Big Creek restoration efforts pay off for bull trout

After decades of restoration efforts, one of the main tributaries of the North Fork of the Flathead will be removed from the state’s list of sediment-impaired waters.

Big Creek was once a prime bull trout-spawning stream, but logging operations that decades ago came right to the water’s edge left the stream impaired by fine sediment and silt from the resulting erosion.

The Montana Department of Environmental Quality and Flathead National Forest’s Glacier/View Hungry Horse Ranger District made the announcement earlier this month.

All told, 60.6 miles of dirt roads in the drainage have been decommissioned, and 47 culverts have been removed, Flathead National Forest aquatics program manager Craig Kendall said last week. In addition, 89 miles of roads have been improved to much higher standards, and 19 culverts have been replaced with larger culverts designed to withstand 100-year floods, Kendall said.

Culverts can be a main source of sediment loading in a stream, particularly if they plug up, causing road erosion. Roads, particularly those that are improperly built, can also erode and cause sediment problems in streams.

Native bull trout migrate from Flathead Lake to spawn in the tributaries of the North and Middle Forks of the Flathead. Fish biologists count redds, or spawning beds, to get an idea of how the adult bull trout population is doing.

In the 1990s, fish biologists recorded a sharp decline in the number of redds in Big Creek, with a low of just six redds in 1996. The numbers rebounded somewhat in the last 10 years, with a high of 40 redds in 2007. Just nine redds were recorded last year, but that was likely due to high water obliterating some of the beds.

DEQ added Big Creek to Montana’s list of waters with impaired water quality in 1996, and the Flathead Forest collaborated with DEQ to complete a watershed restoration plan in 2003. The plan prescribed a variety of best management practices for reducing sediment loads from controllable sources in the watershed.

Recent monitoring data shows that sediment and stream conditions in Big Creek are now similar to conditions in streams with minimal human impacts. Most notably, there has been a substantial decrease in the amount of sand and silt in bull trout spawning habitat.

Based on this data, DEQ removed sediment as a cause of impairment to Big Creek, and the Environmental Protection Agency approved the action in April.

But while the water quality is much improved, the future of bull trout remains in doubt, noted Pat VanEimeren, a fisheries biologist for the Flathead National Forest.

Bull trout are still threatened by predatory non-native lake trout in Flathead Lake. The fear is that lake trout will eventually completely take over the watershed, and bull trout will go all but extinct in the drainage.

Climate change could also play an important role in the long-term future of bull trout. Models suggest the area’s waters could get warmer, which is fatal to bull trout because it has less dissolved oxygen.

There is the possibility that bull trout could evolve over time and become a fluvial fish — living primarily in rivers and streams. Bull trout in other parts of the state, including the St. Mary River drainage, are primarily river-dwelling fish. Lake trout are a native species in that drainage.

But that type of evolution could take hundreds of years, and the historic runs of bull trout in the North Fork, where as many as 400 redds were counted basinwide in the 1980s, will likely never happen again.