Biomonitoring of metals in fish and their parasites: an update

Metal stress is one of the major concerns and persistent monitoring of the issue is the need of the hour. Urban domestic waste, agricultural runoff, industrial waste, and mining waste are anthropogenic sources of metals apart from natural sources. Specifically, the aquatic ecosystem including flora and fauna is under great threat due to metal discharges. Aquatic species, such as algae, fish, and associated parasites, are severely damaged due to metal pollution in turn affecting human beings through the food chain. To avoid this crisis, bioremediation is one of the best solutions. To perform bioremediation experiments, it is essential to monitor both flora and fauna near metal-rich areas. Hence, this review intends to summarize the developments in the biomonitoring of metals in fish and their parasites. The physiological, histopathological, biochemical, and molecular changes observed in both fish and their parasites grown in metal-rich water bodies were emphasized. Information on lethal doses and certain bioindicators were also highlighted in this review. This work will be useful to know the metal accumulation capacity of fish and their parasites, future bioremediation research using aquatic animals, and also helpful for fish industries.