Toxicity and bioaccumulation of chromium in some freshwater fish

Chromium (Cr) is a common pollutant of freshwater bodies in India, and is frequently detected in high concentrations in edible fish. Bioassays were carried out in the laboratory to determine acute the toxicity and pattern of accumulation of Cr in three species of freshwater fish. The 96-h LC₅₀ value of Cr for Labeo bata, Puntius sarana, and Catla catla was found respectively as 7.33, 10.37, and 31.61 mg/L. Concentrations of Cr in water, sediments, and fish, during a period of 28 d of exposure to 0, 0.73, and 2.19 mg/L of Cr, varied with exposure period, concentration of Cr, presence of weed, and species of fish exposed. Polynomial regressions obtained by drawing polynomial curves revealed that the aquatic weed Eichhornia crassipes prevented gradual decrease of Cr concentrations in water, but reduced the accumulation of Cr in L. bata and Catla catla. However, the effect of the weed on Puntius sarana was not apparent. The pattern of Cr deposition on sediments was also inconsistent. To explain interactions between environment and fish in a very precise manner, polynomial and multiple regression curves were simultaneously used. When polynomial curves were replaced by multiple regression curves, it was revealed that the aquatic weed E. crassipes could reduce Cr accumulation in Puntius sarana also.