Trout tags reveal migration, spawning and reliance on cold water habitat

Montana Fish, Wildlife & Parks biologists hope anglers will want to play tag this summer.

On a weekday afternoon, FWP fish biologists Ladd Knotek and Patrick Uthe headed one last time to the fish ladder at Rattlesnake Dam to check for trout. Knotek and technician Reuben Fruy have checked for trout in the fish ladder every day for the past two months, knowing spring is when rainbow and Westslope cutthroat would be trying to fight their way upstream to spawn.

The fish ladder has a series of stepped pools that make it easy to catch fish when the water is turned off from above. But that convenient spot will disappear in a few weeks as demolition begins on Rattlesnake Dam.

“(This project) isn’t directly related to the dam removal project,” Knotek said. “But once they take the dam out, the best chance to catch fish is at the (creek) mouth. That’s why we were hoping to put a lot of effort in while we still had this.”

Any trout the duo could catch would end up with a colored wire sticking out of its back before being released above the dam to continue its journey.

Over the past two months, the two have attached orange tags to about 180 trout in Rattlesnake Creek. But that’s just how they’d end their day. They’d also travel to fish traps on Deer and Marshall creeks while Uthe and his crew were doing the same on four creeks in the Blackfoot drainage.

The idea to tag fish to learn of their travels had started with Rattlesnake Creek, but Knotek and Uthe decided to take it further.

“We might as well do it right; might as well go big,” Knotek said. “If you’re going to go out and check traps anyway, you might as well do a bunch of streams in the same area.”

All told, they tagged about 800 fish. Trout in each creek got a different color tag so biologists know where they were caught.

“This is pretty much the end,” Knotek said. “We’re worn out – it’s time to have a real weekend.”

While it may be ending for FWP biologists, work is just beginning for volunteers at Montana Trout Unlimited. Once the streamflows drop and the water clears, anglers will get out on the rivers. And with 800 tagged fish that could potentially be caught, biologists want to know where they are hooked.

When Trout Unlimited Project Manager Rob Roberts learned of the project, he knew TU had the resources to get the word out to anglers about the tagged fish and what to do.

“When I heard about it, I said, ‘The information you glean is only going to be as good as the public response you get,’” Roberts said. “If no one knows about it, you kinda get nothing.”

Those wires, called “floy tags,” on the trout have a plastic coating with tiny writing with a code for the particular trout and a phone number to call. When a fisherman catches the fish, they should quickly make note of the tag color and number – maybe by taking a photo - before releasing the fish.

Then they should call the information in or enter it on the TU webpage along with the date and where they caught the fish.

“Please remind people: don’t remove the tag,” Roberts said.

TU Outreach Coordinator Bill Pfeiffer created a website with a map of the Clark Fork basin and its tributaries. As each tag is reported, it’ll appear on the map so the information is almost real-time.

Knotek predicts a lot of reports will pop up this summer and into the fall. The tags stay on the fish for a while but eventually fall out and fish will die, so reports will likely tail off after about a year or so.

But once the Trout Unlimited map fills up with dots, what does it mean?

Pfeiffer said a lot of money has been spent trying to learn about threatened bull trout, but more needs to be learned about other species that are popular with fishermen.

Last year, people were surprised when NorthWestern Energy biologists tagged a rainbow trout at the Thompson Falls dam and it was caught two weeks later at the mouth of Rattlesnake Creek after traveling 80 miles.

Then during Uthe’s tagging work, another Thompson Falls tagged rainbow was caught two weeks later in a fish trap in the lower Blackfoot River after swimming about 120 miles.

“There are the reasons you do a project and then there are the things you’re going to learn that you didn’t know you didn’t know,” Roberts said. “These efforts weren’t even coordinated. But because these tags were out there, we now know there’s connectivity from the Idaho border all the way into the Blackfoot River.”

While the trout are fun to catch in the larger rivers in the summer, they depend on the cold, clear water of tributaries to spawn. So the study could show how important even the small streams around Missoula are to the fisheries in the Blackfoot and Clark Fork rivers. The environment surrounding those streams needs to be conserved, especially as the climate warms, if trout are to thrive.

“We want people to understand why our restoration work in the tributary streams is important. The reason we’re putting fish screens on every ditch is because we want more fish in the main river,” Pfeiffer said. “A lot of the public doesn’t understand the fish they catch on the Clark Fork in the summer are in tributaries in the spring.”

Pfeiffer is using social media to get the word out to anglers and guides. They were going to do a big announcement at the April Westslope Trout Unlimited meeting but the COVID-19 shutdown put the kibosh on that. But Pfeiffer thinks that people will be interested in participating once they learn about it.

“Duck hunters are always trying to find banded ducks and we’re really trying to play off that,” Pfeiffer said. “I’m excited to go looking for them. I fish the Clark Fork every evening in the summer. I know sooner or later, I’m going to catch one.”