Intensive aquaculture employs bi- or polycultural methods inspired by pond aquaculture, where mixed fish stocks increase productivity and profitability (Turnšek et al., 2019). Polyculture, a technique according to Dalsgaard et al. (2013), stands as a beacon in aquaculture, ingeniously harnessing the potential of multiple fish species to optimize productivity, resource utilization, and ecological sustainability.
Juvenile pikeperch [n=1224; total length (TL) = 131.5 ± 6.9 mm and body weight (BW) = 18.2 ± 2.7 g] and sturgeons [n=576; total length (TL) = 168.1 ± 12.5 mm and body weight (BW) = 18.2 ± 3.6 g] were stocked in five groups (with triplicates): pikeperch (P100) and Russian sturgeon (P0) monocultures, and three types of bicultures with different stocking ratios of pikeperch and sturgeon (P90, P80 and P70). The distribution of fish species varied across different groups. In group P100, all 120 fish were pikeperch. Group P90 consisted of 108 pikeperch and 12 sturgeons. Group P80 had a mix of 96 pikeperch and 24 sturgeons. In group P70, there were 84 pikeperch and 36 sturgeons. Lastly, group P0 was entirely stocked with 120 sturgeons. The Daily feed ratio was set at 1% of the total biomass of fish per tank. After 28 days, each tank was weighed and the current daily feed intake for each group was recorded. Production parameters [TL, somatic length (SL), Fulton’s condition coefficient (FC), specific growth rate (SGR), thermal growth coefficient (TGC), feed conversion ratio (FCR), specific heterogeneity rate (SHR), survival rate (SR)] and fin condition among tested groups were assessed at the beginning and end of the experiment. The pectoral, ventral, dorsal, caudal, and anal fins, and the level of fin damage rate were determined according to Policar et al. (2016). Blood samples were collected from 6 anesthetized fish per group at the beginning and end of the feeding trial for biochemical analysis, including plasma levels of total protein (TP), albumin (ALB), globulin (GLB), amylase (AMYL), lipase (LIPA), total cholesterol (TCHOL), glucose (GLU), ammonia (NH3), and triglyceride (TAG).
Following the 84-day trial, there were no significant differences in fish biometric parameters (TL, SL, BW) among all tested groups, regardless of species (pikeperch: F(3,360) = 1.0; sturgeon: F(3,360) = 1.0; p > 0.05; SL: pikeperch: F(3,360) = 3.7; sturgeon: F(3,360) = 0.2; p > 0.05; BW: pikeperch: F(3,360) = 1.5; sturgeon: F(3,360) = 0.2; p > 0.05). Pikeperch was the species most affected by biculture compared to sturgeon at the end of the experiment. The final TL, SL, and BW differed depending on the treatments (ANOVA: F(3,596) = 28.1, p < 0.01 for TL; F(3,596) = 29.5, p < 0.01 for SL; F(3,596) = 36.8, p < 0.01 for BW). For all these parameters, the values for fish in P100 were lower than those in biculture Groups P90, P80, and P70 (Figure 1).
Pikeperch’s SGR was lowest in Groups P100 and P90 and highest in Groups P80 and P70. No significant differences were observed in the SGR of Russian sturgeon among the groups. Pikeperch in Groups P80 and P70 had the highest TGC, while the lowest was in Groups P100 and P90. The highest TGC for Russian sturgeon was in the monoculture Group P0. Pikeperch survival rate ranged from 96.0% to 98.6% across all groups, with no mortality in sturgeon groups. Feed conversion ratio (FCR) was highest for pikeperch in Group P100 and for sturgeon in Group P90. Significant differences in hepatosomatic index (HSI) and Fulton’s condition index (FSI) were found only within pikeperch groups. No significant differences were found in somatic indices for both species. Caudal fin erosion was most pronounced in pikeperch from the P100 group.
Acknowledgements
This study was supported by the Ministry of Agriculture of the Czech Republic (project NAZV QK23020002) and by Ministry of Education, Youth and Sports of the Czech Republic – CENAKVA project (LM2018099).
References
Dalsgaard, J., Lund, I., Thorarinsdottir, R., Drengstig, A., Arvonen, K., Pedersen, P.B., 2013. Farming different species in RAS in Nordic countries: Current status and future perspectives. Aquacultural Engineering 53, 2–13. https://doi.org/10.1016/j.aquaeng.2012.11.008
Turnšek, M., Morgenstern, R., Schröter, I., Mergenthaler, M., Hüttel, S., Leyer, M., 2019. Commercial Aquaponics: A Long Road Ahead, in: Goddek, S., Joyce, A., Kotzen, B., Burnell, G.M. (Eds.), Aquaponics Food Production Systems. Springer, Cham, pp. 453–485. https://doi.org/10.1007/978-3-030-15943-6_18