Introduction
Freshwater Integrated Multi-Trophic Aquaculture (F-IMTA) represents a promising strategy to improve the environmental sustainability and economic resilience of traditional pond-based aquaculture. By co-culturing complementary trophic groups alongside a primary fed species, F-IMTA systems can intercept excess nutrients, reduce the risk of eutrophication, and diversify farm revenues. In Central and Eastern Europe, common carp (Cyprinus carpio) pond farming is a dominant aquaculture model with significant cultural and ecological value, yet it faces growing pressure from environmental regulation, climate-driven water stress, and market competition (Panicz et al. 2022). This work presents the development and demonstration of F-IMTA at the I��skie Centrum Rybactwa (ICR) farm in Maliniec, northwestern Poland, across two consecutive research frameworks. The F-IMTA concept was first piloted at ICR under the Horizon Europe SmartAqua4Future (SAFE) project, which applies circular-economy approaches to freshwater aquaculture waste streams (Nederlof et al. 2022, Eljasik et al. 2026). The SAFE pilot combined common carp with narrow-clawed crayfish (Pontastacus leptodactylus) and watercress (Nasturtium officinale) in dedicated ponds separate from the main production. In parallel, the project applied a circular economy approach in which carp sludge and straw bricks served as substrate for oyster mushroom production; the resulting spent mushroom substrate was then used to rear mealworms, with mealworm meal evaluated as a sustainable feed ingredient for carp. In parallel, FISHPLANT, a separate project co-funded by ZUT and ICR through the European Maritime and Fisheries Fund (2022–2023), established new low-input, multitrophic fish-and-plant production infrastructure at the same farm site. Building on these foundations, a full commercial-scale F-IMTA demonstration was implemented during the 2025 production season under the BLUEBOOST project (Sustainable Blue Economy Partnership, Grant No. SBEP2023-725), generating the first high-resolution empirical nutrient mass-balance dataset for carp-based F-IMTA under real operational conditions.
F-IMTA System Design and Deployment
The SAFE project established the initial F-IMTA pilot at ICR using dedicated smaller-scale ponds, demonstrating the feasibility of combining carp with narrow-clawed crayfish and watercress as extractive components. A distinctive circular economy feature of SAFE was the use of carp sludge and straw bricks as substrate for oyster mushroom cultivation; the resulting spent mushroom substrate was subsequently used to rear mealworms (Tenebrio molitor), with the produced mealworm meal evaluated as a sustainable feed ingredient for carp, closing the nutrient loop within the farm. The FISHPLANT project (2022–2023), co-funded by ZUT and ICR through the European Maritime and Fisheries Fund, further strengthened the farm's research infrastructure and resilience by establishing dedicated low-input multi-trophic fish and plant production facilities. Under BLUEBOOST, these combined foundations enabled a full commercial-scale F-IMTA demonstration during the 2025 production season. The F-IMTA integrated carp production in an 11 ha pond (pond no. 15) with a floating crayfish cage module (8.07 × 13.90 m, 15 individuals per cage) and a 50 m2 watercress production unit positioned in the concrete outflow channel downstream of the pond. Half of the watercress area was covered by a foil tunnel to assess the influence of microclimate on plant growth. Carbon (C), nitrogen (N), and phosphorus (P) flows were quantified using a site-specific mass-balance approach integrating elemental analysis of all system components with a thermal-unit growth model to simulate carp biomass dynamics throughout the full May–November production season.
Results and Discussion
The ICR demonstration confirmed the technical feasibility of the F-IMTA concept under commercial operating conditions, with all components functioning within the existing farm schedule and infrastructure. The 2025 mass-balance analysis showed that watercress harvested 19.0 kg C, 0.86 kg N, and 0.13 kg P, while crayfish contributed an additional 0.13 kg C, 0.04 kg N, and 0.01 kg P. The overall bioremediation potential of the extractive species relative to feed-derived carp emissions was 0.09% for C, 0.014% for N, and 0.058% for P. Although these values appear low in absolute terms, they reflect the open, flow-through character of semi-intensive pond systems, where the total nutrient pool is highly diluted. The key design principle, i.e. targeting outflow hotspots rather than the entire pond volume, is the critical functional distinction from closed-system IMTA. Additionally, straw bricks placed in the drainage channel sequestered 147.9 kg C, 2.86 kg N, and 0.44 kg P during the season, providing a complementary passive filtration mechanism. These results, derived from longitudinal, site-specific laboratory analyses rather than literature defaults, provide a high-resolution empirical basis for Life Cycle Assessment (LCA) within the BLUEBOOST project and establish a reproducible benchmark for future optimisation of nutrient recovery in temperate freshwater aquaculture.
Acknowledgment
Co-funded by the European Union. This work was supported by the BLUEBOOST project (Grant No. SBEP2023-725), funded by the Sustainable Blue Economy Partnership (SBEP), by the SAFE project (Grant No. 101084549), and by the FISHPLANT project (Grant No. 00003-6521.1-OR1600001/22).
Views and opinions expressed are, however, those of the author(s) only and do not necessarily reflect those of the European Union. Neither the European Union nor the granting authority can be held responsible for them.
References
Eljasik P., N��dzarek A., Sobczak M., Lisiecki S., Roy K., ��mietana P. & Panicz R. (2026) Evaluating nutrient removal efficiency of aquatic plants in pond aquaculture discharges. Aquaculture 615, 743645. https://doi.org/10.1016/j.aquaculture.2026.743645
Nederlof M.A.J., Verdegem M.C.J., Smaal A.C. & Jansen H.M. (2022) Nutrient retention efficiencies in integrated multi-trophic aquaculture. Reviews in Aquaculture 14(3), 1194–1212. https://doi.org/10.1111/raq.12645
Panicz R., Ca��ka B., Cubillo A., Ferreira J.G., Guilder J., Kay S. et al. (2022) Impact of climate-driven temperature increase on inland aquaculture: Application to land-based production of common carp (Cyprinus carpio L.). Transboundary and Emerging Diseases 69(5), e2341–e2350. https://doi.org/10.1111/tbed.14577