Ladd Knotek is disturbed by the lack of attention being paid to the many western Montana streams where bull trout populations are struggling to survive.
The fisheries biologist with Montana Fish, Wildlife and Parks knows people love to latch on to the success stories from streams like Fish Creek and several Blackfoot tributaries, where bull trout populations are viable.
“But what nobody talks about is all these other populations that, 50 years ago, these were all viable populations,” he said Tuesday as part of a presentation on bull trout in Rattlesnake Creek. “You know, Gold Creek, Belmont Creek, Trout Creek, there’s a whole list of them. There’s a whole bunch of them that are just basically on the verge of disappearing. And what we like to talk about are the ones that are doing OK. But in places like Lolo Creek and some Bitterroot tributaries, bull trout there are just barely hanging on.”
Bull trout have faced a long, slow decline over the past century, to the point where they are now listed as a threatened species under the Endangered Species Act. Success is a relative term even in the places where they are doing well.
“They’re nowhere near what they were historically,” Knotek said of the tributaries where the populations are relatively healthy. “But they have a fair number of adult spawners coming in. People see them in the fishery. But we need to start looking at all these other tributaries that used to be bull trout spawning tributaries and recognize what’s going on in the bigger picture. We’re just looking at a very thin slice instead of looking at the whole thing. A lot of this stuff is just symptoms of what’s going on at the larger scale. Bull trout are the canary. They’re very susceptible to environmental change, whether it’s temperature, whether it’s physical, whether it’s sediment. There’s something going on in these drainages and the symptoms we’re seeing are the bull trout distribution is shrinking, we’re losing populations and we’re seeing expansion of nonnatives.”
Bull trout – which are native to the Columbia River Basin and are only found west of the Continental Divide in Montana – need clear, cold mountain waters to spawn and require clean gravel beds, deep pools, complex cover, good in-stream flows in the fall and large systems of interconnected waterways for their migrations. Rising temperatures and falling water levels trigger their migration to spawning tributaries in June, and they hang out until they spawn in the fall. They are much more susceptible to warming temperatures and habitat change than nonnative species such as brown and rainbow trout.
Knotek was the featured presenter Friday for a discussion on restoration efforts and the importance of Rattlesnake Creek as a bull trout habitat. The event was organized by the Clark Fork Coalition, a nonprofit in Missoula that aims to protect water quality for the 22,000-square-mile Clark Fork River Basin.
Knotek explained that because Rattlesnake Creek is south-facing and doesn’t have much groundwater recharging, it has much less of a buffer against a warming climate than other streams.
“The water temperatures are significantly higher than they were 10 years ago,” he said. “The types of temperatures we’re seeing in late summer and early fall, we never saw those 10 to 15 years ago. Water temperature is driving a lot of what we’re talking about. It’s definitely stressful on fish. It doesn’t spell good news for bull trout.”
Knotek said it’s a common misconception that brown trout and rainbows are driving out bull trout, and he explained that those nonnative species are simply moving in because the native species is dying off.
“It’s replacement rather than displacement,” he said.
In Rattlesnake Creek, biologists have conducted redd counts of the migratory population in the lower reaches since 1999. There is a healthy resident population in the upper reaches, but researchers are more interested in the fish that actually migrate to the Clark Fork River.
The results have been disturbing.
They found a high of 36 in 2006 and 24 in 2008, before Milltown Dam was removed. There was an expected drop to just four redds – spawning beds – after the dam was removed in 2009, because of the massive disturbance. However, the number of redds has not bounced back since, and researchers found just six last year.
“That tells us that it wasn’t just the dam removal that caused it, because they should be recovering by now,” Knotek said. “And there are lots of populations like this stream that are not doing well but need more attention. We’ve got a problem here, but it’s not inconsistent with other tributaries. There’s something bigger going on.”
Knotek said that Rattlesnake Creek was historically braided before the area was developed, and that eliminated a lot of the back channels the juvenile fish need to grow.
“You need complexity,” he said. “When you have a straight ditch in a system that used to be braided, it ain’t good.”
He’s also seen much more algae growth in the upper sections, something that is obviously related to higher temperatures and added nutrients.
“We have browns and rainbows progressing upstream, and we attribute that to water temperature,” he said. “That’s consistent with other streams, too. It’s very obvious something is going on here.”
Knotek believes that a “ramping up” of current conservation work is the only thing that can save bull trout populations. Fish screens, the removal of dams, awareness of anglers and water conservation – especially by people using stream irrigation to water their lawns – is crucial.
“Bull trout are the canary,” he said. “But there are a lot of other species that we could be looking at as indicators as well. A lot of research needs to be done. There’s a lot of species being affected.”