Effect of common carp group, mass yield and supplemental feeding on basic water quality parameters under semi-intensive pond management in Central Europe: Implications for selective breeding under near-natural conditions

Aquaculture in Central Europe, particularly in Czechia, is mainly focused on common carp farmed in near-natural fishpond ecosystems. Therefore, any attempt to intensify the carp farming, including selective breeding, raises concerns about water quality and environmental impacts. Therefore, the aim of this study was to evaluate the effect of increased common carp production and different supplemental feeds (grain and carp plant-based pellets) on basic water quality parameters in fishponds. Two common carp stocks were monitored for this purpose. The crossbreed M2 x AMC represented a group with higher performance potential, while the M2 breed represented a stock with average performance. The common carp stocks were reared in 58 fishponds under common practice in three age categories, and 32 of them passed all the filtration criteria. The total mass of carp in the fishponds ranged from 140 kg*ha−1 to 1579 kg*ha−1. Fishponds stocked with the M2 x AMC group had a 51 % higher predicted total carp mass yield using generalized linear models. When assessing i) water quality parameters in fishponds stocked with common carp groups of different production parameters, ii) Pearson correlations between production and water quality parameters, and within water quality parameters, and iii) principal component analysis of production and water quality parameters, it can be estimated that doubling the carp production in fishponds should not significantly affect the self-cleaning function of fishpond ecosystems. No differences in water quality parameters were found for fishponds fed with either wheat grain or plant-based carp pellets. However, the water quality parameters deteriorated with increasing relative feed conversion ratio. •Genetic improvement of carp performance had no effect on fishpond water quality.•Negligible effect of carp production on fishpond water quality was found.•Wheat and plant-based carp pellets had comparable effect on fishpond water quality.•Water quality in fishponds depended on the trophic state of their tributaries.