A novel multitrophic concept for the cultivation of fish and duckweed: A technical note

The authors report on the design and operation of an advanced, innovative and environmentally friendly freshwater integrated multitrophic aquaculture (IMTA) system. The novel system facilitates fish production while controlling water quality using duckweed treatment units. The basic design consists of ponds for farming of Eurasian perch and rainbow trout, treatment areas for the culture of duckweed (Lemna minor and Lemna gibba), as well as connecting channels. An important aspect of the farm is its close association with a renewable energy source. The system is driven by electric energy produced by a wind turbine and uses unused cutaway peatland left after peat harvesting was completed. Water analysis shows that a combination of fish and duckweed farming can maintain a favourable water quality. Moreover, production of both fish and plant biomass are substantial, with fish production of 0.49 ± 0.20 kg fish.m⁻².year⁻¹, water use efficiency of 1.21 ± 0.42 kg fish.m⁻³ year⁻¹ and electricity use of 16.1 ± 11.2 kWh.kg⁻¹.year⁻¹. Additionally, the system produced in excess of 30 tonne (dry weight) protein-rich duckweed biomass per year, which is a suitable feedstock for a variety of farmed animals.