Flathead bull trout numbers appear stable
Long-term bull trout numbers appear to have stabilized in the Flathead River drainage, according to bull trout redd surveys completed this fall by Montana Fish, Wildlife and Parks biologists.
A redd is a bull trout spawning bed that’s excavated in the gravel of a stream. Biologists wade the streams in the fall and count the number of redds, which gives them an idea of how well the fish population is doing.
This year, biologists sampled basinwide tributaries in the North and Middle forks of the Flathead. In the North Fork, they counted 220 redds, which is slightly lower than the basinwide count in 2008, where 250 redds were counted. But it’s much more than in 2003, when only 165 redds were counted.
In the Middle Fork, the basinwide count was 500, compared to 503 in the 2008 and 297 in 2003. It’s important to note that 2003 was a fire year and the area experienced a severe drought.
While the numbers are holding their own, they pale in comparison to the 1980s. In 1982, for example, 768 redds were counted basinwide in the North Fork, and 1,156 were counted in the Middle Fork. Still, this year’s numbers are encouraging, FWP fisheries biologist Tom Weaver said.
“We’re a heck of a lot better than 1992 through 1997,” he said.
In 1997, for example, the basinwide count was 98 redds in the North Fork and 236 in the Middle Fork.
Weaver surmised some sort of biological equilibrium may have been reached in Flathead Lake. Over the past 30 years, non-native lake trout bloomed in Flathead Lake, to the demise of native bull trout. Lake trout have an advantage over bull trout because they spawn in the lake, whereas bull trout migrate up tributaries to spawn.
The migration can be tough on the fish, exposing them to predators and anglers. In the North Fork, bull trout poaching has been a problem, and even when they’re released by anglers, a handled fish can be exposed to fungal infections, he said. Weaver also thinks biological studies in the region could also have an impact — researchers can also expose the fish to fungal infections.
The North Fork also has habitat problems caused by logging practices decades ago. Today, better land management and logging techniques are being used, but it can take decades for a fishery to recover.
“The North Fork in general is a concern,” Weaver said.
The Middle Fork probably has better numbers because it sees less angling pressure, but the habitat could also be better. Most of the drainage has seen little human development — it’s either in Glacier National Park or the Great Bear Wilderness.
The top spawning stream in the Middle Fork, Morrison Creek, mostly lies within the wilderness. Ole Creek, another excellent spawning stream, is located inside Glacier Park. Bull trout are wholly protected in both drainages, and fishing for them is illegal.
Weaver said he doesn’t think a proposed gill-netting project on south end of Flathead Lake would benefit the bull trout fishery. He’s worried that with larger lake trout removed by nets, the end result could be higher numbers of smaller lake trout in the 14- to 15-inch category that are still predatory on young bull trout.