Unintended consequence: Screwing up the native fish population in Flathead Lake.

Method: Trying to feed them.

This is gorgeous Flathead Lake, about 100 miles from Missoula, Montana. It is one of the cleanest, most pristine lakes in the world. Bigger than Lake Tahoe, Flathead Lake is the largest natural freshwater lake west of the Mississippi River (in the lower 48.)

Flathead Lake is famous for its clear water. You know all those cool shots on Tumblr of really clear water? Many of those were taken at Flathead Lake:

Since it's so gorgeous, as well as home to lots of very cool species of fish, the lake is a huge attraction for fishermen and brings in beaucoup tourist bucks for the state.

In 1905, TPTB (The Powers That Be ) thought it would be a great idea to introduce Lake Trout to Flathead Lake.

For decades the Lake Trout existed as a minority fish species alongside the native Westslope Cutthroat Trout:

and the (now endangered) Bull Trout:

Things went along swimmingly in Flathead Lake for most of the 20th century.

Then, about 30 years ago, TPTB had another good idea. They thought that fat fish would equal happy fish, so they introduced Possum Shrimp into Flathead Lake as an additional food source for all those trout.

The problem was that Possum Shrimp were sort of ambitious. They didn't want to be just a trout treat. They wanted to eat, too. Their food of choice was Water Fleas.

And they didn't eat just a handful here and a handful there, those Possum Shrimp devoured Water Fleas to the point that other smaller organisms took over the fleas' spot in the ecosystem. This threw everything off.

It turned out that the native Westslope Trout and the Bull Trout really didn't care too much for Possum Shrimp, but the non-native Lake Trout just adored them. Soon the foreigners (the Possum Shrimp and the Lake Trout) were taking over, crowding out the native trout, which are now struggling to survive. And what's more, the Lake Trout have now taken to traveling up to the streams in the Glacier Park area, which is worrisome for the ecosystems up there.

The experts are attempting to extricate Flathead Lake from the decline of its native fish population, but efforts thus far have been expensive and largely futile.

Certainly this is a sad example of the law of unintended consequences.

(I already knew this story from dating a graduate assistant involved in studying Flathead Lake, but my memory was jogged by looking through the Wikipedia article on the lake and by reading a story in Popular Mechanics about current eradication efforts directed toward the Brown Trout and the Possum Shrimp. All photos from the Internet.)