industrialization has had adverse effects on the environment. through mining and burning of fossil fuels, acidic precursors are emitted into the atmosphere creating acid rain. acid rain is then deposited into freshwater lakes, causing lake acidification which can in turn affect the aquatic ecosystem. the purpose of this study was to investigate the effects lake acidification has on small-bodied fish across three lakes that were each subjected to acidification experiments in the iisd experimental lakes area. the effects of acidic deposition on small-bodied fish have not been widely studied. the prediction is that increased acidification in the lakes would lead to reduced small-bodied fish populations. abundance was measured against lake ph for each species to determine periods of chemical and biological recovery, as well as threshold limits for each fish. the findings show that most of the observed species did experience decline when acidification increased; however, slimy sculpin seemed to be more sensitive than the rest, while northern pearl dace abundance increased in response to acidification. further studies should be performed to determine absolute threshold values for species, including slimy sculpin and pearl dace based on the findings of this thesis.