Isolation and Identification of Pathogenic Fungi from Freshwater Fish Mastacembelus armatus

Microbiological investigations were conducted on Mastacembelus armatus (Lacepède, 1800) samples from a local fish market in the Bundelkhand region to isolate fungal pathogens associated with diseased tissues. Fish exhibiting open wounds and ulcerative lesions on the caudal region and gills were selected. Infected tissues were aseptically excised, homogenised, and serially diluted up to 10⁻³. Dilutions were streaked onto Potato Dextrose Agar (PDA) and incubated at 28 °C for fungal isolation. Purified cultures were obtained via repeated subculturing, and morphological identification was performed using lactophenol cotton blue staining. Fungal species isolated included Aspergillus flavus, A. niger, A. ruber, Penicillium decumbens, Cladosporium sp., Rhizopus stolonifer, and Trichoderma viride, with Aspergillus species predominating (~50% of isolates). Identification was based on cultural and microscopic characteristics using standard taxonomic keys. The study indicates fungal infections in M. armatus are linked to environmental conditions, including contamination, eutrophication, and anthropogenic pressures in the Pahuj River. Regular water quality monitoring and effective management are recommended to protect aquatic biodiversity and ecosystem health.