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Failed fishery management

by Warren Illi
| January 11, 2024 12:00 AM

Sunday’s Daily Inter Lake had an interesting article about a Montana Fish, Wildlife and Parks proposal for what might be viewed as reinventing the wheel. The proposal is considering to restart a program to kill lake trout in Swan Lake.

Since many Daily Inter Lake readers may not have lived here long enough to know the history of fish management in Northwest Montana, let’s review some fish management history. 

Several years ago, Fish, Wildlife and Parks had a similar six- or seven-year project to reduce or eliminate the lake trout in Swan Lake because the lake trout were gobbling up young bull trout in the Swan River drainage.        

The Swan River drainage was or is a stronghold for the federally threatened bull trout. For those of us who love to hunt, fish, hike, camp and enjoy the great Flathead outdoors, wildlife including fish, are an important aspect of our outdoor experiences. For many of us, a fish is a fish is a fish. Probably doesn’t matter much if the fish species is the very common, non-native, good-eating yellow perch or a native, threatened bull trout that were here when early day explorers came through in the early 1800s.

For most fish species, nothing much changed until the 1890s.  But during the 1890s with the arrival of railroad transportation, fish species composition in Montana changed considerably. Those early day trains were steam powered. Right behind the engine was a water tank car to use to create steam to drive the locomotive. Right behind the water car was a car carrying coal or wood to fire up the engine.

Most of the railroads running through Montana originated in Minnesota where Northern Pacific Railway and the Great Northern Railway provided the initial railroad connection between the upper midwest and Seattle. 

Railroaders, being resourceful type folks, used their water tank cars to move their favorite fish species from the Upper Midwest to every stream and lake along the railroad to Seattle. There was no science involved. If a native western fish species was displaced by the newly planted fish from the midwest fish, so what! A fish was a fish. As long as the fish was fun to catch and good eating, that was good enough. 

This broad scale transfer of fish species from upper midwest waters to the west was done with the blessing of the new wildlife and fish agencies in North Dakota, Montana, Idaho and Washington. There was no differentiation between native and non-native fish species. No one seemed to worry about native species. 

As you can imagine, most of those early day fish plants failed because many non-native fish species couldn’t adapt to the habitat of western waters. But some of those early day, non-scientific, fish plants succeeded. 

A good example is the non-native lake trout now found in Flathead Lake. Those early day plantings of lake trout came from Lake Superior. They survived, but only multiplied in low numbers, because of the lack of a good supply of forage fish or food deep in Flathead Lake for the young lake trout. So those low numbers of newly introduced lake trout didn’t seem to impact native fish like the native bull trout. Lake trout prefer cool deep water. There was plenty of that kind of water in Flathead Lake, but there was not a good supply of small fish or fish food for the young lake trout deep in Flathead Lake. So only a few survived to become reproductive size adult size fish.

All that changed in the 1970s when mysis shrimp were introduced into the Flathead River system. The shrimp found their way into Flathead Lake and thrived. The shrimp were planted to expand the food base for Kokanee salmon, another non-native fish species. Similar mysis shrimp plants in Idaho resulted in great growth for Kokanee salmon. 

But that didn’t work in deep Flathead Lake. In fact, not only did the mysis not help the Kokanee salmon, but they literally wiped out this world class Kokanee fishery. Mysis are a day feeder and drop to the lake bottom at night. Guess what? When mysis dropped to the bottom of Flathead Lake, they encountered hordes of young starving lake trout. With this new food supply, the young lake trout survived and multiplied. When the lake trout grew big enough, they began to eat the Kokanee, wiping out Flathead Lake’s world class Kokanee fishery. 

What started as a plan to help the Kokanee ended by wiping out the Kokanee. Introducing mysis was well intended, but ended as a disaster for bull trout. Modern fishery management is still an evolving science. 

The abundant supply of lake trout in Flathead Lake eventually worked their way into Swan Lake where they began to eat the threatened bull trout. During a six or seven year period, FWP had an aggressive gill netting program in Swan Lake, trying to kill enough lake trout to allow more    young bull trout to survive, mature and run up the Swan River to spawn and reproduce. After a few years, that gill netting project was halted because gill netting was not appreciably reducing the lake trout in Swan Lake. Lake trout were reproducing as fast as they could be gill netted. So, the project was terminated.   

So here we are in 2024, considering the restarting of a failed fishery management program to kill off the nasty lake trout in Swan Lake to help the bull trout. It will be interesting to see what new fish management technology might be tried in Swan Lake.