Excess eutrophication of aquacultural ecosystems has been a prolonged threat to the fishing industry worldwide. Strategies like manual and mechanical weed removal from eutrophic ponds are costly and ineffective, particularly for larger complicated ecosystems. So the use of effectual herbicides and algaecides has become popular among aquaculturistsas a relatively easy and cost-effective method to minimize eutrophication. Paraquat has been used as a popular aquatic herbicideacross the globe. When utilized in the aquatic environmentParaquat exhibits a high affinity toward the hydrosoil and bottom sediments. Once absorbed at the bottom, Paraquat persists there for longer periods. Hence the study of the effect of Paraquat on a bottom feeder species was important to reveal baseline data.Cirrhinus mrigala is an economically important freshwater Indian Major Carp, extensively reared as a bottom feeder in integrated fish farming throughout Southern Asia. As a benthic feeder, this species is highly susceptible to being exposed to Paraquat residues persisting at the bottom of fish ponds. Hence it was chosen as a test animal.The present experiment was designed to study the effects of sub-lethal concentrations of chronic Paraquat exposure on total protein, total lipid, and total glycogen contents in fishCirrhinus mrigala.During the experiment, the fishesin different sets were exposed to 1/20th and 1/10th concentration of the Median Lethal Concentration (LC50) along with their respective control groups for 30 days using static renewal bioassay apparatus. Post-exposure, vital tissues like gill, muscle, liver, and brain were pooled out separately from live fish and the total protein content was measured by Lowry’s method (1951), total lipid content was measured by Barnes and Blackstock method (1973), and total glycogen content was measured by Dezwaan and Zandee’s method (1972). Annotated results represented that, the total protein content in the 1/20th group showed a significant (p<0.05) decrease in the gill and brain tissue while in the 1/10th group it showed a moderately significant (p<0.01) decrease in the muscle, liver and brain tissue and significant (p<0.05) decrease in the gill tissue. The total lipid content in the 1/20th group showed a moderately significant (p<0.01) decrease in the gill tissue and a significant (p<0.05) decrease in the liver and brain tissue while in the 1/10th group gill and liver showed moderately significant (p<0.01) decrease and the brain tissue showed significant (p<0.05) decrease. The total glycogen content in the 1/20th group showed a moderately significant (p<0.01) decrease in muscle tissue while a significant (p<0.05) decrease in gill and liver tissue while in the1/10thgroup it showed a highly significant (p<0.001) decrease in muscle tissue, moderately significant (p<0.01) decrease in the gill and brain tissues and significant (p<0.05) decrease in liver tissue. All activities were compared with their respective control groups to derive the level of significance of the decreased content. In conclusion, alterations caused in the biochemical parameters of fish due to sub-lethal exposure to Paraquat suggest Paraquat as a potential Eco-toxic agent causing severe environmental pollution. The decrease in the level of protein, lipid, and glycogen content can be directly linked with the overall reduction in the weight of marketable fish causing economic losses to fish farmers.

Paraquat Dichloride, Cirrhinus mrigala, Chronic Toxicity, Biochemical Alterations, Environmental Pollution.