The Efficacy of the African Annual Killifish Nothobranchius melanospilus in suppressing Malaria Vector Larvae

Malaria remains a major public health threat in sub‐Saharan Africa, with Anopheles mosquitoes (Meigen, 1818) as the principal vectors. Rising insecticide resistance necessitates sustainable, ecologically sound alternatives to chemical control. Although larvivorous fish offer a biological solution, introducing exotic species like Gambusia affinis (Baird & Girard, 1853) has caused ecological damage. This study evaluated the efficacy of the indigenous East African annual killifish, Nothobranchius melanospilus (Pfeffer, 1896), as a biocontrol agent against malaria mosquito larvae under controlled mesocosm conditions. A 25‐day experiment used 20 outdoor tanks (10 with N. melanospilus , 10 controls), each stocked with standardized populations of mosquito larvae (ML), soft‐bodied crustaceans (SBC), and hard‐bodied crustaceans (HBC). Prey abundance was quantified at the end of the experiment, and treatment effects analysed using t ‐tests and two‐way ANOVA. Tanks with N. melanospilus had significantly fewer mosquito larvae than controls (independent samples t ‐test: t (11.47) = 17.84, p < 0.001). The mean number of ML remaining was 82.0 ± 9.5 (mean ± SD) in control tanks compared to only 19.8 ± 3.7 in treatment tanks, representing a reduction of over 75%. A significant prey type × treatment interaction (two‐way ANOVA: F (2, 54) = 217.2, p < 0.001) showed mosquito larvae were disproportionately reduced, demonstrating high predatory efficiency and selectivity. Non‐target impacts on crustaceans were limited, indicating ecological compatibility. These findings highlight the ecological role of N. melanospilus as a native predator of mosquito larvae. Rather than advocating for active translocation or stocking, I propose that the most effective and sustainable strategy lies in conservation‐based mosquito control: preserving the seasonal wetland habitats where these fish naturally occur. Maintaining hydrological integrity and wetland health supports Nothobranchius populations and may indirectly contribute to sustained suppression of mosquito vectors.