Significance

• The fathead minnow is an extremely hardy fish with a rapid rate of reproduction. It can tolerate low oxygen levels, muddy water and a wide range of pH levels, even those inhospitable to other fish. Due to its hardiness and ease of breeding, the fathead minnow is the preferred fish for toxicity testing under U.S. Environmental Protection Agency guidelines.
  
  

Benefits

• According to "Aquatic Toxicology" at ScienceDirect.com, the fathead minnow is an excellent model for toxicology testing. It helps scientists identify how chemicals work on organisms at various life stages. The minnow's fast and reliable reproduction rate ensures that it can be produced in large numbers for laboratory use, and its hardiness enables the fish to be shipped over large distances.
  
  

Types

• Scientists perform several different types of toxicity tests using the fathead minnow. These include freshwater chronic toxicity tests, which expose fathead minnow larvae to different concentrations of a substance for seven days, 48-hour lethality tests and both full and partial life-cycle toxicity tests. These tests are routinely used by regulatory programs to determine the potential risks of new chemicals. Test results are based on the weight and number of surviving fish at the end of the test.
  
  

Expert Insight

• According to the South Dakota Department of Environment & Natural Resources, all fathead minnow toxicity tests use strict protocols for testing. These include the light quality and intensity, temperature of the tank, amount of dissolved oxygen in the water and other conditions. This ensures that tests done at different laboratories will produce similar results and reduces the risk of outside factors, such as heat or light, influencing the growth of the minnows.
  
  

Considerations

• The fathead minnow's hardiness makes it an easy fish to use in the lab, but it may not make it the ideal species for determining a chemical's toxicity to other animals. Some creatures, such as amphibians, are much more susceptible to environmental toxicity than the fathead minnow and cannot survive the same conditions. Because of this, fathead minnow toxicity tests should not be the only method used to determine the safety of a chemical in an aquatic environment.