Late Winter Distribution of Stonecats in the Missouri and Lower Sun Rivers, Upstream of Great Falls, Montana

Abstract

Although stonecats (Noturos flavus) are native to the Missouri and Yellowstone river drainages in Montana, little is known about their distribution or population characteristics. Stonecats were first collected in the Missouri River near Craig, Montana in 1892. However. during extensive annual electrofishing surveys over the past 25 years m the same area, no stonecats had been collected. Hoop nets and cod traps were fished m the Missour River during March 2005 and 2006, and slat traps were fished during March 2006 to target smaller fish. Stonecats were only collected in the most downstream 19 km of the Missour River study reach. No stonecats were collected in cod traps. In 2005, mean hoop net catch rates were 2.8 stonecats/2-night period in the most downstream 19-km reach of the Missouri River, and no stonecats were collected m the 2006 Missouri River hoop nets. Slat trap catch rates m the 19-km reach of the Missour River were 0.2 stonecats/2-night period in 2006. In 2006, hoop nets and slat traps were hfished in the Sun River. Mean hoop net and slat trap catch rates in the Sun River were 4.8 and 6.5 stonecats/2-night period, respectively. Our results indicate that stonecats may be limited to the lower 1.9 km of the Missouri River (> 120-km downstream from the 1892 collection). We hypothesize that stonecat distribution has changed due to the cumulative effect of upstream reservoirs (Canyon Ferry, Hauser, and Holter) on the downstream water temperature regimens.