How do you make sure that the pathologies being observed are solely due to the presence of heavy metals and not a complication of bacteria or other pathogens?
Do you study pathological effect of heavy metal in laboratory or in field conditions?If in the laboratory you must have a control group.But in field this is very complicated case becouse of many factors.Fish have MMC not only becouse of pathogens but also MMC serves as a indicator of stress (lack of oxygen or lack of food).