Globally, aquaculture is a rapidly growing food sector due to increasing demand for seafood. However, using marine-derived forage fish like anchovies and sardines for fishmeal (FM) and fish oil (FO) in aquafeeds, especially for salmonids—the most significant users—has raised sustainability concerns. These concerns have led to the exploration of sustainable a lternative aquafeed ingredients. Microalgae represent a more environmentally sustainable alternative because they can be produced in large quantities on controlled nonarable land, contain high protein and long-chain fatty acid profiles , and typically do not compete with human food products. We report our recent study to develop aquaculture feed formulae using defatted co-product biomass left over after commercially raising microalg a, Nannochloropsis sp., to produce a nutraceutical.
Data from our recent experiments show comparable growth, filet composition, feed conversion, and survival of rainbow trout fed a diet entire ly replacing FM with Nannochloropsis sp. co-product. We first determined the nutrient digestibility of the co-product . We then conducted a 64-day nutritional feeding experiment to determine the optimal level of FM replacement for growth and filet fatty acid composition. We finally used the Cruz Aquafeed Sustainability Tool to determine the diets’ economic conversion ratio (ECR; feed cost per kg of fish produced) . The digestibility study showed that the raw Nannochloropsis sp. co-product diet had higher protein and energy values. The growth study results showed that trout fed 100% FM replacing the diet with the raw co-product did not significantly differ from fish fed the reference diet in feed conversion ratio, growth, and survival rates. The analysis of the ECR results showed no significant differences between the diets. Thus, utilizing Nannochloropsis sp. co- product in trout feed can completely replace FM while maintaining rainbow trout’ s growth performance, flesh composition, and cost viability at levels similar to the fish fed diet.