Hebgen Lake Mercury Filter: Brett French Radio Show Preview
By Matt Schauer

Posted: December 14, 2012

A recently published study is shedding light on something that most Montana anglers may not be aware of: that Hebgen Lake acts like a huge filter to remove mercury from the Madison and Missouri river systems.

The study was done by the U.S. Geological Survey and Montana Fish, Wildlife and Parks researchers. They took samples from the water, lake sediment and fish flesh and had them tested for mercury. Mercury is a toxic chemical that is especially dangerous to young children and developing fetuses. The toxin occurs naturally in the environment but is released at higher-than-usual concentrations from Yellowstone National Park’s geysers and hot springs. Those thermal features flow into the Firehole and Gibbon rivers which form the headwaters of the world-famous Madison River. Much of that mercury dissipates or settles in Hebgen Lake, making the water below the dam much cleaner than it would otherwise be.

Mercury also comes from coal-fired generating plants, mines and industrial runoff.

The state has long alerted anglers to the possible dangers of eating fish contaminated with mercury. The danger is higher for young children and pregnant women. A list of waters in the state where mercury and PCBs are known to exist can be found HERE: The Fish Consumption Guide DRAFT. A chart lists each water body where the contaminants are known to exist and the recommended amounts of fish that can be safely eaten. As the chart points out, larger fish carry more contaminants because they build up over time in the fish’s flesh. So eating smaller fish is healthier. Brown trout were also found to contain more mercury than rainbow trout, probably because they are more predatory.

This is yet another reason to release that trophy fish you catch after taking a photo.