed between the tested groups.
Discussion
Elevated CO₂ concentrations in RAS significantly reduced the growth and condition of pikeperch, likely due to increased metabolic costs and reduced feed efficiency. These findings suggest that CO₂ concentrations above 15 mg/L may compromise fish performance, despite not affecting survival or physiological indices. Maintaining lower CO₂ levels appears beneficial for maximizing growth and feed efficiency in intensive pikeperch culture. The study highlights the need for CO₂ control in RAS design and operation to ensure optimal fish welfare and production outcomes.
Acknowledgements
This research was funded by the Ministry of Agriculture of the Czech Republic (project NAZV QL25020009) and the Ministry of Education, Youth and Sports of the Czech Republic through the CENAKVA project (LM2023038) and project supported by the Grant Agency of University of South Bohemia (143/2025/T). Additionally, part of this work was conducted with the assistance of the VVI CENAKVA Research Infrastructure (ID 90238, MEYS CR, 2023–2026).
References
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