Sustainable Aquaculture by Harnessing Medicinal Plants to Improve Growth, Immunity, and Lipid Metabolism
Global aquaculture has expanded rapidly to meet rising demand for aquatic protein, yet this expansion has been accompanied by intensified disease pressure and a corresponding reliance on antimicrobial chemotherapeutics, a practice now constrained by regulatory restriction and the spread of antimicrobial resistance. Medicinal plants and their derived phytochemicals have emerged as a widely investigated alternative, offering growth-promoting, immunomodulatory and metabolic benefits without the residue and resistance liabilities of synthetic drugs. This review synthesises evidence published between January 2015 and March 2026 on the dietary use of medicinal plants in finfish and crustacean aquaculture, with particular attention to three interlinked outcomes: growth performance, innate and adaptive immune function, and lipid metabolism. Botanicals such as Astragalus membranaceus, Moringa oleifera, Curcuma longa, Allium sativum, Zingiber officinale and Withania somnifera consistently improve weight gain, feed conversion, digestive enzyme activity and resistance to bacterial challenge across a range of species and rearing systems, generally through stimulation of lysozyme, complement and phagocytic activity, upregulation of cytokine and antioxidant gene networks, and modulation of hepatic lipogenic and lipolytic pathways such as SREBP-1c, PPARα and AMPK signalling. Effects are, however, markedly dose- and species-dependent, and excessive inclusion levels can suppress immune function rather than continue to enhance it. The review further considers the methodological heterogeneity of the underlying trials, the paucity of pharmacokinetic and long-term safety data, and the practical barriers to large-scale adoption, including standardisation of extracts and cost of production. It concludes that medicinal plants represent a scientifically credible component of sustainable feed formulation strategies but that their translation into commercial aquafeeds requires more rigorous dose-optimisation trials, harmonised reporting standards and mechanistic studies linking phytochemical composition to physiological outcome.