Abstract
Recirculating aquaculture systems (RASs) are seen as a promising technology to address the societal and environmental challenges of aquaculture. However, this technology is mainly used in intensive monoculture and little knowledge is available in polyculture approaches. In this study, we studied survival, growth performance, and behaviour of juvenile pikeperch Sander lucioperca reared in RAS either in monoculture or in polyculture (associated with sterlet Acipenser ruthenus or tench Tinca tinca or both sterlet and tench). After 30 days, the survival rate was 100 % for both monoculture and polyculture reared pikeperch. The mean final weights and the biomass gain of pikeperch were significantly lower for pikeperch alone (respectively 75.7 ± 2.7 g and 25.2 %) or with sterlet (respectively 81.0 ± 3.2 g and 38.3 %) than in combination with tench (respectively 85.7 ± 8.1 g and 50.1 %) or with sterlet and tench (respectively 90.3 ± 16.4 g and 51.5 %). Behavioural changes were also detected depending on the fish combination: there are fewer interactions between individuals of pikeperch when reared alone (0.34 ± 0.10) or in polyculture with sterlet (0.40 ± 0.02) in comparison to the other polyculture conditions (with tench [0.80 ± 0.20], or the two other species [0.70 ± 0.15]). The group structure also differed with a lower cohesion and homogeneity of the pikeperch group when they were reared in monoculture compared to polyculture modalities. No aggressive interaction was detected between pikeperch regardless of rearing modalities. In conclusion, due to positive effects on growth parameters and few behavioural changes in pikeperch, this study highlights that RAS polyculture is a relevant alternative production strategy for pikeperch compared to monoculture.
Highlights
Aquaculture has been experiencing exponential development over the past decades to ensure human food demands, while capture fishery has remained stagnant (FAO, 2018)
Our results show that the Recirculating aquaculture systems (RASs) polyculture of the pikeperch positively affects juvenile fish rearing performance without affecting deeply their behaviour
Even though feed quantities were lower when pikeperch juveniles were associated with the other species due to the lower biomass of these species, pikeperch benefited from the totality of the feed during its presence in the water column. This meant that there could have been less competition between pikeperch as they had larger amounts of food per individual by taking the feed before the other two species. This hypothesis was supported by the results from the behavioural analysis, which revealed lower cohesion and homogeneity of the pikeperch group when they were reared alone compared to polyculture modalities
Summary
Aquaculture has been experiencing exponential development over the past decades to ensure human food demands, while capture fishery has remained stagnant (FAO, 2018). RASs offer the following advantages: reduction in the amount of water required to produce aquatic food, minimal space requirements for aquatic species production, higher control on rearing conditions compared to other systems, limitation of environmental deleterious consequences of aquatic food production by facilitating the treatment of effluents and minimising the risk of escape of domesticated individuals to the wild (FAO, 2018). To fill this gap, we conducted here the first multi-trait assessment of the consequences of RAS polyculture by comparing survival rates, growth performance and behaviour of the pikeperch (Sander lucioperca), a freshwater carnivorous species, in monoculture or in polyculture with two other species, the sterlet (Acipenser ruthenus) and the tench (Tinca tinca). The aim of this study was to compare survival rates and growth and behaviour of pikeperch reared alone and with other fish species
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