Effects of elevated carbon dioxide on growth performance and physiology of juvenile RAS-based Eurasian perch (Perca fluviatilis)

The present 105-day experiment studied the influence of exposure to carbon dioxide (CO2) in its dissolved form on the growth performance, somatic condition, blood plasma biochemistry, and fin integrity of Eurasian perch (Perca fluviatilis) juveniles reared in recirculating aquaculture systems (RAS). Eurasian perch juveniles (mean initial body weight of 117.7 ± 28.2 g) were divided into three CO2 groups in triplicate: Low (5 mg L-1, control), Medium (15 mg L-1), and High (30 mg L-1). The exposure to dissolved CO2 had a significant effect on total length, whereby the juveniles exposed to Low CO2 achieved significantly greater length as compared to Medium and High treatments (p = 0.009). Fulton’s condition factor (K) was significantly higher in Medium (2.35 ± 0.32) and High (2.34 ± 0.22) groups in comparison with the Low group (2.11 ± 0.24; p ≤ 0.001). Mean final body weight, standard length, specific growth rate (SGR), thermal growth coefficient (TGC), feed conversion ratio (FCR), and survival rate (as high as 99.33%) were not significantly different among the treatments (p > 0.05). Analysis of the somatic indices showed the trade-off between gonadosomatic index (GSI) and kidney/fat somatic indices, while no significant differences in blood plasma biochemical parameters were found (p > 0.05). The fin condition was very high, with an intact fin percentage ranging from 84% to 100%. Results indicate that chronic exposure to dissolved CO2 concentrations up to 30 mg L-1 does not compromise the welfare or production performance of juvenile Eurasian perch in RAS but may induce subtle physiological adjustments associated with altered energy partitioning and somatic development, reflected in increased condition factors and shifts among somatic indices.