Benefits of the microalgae Spirulina and Schizochytrium in fish nutrition: a meta-analysis

Abstract

AbstractUse of microalgae in fish nutrition can relieve pressure on wild fish stocks, but there is no systematic quantitative evaluation of microalgae benefits. We conducted a metanalysis on the nutritional benefits ofSpirulinaandSchizochytriumas replacements of fishmeal and fish or plant oil, respectively. We reviewed 50 peer-reviewed studies involving 26 finfish species and 144 control vs microalgae replacement comparisons. Inclusion ofSpirulinain the fish diet significantly improved growth compared to controls (SMD = 1.21; 95% CI 0.71–1.70), while inclusion ofSchizochytriummaintained the content of omega-3 PUFA of the fish fillet compared to fish fed on fish or plant oils (SMD = 0.62; 95% CI − 0.51–1.76). Benefits were apparent at replacement levels as low as 0.025% in the case ofSpirulinaand 10% in the case ofSchizochytriumoil. Dose-dependent effects were found forSpirulinareplacement on growth, but not forSchizochytriumon omega-3 fillet content. Subgroup analysis and meta-regression revealed that ~ 24–27% of variation in effect sizes can be accounted by variation between fish families, the rest likely reflecting variation in experimental conditions. Overall, the evidence indicates thatSpirulinaandSchizochytriumreplacement in aquafeeds can be used to improve fish growth and maintain fillet quality, respectively, but considerable uncertainty exists on the predicted responses. To reduce uncertainty and facilitate the transition towards more sustainable aquafeeds, we recommend that feeding trials using microalgae are conducted under commercially relevant conditions and that greater care is taken to report full results to account for sources of heterogeneity.