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Mercury was discovered in every sample of two fish species—the speckled dace and fathead minnow.

The EPA stated in 2011 that it  plans to retain personnel to “protect the physical integrity of the test organisms,” like the fathead minnow, which it uses in toxicity studies.

Purdue University researchers raised fathead minnow embryos in water taken from two Indiana streams that are contaminated with natural and synthetic hormones from manure spread on fields.

At the same symposium, Dan Rearick, an aquatic toxicologist from St Cloud State University in Minnesota, reported that a chemical found in birth-control pills, 17-β-estradiol, reduced the ability of fathead minnow larvae to elude predators.

Small muddy streams were preferred by P. promelas; however, the fathead minnow was taken in all habitats, and in association with most other species.