Missouri River Brown Trout Estimates Complete

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Missouri River Brown TroutBrown trout populations on the Missouri River between Holter Dam and the town of Cascade are up, say state fisheries biologists.

Fish, Wildlife and Parks fisheries crews recently completed the annual population estimates for brown trout in the 33-mile stretch of the Missouri River.

This year the number of brown trout greater than 10 inches in the section near the town of Craig section was estimated at 1,126 per mile, more than twice as much as the 22-year average of 554, says Grant Grisak, Fish, Wildlife and Parks fisheries biologist.

In the Pelican Point section, just upstream of Cascade, biologists estimated the number of brown trout greater than 10 inches to be 490 per mile, also greater than the long-term average of 340, Grisak says.

“The Craig estimate was the fourth highest on record and is due to an abundance of fish between 13 and 19 inches long,” Grisak says. “Nearly 75% of the brown trout in this section of river are within this length range. The Pelican Point estimate was the fifth highest on record and is due to a slightly higher number of fish in the 15-18 inch range.”

Brown trout population estimates are conducted each spring when most rainbows are in the tributaries spawning. The fisheries crew capture brown trout by electro-fishing, mark them, and try to recapture them two weeks later. By analyzing the proportion of marked to unmarked fish, biologists are able to calculate an estimate of the trout population.

This year, Grisak added, “We’ve been fielding a lot of questions about the recent rain and high water conditions. This is something we have not been accustomed to over the past nine years, but these conditions are actually closer to normal than most can remember from recent history.”

The high water from above average snow pack and rainfall should not affect fish eggs in spawning tributaries.