Selenium, in lesser amounts, is an essential part of life

There has been a lot of headlining in the recent days about selenium, coal mining, the Flathead and the Kootenai River drainages. What does all that mean to the anglers at Koocanusa and the Kootenai River?

Let’s start with what selenium is and what it does: It is found just about everywhere in the soil and rocks but usually in very small amounts. It is more common in the rocks of some areas including coal deposits. When the ground is disturbed at coal mines like those in the Elk River valley in British Columbia, selenium in its many forms becomes exposed to the environment. Selenium is fairly heavy so it won’t stay airborne, but through snow/rain/runoff it finds its way into the Elk River and eventually into Lake Koocanusa.

In small amounts, selenium is an essential element of life for both plants and animals. Selenium is taken in through food chain transfer rather than directly through the water. What that means is that plants like the tiny planktons and algaes absorb it from the water as they grow; they get eaten by microscopic animals and insects which, in turn, get eaten by fish and those fish by other fish. Each time that process occurs the selenium stays with the larger organism or “bio accumulates.” If animals accumulate selenium in their bodies faster than it can be used then it can become toxic. For fish, very high selenium levels become apparent when the newly hatched fry are deformed, sometimes enough so they don’t survive. In humans  — remember these are at very high levels — common symptoms may include effects to the thyroid, skin and hair.

So what’s the bottom line? The level at which the EPA recommends controlling how much fish you eat begins at 1.5 grams of selenium per kilogram dry weight of the fish. That is parts per million once all the water has been removed from the tissue sample. Montana Fish, Wildlife and Parks, Montana Department of Environmental Quality and others sampled most of the different fish species in Koocanusa in 2008. The good news is that selenium levels in kokanee, rainbow trout and whitefish that we analyzed were considerably below the threshold. We have not sampled those species downstream of Libby Dam but, for now, we believe the levels are similar to those in Lake Koocanusa.

Burbot were an exception. Selenium levels were high enough that MFWP decided there should be a consumption advisory for burbot caught in Lake Koocanusa. We have not completed the advisory yet but I recommend no more than four fish per month. We need more information, but high selenium levels may also be a contributing cause for why the burbot population has remained so low in Koocanusa. The groups I mentioned have created a plan to continue monitoring selenium levels in the fish, water and sediments in Lake Koocanusa starting this spring.

To get more information about consumption advisories for Koocanusa and other waters in Montana check the MFWP website at fwp.mt.gov; click on Fishing then look near the bottom of the left-hand column to find Fish Consumption.

(Mike Hensler is a fisheries biologist in Libby with the Montana Department of Fish, Wildlife & Parks)