acute toxicity evaluation of five herbicides: paraquat, 2,4-dichlorophenoxy acetic acid (2,4-d), trifluralin, glyphosite and atrazine in luciobarbus esocinus fingerlings

background: evaluation of herbicide pollution in aquatic environments needs the great concern and the most important echo-pollutant effects of herbicides are related to their effects on non target aquatic organisms. native fish can serve as a proper bio-indicator for evaluation  of pollution on aquatic ecosystems. objectives: to find environmentally friendly herbicides, in this study the acute toxicity of five widely used herbicides in iran as aquatic ecosystems pollutants on luciobarbus esocinus were investigated. methods: acute toxicity (96 h lc50) of five herbicides (paraquat, 2,4-dichlorophenoxy acetic acid, trifluralin, glyphosite and atrazine) were determined via oecd standard method. l.esocinus exposed to serial concentrations (more than 6 in triplicates) of each herbicide. mortalities at 24, 48, 72 and 96 hours after exposure were recorded and the lc50 were calculated using probit software. results: results showed that acute toxicity of these herbicides are significantly different in l. esocinus. the 96 h lc50 of paraquat, 2,4-d, trifluralin, glyphosite and atarzine in l.esocinus were 54.66, 138.8, 1.09, 716.83 and 44.30 mg/l respectively. glyphosite showed lowest toxicity in luciobarbus esocinus among the five herbicids. the highest toxicity of herbicides in l. esocinus belongs to trifluralin. the mortality rate of exposed fish to herbicides enhanced either by increasing herbicides concentration or duration of exposure. mortality patterns during 96 hours of toxicity evaluation were similar in all five herbicides. conclusions: regarding the high application and similar efficacy of  herbicides in most of the cane farms of khouzestan province, and based on different toxicities of these five herbicides for fish as a non targeting organism, glyphosite is highly recommendable as a proper alternative to trifluralin, atrazine, paraquat and 2,4-dichlorophenoxy acetic acid.