Mack search in Glacier has implications for Swan

Hungry Horse News

Research on lake trout in Glacier National Park could help the feds control the non-native fish in other lakes as well, a federal fisheries biologist said last week.

In the summers of 2003 and 2004, Andy Dux, of Montana State University's fishery research unit, netted and radio-tracked lake trout in Lake McDonald on the park's west side.

Lake trout are not native fish west of the Continental Divide. They were introduced into Flathead Lake decades ago, and since then they've been blamed for putting a huge dent in native species populations like bull trout, where they compete for food and space in local lakes.

Among other things, Dux found that the non-native lake trout spawned in specific habitats in Lake McDonald, said Wade Fredenberg a biologist with the U.S. Fish and Wildlife Service.

In fact, Fredenberg said, Dux's research found that in Lake McDonald the trout were looking for spawning habitat that was so specific-a mix of large clean cobble rocks-that they were literally stacked up on one another.

"Andy was able to narrow down to a huge extent" where lake trout were spawning, Fredenberg said last week.

That finding is significant if you're trying to eradicate lake trout from a lake, because if they're all congregated in one area, then they are far more vulnerable to netting operations than trying to net out a huge lake like Lake McDonald.

Pinpointing the fish is possible because of relatively new advancements in technology. Radio tracking systems are very small now, and the electronics are much better. Also, cameras have been developed that biologists can just drop off the side of the boat to watch what the fish are doing.

"The real significant aspect is that we can use modern-day technology to narrow down the habitat we can exploit," Fredenberg said.

The park and the wildlife service floated the idea of netting lake trout in Lake McDonald a few years back, but the project died for a lack of funding.

Now Fredenberg sees the possibility of doing similar lake trout tracking-and eventually netting-in Swan Lake.

Swan Lake is regarded as one of the last bastions for bull trout populations in Montana. But lake trout have been found in Swan Lake, and they are reproducing. The fear is if they are left alone, unchecked, they'll ruin the bull trout fishery there as well.

Fredenberg said interested agencies have begun serious talks about controlling lake trout in Swan Lake. The hope is that lake trout in the Swan are also congregating to spawn in specific habitat where they can be netted relatively easily.

One thing is for certain- the lake trout are expanding in Swan Lake. It was just a few years ago when lake trout were discovered in the lake.

Now juvenile fish are already being found, meaning the adults are reproducing.