Fathead minnow egg production and hatching success at pH 5.3 was scant to non-existent. Eggs spawned and incubated until hatching at pH 8.1 and 6.3 produced 39.7 and 5.7% normal larvae, respectively; eggs spawned at pH 6.3 incubated at 5.3 produced 0.5% normal larvae. Reproductive failure at pH 5.3 may have been predicted by ovarian histology. Ovaries of fathead minnows at pH 5.3 had exceptionally high proportions of pre-ovulatory corpora atretica relative to other oocyte stages present. The fathead minnow data were generated as a basis of extrapolation to estimate reproductive impairment in smallmouth bass inhabiting acid environments by examination of their ovarian condition.