Lavi Jaiswal and Arvind Kumar Sharma

The present investigation was conducted to examine the chronic effects of sublethal concentrations of paper mill effluent on the freshwater fish Mystus vittatus, focusing on mortality/survival rate, relative growth rate (RGR), and rate of oxygen consumption. Based on the 96-hour LC₅₀ value of 8.223% v/v for Mystus vittatus, two sublethal concentrations were selected: 0.8% v/v (≈1/10th of LC₅₀) and 1.7% v/v (≈1/5th of LC₅₀). No mortality was observed at either concentration, indicating 100% survival. However, RGR declined progressively with increasing concentration and exposure duration. Similarly, oxygen consumption rate showed a significant decrease in effluent-exposed fish, with the reduction being more pronounced at higher concentrations and longer exposure periods. These findings suggest that the chronic toxicity response of experimental is strongly dependent on both effluent concentration and duration of exposure.

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