In this study we analysed the shape and topography of venomous glands in Brown bullhead (Ameiurus nebulosus) through MRI investigations. The main reason of this investigation was to provide a better understanding of the defence mechanism of this species. The presence, topography and structure of venomous glands made brown bullhead one of the top invasive species spreading its habitat worldwide. The specimens were collected from Stejeriş Lake, Cluj County. MRI investigations were conducted within the National Center for Magnetic Resonance (NCMR), Babeş-Bolyai University, Faculty of Physics. For anatomical investigations, RARE (Rapid Acquisition with Refocused Echoes) and Turbo RARE High Resolution protocols were used, based on the echo-type RF pulse sequence. In transversal sections, organs, blood vessels, and bone formations appear unchanged in shape, size, appearance and location. For the studied species, the venomous glands, together with the first radius of the pectoral and dorsal fins, as well as the muscular fascicles attached to the radius, are forming the venomous apparatus. Triangular positioning of pectoral and dorsal spines and also of their afferent venomous glands represents an efficient defensive mechanism against aquatic, terrestrial and aerial predators. Using MRI techniques for anatomical investigations of venomous glands in Brown bullhead proved to be very precise both in identifying the shape and the topography of the venomous glands. Also by using MRI techniques we highlighted the complex defence mechanism that Brown bullhead has developed against its natural predators.