Abstract

The present study deals with the acute toxicity (LC₅₀ evaluation) of paper mill effluent to a freshwater fish, Mystus vittatus. A monthly record covering all the spawning season (pre-spawning phase, spawning phase and post-spawning phase) was evaluated at different exposure periods (24-, 48-, 72- and 96-h) using the whole paper mill effluent. Annual variation in LC₅₀ values in relation to annual breeding cycle and water temperature were also taken into consideration. A well marked variation in the LC₅₀ values in different exposure periods as well as in various months of the spawning phases of the test fish were observed.

Key words: Acute toxicity, paper mill effluent, annual variation, spawning phases.