Diversifying Central and Eastern Europe pond production with hybrid striped bass Morone saxatilis x Morone chrysops monoculture vs. cage polyculture

A 13-week experiment was conducted to investigate the effects of two different production systems (pond monoculture vs. cage polyculture) and unit sizes (small, large) on the production and slaughter characteristics of hybrid striped bass (Morone saxatilis x Morone chrysops, HSB), as well as on water quality. The HSB were stocked in the same density according to the pond size (850 kg ha−1), making in total of 27 kg and 59 kg in the small and large ponds, respectively. In the cage group (HSB density 2.5 kg m−3), common carp (Cyprinus carpio) were stocked outside of the cage with a stocking density of 500 kg ha−1. The technology significantly influenced the water quality parameters due to the macrophyte vegetation in the monoculture, while the only parameters affected by unit size were ammonium, nitrogen, and nitrogen/phosphorus ratio. Better HSB culture performance was seen in the monoculture pond group. The net yield of HSB was significantly higher both in the monoculture groups and in the small ponds, but including carp the combined polyculture produced 0.5 t ha⁻¹ more total biomass. The fillet ratio was higher in the monoculture, while the unit size affected the carcass and viscerosomatic index. In summary, hybrid striped bass achieved higher growth and slaughter yield in monoculture ponds, while the carp component in polyculture did not improve water quality or act as an effective biofilter. Nevertheless, the cage–pond polyculture can be economically advantageous, as it improves the overall feed conversion efficiency by converting supplementary feed into a higher combined yield of marketable fish (bass + carp) per unit of feed cost.