In this paper, a nonlinear mathematical model is proposed and analyzed to see the indirect effect of air pollutants on the prey-predator type fish population in a closed population (lake). It is shown that as the pollutant concentration in the environment increases, the concentration of the acidic chemicals in the lake increases and consequently the equilibrium level of the fish population decreases. Using stability theory of differential equations and computer simulation, it is shown that due to the effort, pollutant concentration can be reduced to a desired level to save fisheries from extinction by acid rain.