Introduction
Despite the high diversity of marine food fish, aquaculture is limited to relatively few species. Many marine species remain dependent on wild capture. Securing long-term supply therefore requires the successful establishment of new aquaculture species. Atlantic cod (Gadus morhua) and Atlantic halibut (Hippoglossus hippoglossus) are promising species for large-scale production. In contrast to Atlantic salmon (Salmo salar), cod and halibut still face biology- and nutrition-driven production challenges that limit predictable growth and quality, requiring adaptive feed development and close producer-farmer collaboration.
Challenges, materials, and methods
In cod, nutritional imbalances are associated with skeletal deformities, liver alterations, and intestinal abnormalities, particularly during early development and under intensive rearing conditions (Pedro et al., 2025). In halibut, impaired eye migration, ambicoloration, and skin wounds are major bottlenecks, with diet composition strongly influencing development outcomes (S��le et al., 2003; Hamre et al., 2007).
To address these challenges, feed development was conducted through a stepwise, trial-based collaboration between Aller Aqua and the farmers Havland and Sterling Halibut. Diets were refined to reflect species-specific nutritional sensitivities, improving performance, health, and sustainability.
Cod feed development followed a consecutive research approach. A baseline trial in 2022 at Aller Aqua Research evaluated nutrient requirements and pellet quality under controlled conditions. This was followed by a trial series in 2025 under recirculating aquaculture system (RAS) conditions, assessing dietary effects on water quality, growth, and skeletal deformities, with feed formulations adjusted based on biological responses. In 2026, a flow-through trial evaluates feed performance across production systems and the inclusion of alternative raw materials, with growth, deformities, and gut health monitored through regular sampling.
Halibut feed development applied a similar stepwise approach, focusing on protein source suitability. Following earlier indications of limited tolerance for plant ingredients, a land-based by-product protein was tested in 2023. A second alternative protein was added in 2024 to increase fishmeal replacement, and higher inclusion levels of the by-product were evaluated in 2025. Growth performance, health indicators, and sustainability metrics were assessed at regular sampling intervals.
Results
Cod feed development under RAS conditions established a functional baseline feed for land-based production, supporting stable performance and firmer feces that contributed to improved water quality. Skeletal deformities, including neck cracks, were observed but were assessed to be within the normal range for cod during grow-out phase. There is no clear evidence that deformities occur more frequently under RAS compared with other production technologies. The nutritional and physiological causes of neck cracks remain unclear and are therefore addressed as a general challenge for cod farming. An ongoing flow-through trial provides complementary data on feed performance and health parameters, across land-based systems and on the use of alternative raw materials.
Halibut feeding trials demonstrated strong potential for land-based protein sources into grower diets. Inclusion of a land-based by-product in 2023 resulted in similar growth performance between both diets. A combination of the by-product and another land-based protein source in 2024 resulted in good growth performance and 33% less wound prevalence in the test diet. Increasing the inclusion of the by-product from 2024 to 2025 resulted in 15.57% lower FCR in the test diet compared to control diet. The test diet consistently reduced the prevalence of wounds, with 40.58% less wound prevalence in the test diet compared to the control diet in 2025. The latest results indicate an association between eye migration, ambicoloration, and growth performance. The proportion of fully ambicolorated fish was 40% higher among individuals with incorrect eye migration compared to fully ambicolorated fish with correct eye migration. In addition, average body weight was 11.45% lower in fish with incorrect eye migration compared to fish with correct eye migration. Improved feed sustainability was reflected by a 27.52% reduction in FIFO through inclusion of the tested novel ingredients from 2025, with a further 26.09% reduction associated with increased inclusion rates of novel protein sources compared to 2024.
Outlook
Scaling cod and halibut production to 10,000 tons requires species-specific feeds that support growth, skeletal integrity, and overall health. Norway's goal of 25% self-sufficiency in sustainable aquafeed ingredients by 2034 further highlights the need for alternative raw materials. This work demonstrates how targeted feed innovation can enable emerging marine species and be transferable to species with similar nutritional requirements, such as spotted wolffish (Anarhichas minor).
Acknowledgement
Special thanks to Havland and Sterling Halibut for a fruitful long-year cooperation with strong knowledge sharing.
References
Hamre, K., Holen, E. and Moren, M. (2007). Pigmentation and eye migration in Atlantic halibut (Hippoglossus hippoglossus L.) larvae: new findings and hypotheses. Aquaculture Nutrition, 13(1), pp.65-80. https://doi.org/10.1111/j.1365-2095.2007.00467.x
Pedro, J., Henriques, J., Bergvik, M., Tzakris, K., Viegas, M., Loufi, K., Fernandes, J.M.O., Costas, B., Tokle, N. and Conceicao, L.E.C. (2025). Early nutrition impacts on growth, skeletal anomalies and organ ontogeny in larval Atlantic cod (Gadus morhua). Animals, 15(20), 2985. https://doi.org/10.3390/ani15202985
S��le, ��., Solbakken, J.S., Watanabe, K., Hamre, K. and Pittman, K. (2003). The effect of diet on ossification and eye migration in Atlantic halibut larvae (Hippoglossus hippoglossus L.). Aquaculture, 220(1-4), pp.683-696. https://doi.org/10.1016/S0044-8486(02)00584-7