Edible Fungi in Functional Aquafeeds: Prebiotic and Immunostimulatory Effects in Commercially Important Farmed Fish

Abstract

Simple Summary Fish farming must increase production while reducing reliance on fishmeal, fish oil and antibiotics. Edible fungi, such as oyster, shiitake and reishi mushrooms, contain bioactive compounds that may support intestinal function, feed utilization, and innate immune responses in fish. This review examines how edible fungi and fungal-derived compounds, especially β-glucans and chitin, may contribute to gut microbiota modulation and immune stimulation in diets for commercially important fish. The available evidence indicates that their biological effects depend strongly on the fish species, ingredient form, dietary inclusion level, processing method and experimental conditions. Omnivorous fish such as tilapia generally tolerate broader inclusion levels, whereas carnivorous salmonids appear to respond more consistently to low dietary levels of extracts or processed fractions. Therefore, edible fungi should be regarded as complementary functional ingredients rather than simple protein replacements, requiring species-specific formulation strategies, standardized ingredient characterization, and validation under commercial farming conditions.