Spawning study finds bull trout are stable

Recently completed bull-trout spawning surveys in the North and Middle Fork Flathead river drainages indicate there is a stable population, according to state biologists.

This year’s surveys were a comprehensive, basinwide effort that focused on all of the known spawning streams in the North and Middle Fork drainages. The basinwide surveys, carried out every few years, were conducted on 31 streams, including the eight “index” streams that are surveyed every year in the North and Middle Fork drainages.

Montana Fish, Wildlife and Parks biologist Tom Weaver said the basinwide surveys are basically a way of testing whether the annual index surveys accurately reflect bull trout reproduction trends.

The index counts have accounted for about 45 percent of the basinwide counts over time, and that was again the case this year, Weaver said.

“The index counts adequately describe what is going on basinwide, and the trend is stable,” said Weaver, who has led the surveys of bull trout spawning beds, called redds, for the last 33 years.

This year, there were 220 redds counted in the North Fork compared to 250 in 2008, when the last basinwide count was conducted. There were 280 redds counted in the Middle Fork compared to 253 in 2008. The total is 500 compared to 503 in 2008.

The North Fork count includes six spawning streams that are in Canada. The Middle Fork survey includes 10 streams that are in the Great Bear Wilderness.

The North Fork’s Coal Creek has been one of the most troubled spawning streams over the last 30 years, dropping from a high count of 61 redds in 1983 to several years over the last decade with zero redds. This year’s count of 11 redds was nearly double last year’s count of six.

Biologist Mark Deleray noted there were strong redd counts in several Middle Fork spawning streams. The 171 redds counted in the four index streams alone easily exceeded last year’s count of 124.

Field crews still are conducting surveys in the South Fork Flathead drainage and the Swan River drainage. Those surveys should be finished in the next week, said Deleray, who noted that this year’s survey conditions have been excellent. 

“There’s low flows, clear water and bright redds,” he said.

Reporter Jim Mann may be reached at 758-4407 or by email at jmann@dailyinterlake.com.