Introduction
The rapid expansion of salmon aquaculture is increasing demand for sustainable aquafeeds and placing pressure on conventional feed resources (Alm��s et al., 2023; Milj��stiftelsen Bellona, 2022; OECD/FAO, 2025). Gammarids and polychaetes offer promising circular feed solutions by converting underutilized organic side streams into nutrientrich biomass (Alberts-Hubatsch et al., 2019; Anglade et al., 2023; Ribes-Navarro et al., 2022; Wang et al., 2019). Yet, knowledge on both their biological performance and environmental impacts remains limited for these novel ingredients to advance from concept to application, due to the absence of industrialscale production of these species in Scandinavia.
Materials and methods
This study evaluated grass and featherbased diets for gammarids (Gammarus duebeni and Gammarus oceanicus) and polychaetes (Hediste diversicolor), assessing growth, survival, and biochemical composition in smallscale feeding trials. An accompanying life cycle assessment (LCA) compared baseline and alternative feed scenarios for gammarid and polychaetederived protein meals (1���kg protein), as well as other novel protein sources.
Results and discussion
Both species groups were able to utilize grass��� and feather���based diets, but growth rates were limited (1.23���±���0.39���%���d-1 in polychaetes and ���0.38���±���0.10 to 0.50���±���0.24���%���d-1 in gammarids), likely due to limited feed composition, low digestibility and nutrient availability. However, in gammarids, a more digestible grass–sediment mixture performed similarly to the control diet, suggesting that further diet optimization could improve outcomes, while pure grass and feathers demonstrated basic survival potential. Amino acid profiles remained stable in the organisms, and polychaetes retained essential fatty acids (EPA and ARA), indicating potential for trophic upgrading. From an LCA perspective, reduced growth in the alternative feed scenarios compared to baseline scenarios increased rearing times and thus environmental impacts across all categories.
Overall, the results highlight both the potential and current constraints of using circular substrates in lowtrophic species production. Further improvements in substrate processing, diet formulation, and system optimization will be necessary to enhance productivity and reduce environmental impacts, supporting the future role of gammarids and polychaetes in sustainable aquaculture feed systems.
Acknowledgements
This work was funded by the BlueGreenFeed project (grant no. 339164), the Norwegian Center for Plankton Technology, and internal SINTEF Ocean funding, and the authors thank colleagues for technical support and biochemical analyses.
References
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