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This experiment investigated the effect of dietary supplementation with essential oils from Artemisia afra and Moringa oleifera on haemato‐immunological parameters and resistance in Clarias gariepinus (African Sharptooth catfish) (Burchell, 1822) challenged with Aeromonas hydrophila. The experiment lasted for 45 days. Prior to and postchallenge, white blood cells significantly increased (p < .05) from the 3% to 12% M. oleifera and A. afra supplementation. Pre‐challenge, no significant differences (p > .05) in red blood cells, haemoglobin and haematocrit were observed between the control and M. oleifera supplementation, while in the A. afra supplementation, RBC and HCT significantly increased from the 6% to 12%. Postchallenge, RBC, HGB and HCT were significantly lower (p < .05) in the control and the 3% and 6% M. oleifera and A. afra supplementation. Both pre‐ and postchallenge, nitro‐blue tetrazolium levels significantly increased (p < .05) from the 3% to 12% M. oleifera supplementation while no significant differences (p > .05) were observed in lysozyme activity between the control and treatment groups. In A. afra, NBT and lysozyme activities increased significantly (p < .05) from the 6% to 12% supplementation pre‐ and postchallenge. Survival rate increased from the 3% to 12% in M. oleifera and A. afra supplementation groups. Significant kidney histological alterations were noted in the control and the 3% and 6% supplementation of both plants postchallenge, while no major histological changes were observed between treatment groups and the control pre‐challenge. The results demonstrate that EO from M. oleifera and A. afra can improve immunity and enhance survival in C. gariepinus.

Mozambique tilapia (Oreochromis mossambicus) and the African Sharptooth catfish (Clarias gariepinus) are the most farmed freshwater fish species in Southern Africa. However, production in the freshwater aquaculture sector has remained low due to, among other key factors, high cost of feeds, disease outbreaks, and poor sexual development in broodstock. Small-scale farmers are affected the most because they often lack resources and cannot afford expensive commercial diets, antimicrobials, and synthetic hormones needed to regulate reproduction. Among the proposed solutions, the inclusion of medicinal plants as feed additives is the most promising alternative to enhance growth performance, disease resistance and reproduction in fish. Plants contain various compounds such as polyphenols, carbohydrates, amino acids, flavonoids, alkaloids, tannins, organic acids, volatile oils, polysaccharides, minerals, and vitamins, some of which are necessary for growth and improving immunity or overall wellbeing in fish and other animals. However, the utilization of plants as feed additives in aquafeeds is still limited in Southern Africa. This paper reviews the potential role that medicinal plants can play as feed additives in order to promote growth performance, immunity, disease resistance, and reproduction in the culture of O. mossambicus and C. gariepinus in Southern Africa. The objective was to consolidate information about plants that can be specifically applied in freshwater aquaculture in Southern Africa by highlighting their availability and efficacy as either growth promoters or immunostimulants or fertility enhancer.