All water bodies and all fish are contaminated with mercury from atmospheric sources, but some contain high amounts of mercury while some contain low amounts. The states invest considerable effort and resources into monitoring the fish in public rivers and lakes to determine which water bodies contain fish that are highly contaminated with mercury. However, there are too many water bodies for the state agencies to sample each individual site and many are located on private land and are not monitored. For example, in the south central U.S., there are millions of small water bodies like creeks and farm ponds.

The chance of catching and eating a fish with high levels of mercury depends on three factors:

  • where the fish was caught
  • the type of fish
  • the size of fish

A new tool to estimate mercury contamination in fish

We have estimated mercury concentrations in fish using a model developed by the USGS. You can select the area where your fish was caught, the type of fish and size of fish to see estimates of mercury concentrations. This tool allows you to determine if fish caught in the south central U.S. are highly contaminated with mercury.

How to use this tool to estimate mercury contamination in fish

Click on your fishing spot within the purple-shaded area on the map below:

What are the purple-shaded areas on the map?

Each of the shaded areas on the map above is a different ecoregion – an area of the environment that shares similar landscape characteristics. Our research has shown that mercury contamination of fish varies with ecoregion type in part because of differences in forest coverage.

How do I interpret this information?

Ecosystem averages may not reflect concentrations of mercury in fish at specific water bodies. Specific waterbodies may have concentrations of mercury in fish that are higher or lower than the ecosystem average. For large public water bodies, there may be fish consumption advisories issued by the states.

Our lab is willing to determine mercury in fish for individuals. The whole fish will have to be sent to us frozen. Please contact us if you would like help in determining the mercury concentrations of fish in a specific water body.

In the absence of other information, a good rule of thumb to follow is: the bigger the fish and the higher up in the food chain the species is (i.e. more predatory), the higher the mercury concentration.

Sources of Information

For more information about our mercury research, go to our Aquatic Ecology Lab website.