Pikeperch is successfully used for the diversification of inland aquaculture due to its high-quality flesh, fast growth, and overall market profitability (Overton et al., 2015). Fully grown and marketable sized pikeperch is highly demanded by gastronomy industry and angling community . During the last decade this species was subjected to an intense scientific study in both Central and Western Europe. To establish pikeperch as a permanent part of European inland intensive aquaculture, the formulation of new feed is necessary to adequately address the specific nutritional needs of pikeperch. This issue was not yet solved. Also, the characteristics of the pellets itself, whether they float on the surface or sink to the bottom, may influence the growing rate and nutrient utilization of cultured and fed juvenile s. The present study is focused to determine the influence of the different pellets characteristics on the efficiency of pikeperch intensive production in RAS (Recirculating Aquaculture System) during grow out phase .
2. Material and methods
Experimental fish were stocked into 8 experimental tanks (1.5 m³ each) in one production RAS of Faculty of Fisheries and Protection of the Waters in Vodňany, Czech Republic. Juveniles in number of 8000 individuals (1000 juveniles per tank, mean IBW (Initial Body Weight) 21.38 ± 7.32 g, biomass of 13.42 kg. m- ³, were cultured ) for 112 days with control period of 28 days. After 14 days of adaptation experimental fish under new conditions, the experiment was started. Fish were fed during 16 hours per day using two commercial dry feed diets set at DFR (Daily Feeding Ratio) 1.2 % of fish biomass. The first group was fed with floating pellets Skretting Europa 15F (3.5 and 5mm). The s econd group was fed with sinking pellets Biomar Effico Sigma (3 and 4.5mm) Both types of pellets contain the same level of protein (55%) and of fat (16%). At the beginnin g and the end of experiment , 50 randomly selected experimental fish from each tank were measured . These fish were anesthetized in solution of clove oil (0. 04 ml.l-1). From this data following production markers were determined - IBW= Initial Body Weight; FBW= Final Body Weight, WG= Weight Gain, SGR= Specific Growth Ratio, TL= Total Length; FCR= Food Conversion Ration, CF= Condition Factor. Also, the growth heterogenity was assessed.
3. Results and discussion
An achieved final body weight of 80 g was observed in the more rapidly growing group fed by sinking feed , compared to 72 g in the g roup fed by floating feed . Group fed by sinking feed also exhibited significantly higher WG and TL indicating higher growth of fish fed by sinking feed. Higher feed utilization was found in group fed by sinking feed as well as evidenced by lower FCR of 0. 88 g.g-1 and a higher SGR of 1.24 %.d-1 compared to group fed by floating pellets which managed to reach FCR 0,93 g.g-1 and SGR
1.13 %.d-1. Both groups exhibited no statistical difference in survival rate (92. 13 and
94. 45 %). These results would suggest that sinking feed is a preferable choice. However, there were different results in growth heterogenity and C ondition Factor. Group fed by floating pellets reached statistically higher CF (1.16) compared to the other group (1. 09) probably because of increased physiological exercise resulting from periodical surfacing for floating pellets. Additionally, group fed by floating pellets showed lower growth heterogenity with fewer cases of cannibalistic and growth deprived individuals.
The study was supported by the Ministry of Agriculture of the Czech Republic, project NAZV QK23020002.
Overton, J. L., Toner, D., Policar, T., Kucharczyk , D., Chapter 35: Commercial Production: Factors for Success and Limitations in European Percid Fish Culture. In P. Kestemont , K. Dabrowski & R. C. Summerfelt (2015) (Eds.), Biology and culture of percid fishes (pp. 881–891). Dordrecht: Springer Netherlands. https://doi.org/10.1007/978-94-017-7227- 3_32