Effects of Acid Rain On Fish

Acidity increase has an array of effects onto the individual fish as well as the population as a whole. Lowered pH levels increase aluminum levels that are directly toxic to fish. These changes cause chronic stress upon the fish lowering their body weight (Charles T. Driscoll).

At very low pH (3 or less) levels coagulation of mucous on gill surfaces and subsequent anoxia would the cause of death, however acidic levels are rarely this low. At less extreme pH levels (4-5) a disturbance of normal ion and acid- base balance may be the more likely cause of death. (Carl L. Schofield 1976)

Some species have a greater tolerance to acidic waters. But those most sensitive face a greater consequence. Often the young are most vulnerable and most fish eggs won’t hatch at a pH of 5 or less. (U.S Environment agency).

There has been observed decreased population density and a shift in size and age structure of fish due to increased acidity. Even a small increase of fish young fish mortality can be sufficient to decrease population and eventually lead to extinction. Often the decrease is not recognizable until the population is close to extinction (Schindler 1988). Spring-spawning fish face more exposure to a strong acid and aluminum pulse due to snowmelt, especially since the sensitive young fish are in shallow near shore waters. (Schindler 1988)

This table shows the pH level tolerance of certain aquatic species