FWP biologists are optimistic about bull trout redd report

Bull trout spawning surveys in eight North and Middle Fork Flathead River tributaries have been completed by Montanta Fish, Wildlife & Parks officials ,  and the results are encouraging.  

Biologists count the number of redds or nests built in streambed gravels by adult bull trout from Flathead Lake. Identical sections are counted annually and represent a known portion (about 45 percent) of the total bull trout spawning in the drainage. The entire drainage is counted every three to five years.

This is the best estimate of the mature bull trout spawning run from Flathead Lake.

This year’s basinwide estimate of 500 redds indicates a stable bull trout population as reflected by the number of successfully spawning adult bull trout migrating upstream from Flathead Lake.  

The counts have been relatively stable during the past 15 years (about 3 generations of bull trout), averaging 434 redds. This year’s estimate of 500 redds is 66 percent above the minimum secure level of 300 redds calculated for the Flathead Lake bull trout population under the Flathead Lake and River Fisheries Co-Management Plan.

Based on the average number of eggs per female, this translates to several million eggs deposited in the gravels of North and Middle Fork Flathead tributaries.

Mature bull trout migrate upstream from Flathead Lake in the summer, spawn in September, and then return to Flathead Lake in October after spawning.  The young fish hatch and then live in the tributaries from one to three years before migrating downstream to Flathead Lake to grow to adults and complete the life cycle.

Biologists estimate that about half the adult bull trout in Flathead Lake spawn each year.

(This report was based soley on a press release from Montana Fish, Wildlife & Parks.)