Bull trout numbers average except in the Swan

Montana Fish, Wildlife and Parks biologists recently completed counts of bull trout redds (nests) in the eight standard stream index sections for the Flathead Lake population.

Bull trout spawn in the fall and build nests in tributaries during September and October. These counts serve as an index of how many migratory adult bull trout successfully spawn.

Crews also conducted surveys for fish populations for the Hungry Horse Reservoir and South Fork of the Flathead drainage and the Swan River drainage. The same stream sections are surveyed annually and represent a known portion of the total bull trout spawning runs in each drainage.

The Flathead count is an index of spawners migrating upstream from Flathead Lake. The partial count for the eight Middle and North Fork tributaries combined was 189 redds, which is average for the past decade. 

The South Fork total basin-wide count was 610 redds, which is well above average. This count reflects bull trout migrating upstream from Hungry Horse Reservoir and includes reservoir tributaries and upper South Fork tributaries. 

The Swan drainage bull trout redd count was 312 redds, which is 52 percent below average. This count reflects bull trout migrating upstream from Swan Lake.

The decline in bull trout redds in the Swan drainage over the past several years has led biologists to suggest a change in angling regulations. Swan Lake has been managed with a one bull trout per day fishing regulation, and annual harvest has averaged about 180 bull trout. A shift to catch-and-release regulations with no harvest was approved by the Fish, Wildlife and Parks Commission at their meeting on Nov. 10.