Sustainable aquaculture development in Sweden: An assessment of novel feed in aquaponic cultiva tion of Nile tilapia

Abstract

As the global population continues to rise, the demand for resilient and resource efficient food production is becoming increasingly urgent. Aquaculture is the fastest growing food sector, although transitioning to low-impact practices requires innova tive strategies to reduce dependence on conventional methods. One major bottleneck in aquaculture is the reliance on conventional feed ingredients such as fishmeal andsoy protein. Another challenge is nutrient loss from these systems, which not only contributes to environmental pollution but also represents a waste of valuable re sources. To make aquaculture truly sustainable, a shift toward circular, sustainable systems is important. This study compared a regionally available alternative feed, based on mussel meal and pea protein concentrate, to a conventional feed contain ing fishmeal and soy protein in aquafeeds for Nile tilapia (Oreochromis niloticus) reared in coupled aquaponic systems. An experiment was set up to compare fish performance, water quality, plant growth, and microbial activity between trials of conventional diets and alternative diets. Fish reared in aquaponic systems exhibited high growth and feed efficiency when fed the alternative diet (FCR: 1.07), performing slightly below the commercial control feed and the fish in recirculating aquaculture systems (RAS), although still within acceptable limits (FCR: 0.90 - 1.80). Once nu trients began to accumulate during the stabilization phase, the aquaponic systems maintained stable water quality and supported Tatsoi (Brassica rapa) growth that was comparable to, or even greater than that of the hydroponic control systems, throughout the feeding trials. Microbial assessments and cortisol analyses indicated that aquaponic systems supported fish welfare comparable to that of RAS. When fish were fed the alternative feed, microbial loads were generally lower in both rearing systems compared to those fed the conventional diet. Overall, the findings support the potential of blue mussel and pea protein as sustainable feed components in in tegrated aquaponic production, contributing to nutrient circularity and reducing dependence on limited marine stocks and imported resources.