Inhabits muddy pools of headwaters, creeks and small rivers. Also found in ponds. Tolerates unsuitable conditions (e.g., turbid, hot, poorly oxygenated, intermittent streams). Interannual population density varied dramatically in response to the severity of the preceding winter for species inhabiting boreal lakes in Alberta, Canada (Ref. 77054). Populations from two shallow lakes repeatedly winterkilled, 47-94% post winterkill declines in density, increased growth rates of the surviving fish (Ref. 77054). Maintained a relatively high metabolic rate and level of activity under hypoxic conditions (Ref. 77050). Individuals that survived the hypoxic conditions during winter had rapid growth rates after ice-off (Ref. 77048). Responds to visual and chemical cues of northern pike, Esox lucius. Species found in naturally predator-free waters learned to avoid the 'scent' of introduced pike faster than the sight of them (Ref. 77049). Anti-predator responses by fathead minnows increased with higher concentrations of chemical "odor" emitted from northern pike. More frightened by the cues of smaller-sized pike, which may pose a greater predation threat than larger pike (Ref. 77062).