Control of common freshwater predatory fish, Channa punctatus, through Nerium indicum leaf extracts.

The diethyl ether, chloroform, acetone and methanol extract of Nerium indicum leaf were evaluated for their piscicidal activity against common freshwater air breathing predatory fish Channa punctatus. The rank of order of toxicity (LC50) of the leaf extract was, diethyl ether extract (17.34 mg/l)>acetone (40.01 mg/l)>chloroform (40.61 mg/l)>and methanol (106.37 mg/l). There was a significant negative correlation between LC50 values and exposure periods. Thus increase in exposure period, LC50 decreases from 17.34 mg/l (24 h) to >13.58 mg/l (96 h) in the diethyl ether extract. Similar trends were also observed in acetone, chloroform and methanol extracts. Exposure of sub-lethal doses (40% and 80% of LC50) of the diethyl ether extract of N. indicum leaf (which has maximum piscicidal activity) for 24 or 96 h caused significant alteration in the level of total protein, total free amino acid, nucleic acid, glycogen, pyruvate, lactate and activity of enzyme protease, phosphatases, alanine aminotransferase, aspartate aminotransferase and acetylcholinesterase in liver and muscle tissue. The alterations in all the above biochemical parameters were significantly (P<0.05) time and dose dependent. There was a significant recovery in all the above biochemical parameters, in both liver and muscle tissues of fish after the seventh day of the withdrawal of treatment. Thus, the leaf extracts of N. indicum have potent piscicidal activity against fish C. punctatus and also significantly affect both aerobic and anaerobic pathway of respiration in fish.