Introduction
European inland aquaculture needs to diversify production (Baekelandt et al., 2018). Pikeperch (Sander lucioperca) was chosen due to its high value, fast growth, and flesh quality as a prime candidate and embedded into freshwater inland aquaculture. Thanks to its qualities production of pikeperch in aquaculture is constantly increasing. In case of west Europe such as Belgium. Netherlands and France, the missing pond network is forcing the farmers to produce pikeperch in closed recirculating aquaculture systems (RAS). In Central and East Europe countries overall share of aquaculture production up to 80-88% (Vavrečka et al., 2019) originates from ponds. The existing pond infrastructure in the combination with new technological equipment offers the opportunity to increase the production capacity of the ponds. IPRs (In-Pond Raceways) provide better water quality, are easy to install with lower input investment to existing ponds and also provide better water circulation and aeration while using airlift as a powering medium. IPRs was so far used for pikeperch culture only in two published studies regarding broodstock management (Ljubobratović et al., 2019) and grow-out phase of juveniles (Nagy et al., 2022).
Material and methods
In this study juveniles of pikeperch were introduced into experimental RAS, IPRs and POND. Into each experimental group, in total 1500 juveniles were stocked. Fish were cultured in each system for 24weeks in monoculture (RAS and IPRs) and polyculture (POND) with cyprinid stocking. After the duration of the experiment pikeperch juveniles were harvested and data were collected. Production parameters concerning growth and feed utilization were calculated (only in RAS and IPRs) . To provide a comprehensive overview of pikeperch physiological state, blood and tissue sampling were carried out together with fin erosion grading. From collected samples of blood and tissue biochemical parameters of the blood were assessed together with somatic indexes.
Results and discussion
Fish from RAS displayed the highest growth FTL (Final Total Length), FBW (Final Body Weight), CF (Condition Factor) , SGR (Specific Growth Rate) and significantly lowest FCR (Food Conversion Ratio) compared to other groups. Physiological status of the fish regarding biochemical profile of plasma and somatic indexes was in the correlation with fast growth and efficient feed utilization . I ncreased hepatosomatic index in RAS based fish together with high levels of ammonia (NH3) in blood suggests increased metabolism rate. High feed intake also manifested on significantly increased fat deposits in RAS juveniles. I ncreased level of albumins may suggest beginning of RAS based fish liver malfunction. In according to
more frequent erosion of caudal fin was found in RAS based individuals. Group raised in IPRs achieved slower but satisfactory growth. FCR was found significantly higher in IPRs group. Until today no study covering feeding in IPRS is published therefore it represents the possibility of increase of culture efficiency via feeding management optimization. Biochemical prof ile of plasma uncovered significantly increased levels of glucose directly connected to a stressful harvest of otherwise unbothered fish in IPRs. Fish raised in IPRs displayed erosion on both pectoral fins probably because of presence of the fish in a more turbid environment on the bottom of the IPRs tanks. Pikeperch juveniles in POND group didn’t cope well with transition to their natural environment in pond polyculture with cyprinid fish. Pikeperch individuals in POND group displayed significantly lowest SR amongst all groups. Biochemical plasma profiling suggested starvation via increased levels of ALP (alanine aminotransferase) and non-existing fat reserves. POND raised juveniles also displayed significantly longest gut. Low survival rate was probably also caused by excessive algae bloom, oxygen deficiency and turbidity. In summary fish in RAS displayed most intensive growth and most successful feed utilization. IPRs was proven as an appt way of pikeperch juveniles production during vegetational season. Despite slower growth of the fish in IPRs reduced production cost per juvenile makes up for the difference .
Acknowledgements
The study was supported by the Ministry of Agriculture of the Czech Republic, project NAZV QK23020002 and Ministry of Education, Youth and Sports, project GAJU 0362024T.
References
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