Glacier Park fish safe to eat

If you catch a cutthroat trout in Glacier National Park, it's a fairly safe meal, Park fisheries biologist Chris Downs said last week.

Downs said the Park recently tested several different species of fish for mercury levels. What it found was that mercury in cutthroat trout was fairly low - safe for humans and for wildlife. Other species, like northern pike, had elevated levels of mercury, but even those levels were fairly low.

Mercury is a toxic metal that's spread to Glacier Park through the atmosphere as methyl mercury. About one-third of airborne mercury is natural and the other third is caused by industrial pollution - namely burning coal.

Mercury levels "biomagnify" in fish, following the food chain. For example, zooplankton in water may have trace amounts, but then the plankton is eaten by small insects, who concentrate it in their bodies, the insects are eaten by fish, and the fish are eaten by bigger fish.

So elevated levels in northern pike make sense, Downs notes, because they prey on other fish throughout most of their life cycle.

According to the Park's tests, northern pike in Sherburne Reservoir, 32 to 40 inches in length, had the highest concentrations of mercury.

But cutthroat trout from other waters had low levels of mercury - about one quarter as much as the pike.

In addition, literature suggests that selenium in ecosystems - at least at low levels - binds with low levels of mercury, lessening its effects in the food chain, Downs noted. Glacier Park seems to have the right balance of selenium, he said.

There are still concerns in the Park. The Western Airborne Contaminants Assessment Project in 2008 looked at contaminants in national parks across the country, and Glacier Park had some of the highest levels of DDE, chlordane and Dieldrin.

DDE is a breakdown product of DDT, a pesticide that was banned long ago. Chlordane and Dieldrin are banned pesticides as well. It's thought that because Glacier Park is downwind from farming in Washington State, the pesticides persist in the Park, carried by the prevailing winds.

Downs noted that looking at those contaminants and how they could be impacting Glacier Park's wildlife and food chains is ripe for further study.

There is one catch to eating a trout in Glacier Park. In almost all Park's waters west of the Continental Divide, it's catch-and-release only for westslope cutthroat trout. The same is true outside the Park on the North and Middle forks.

To view all of Glacier Park's fishing regulations, visit online at www.nps.gov/glac/planyourvisit/fishing.htm.