Spawning surveys in Flathead show positive results for Bull Trout
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News from Montana Fish, Wildlife and Parks
FLATHEAD LAKE — Bull trout spawning surveys in eight North and Middle Fork Flathead River tributaries were completed by Fish, Wildlife and Parks between Oct. 1-10 and the results are encouraging.
Biologists count the number of “redds” or nests built in streambed gravels by adult bull trout from Flathead Lake. The entire drainage is counted every three to five years, and this is the best estimate of the mature bull trout spawning run from Flathead Lake.
This year’s basin-wide estimate of 500 redds indicates a stable bull trout population upstream from Flathead Lake. The counts have been relatively stable over the past 15 years (about three 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. Mature bull trout migrate upstream from Flathead Lake in the summer, and about half 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. .This year’s estimate of 500 redds is encouraging and indicates the current bull trout population is relatively stable. This was the 33rd consecutive year of index counts for the Flathead Lake bull trout population.
