Mouse Creek flows into a Sauk River slough at river mile 1.8 of the slough, and 18.6 of the river. This project, was completed in 1998 and involved lowering a culvert and placing three weirs (one rock and two log) downstream for grade control in order to restore 100 feet (30 m) of stream channel. These improvements opened up about 1400 feet (427 m) of spawning habitat. Three-hundred feet (91 m) of riparian zone including some mixed mature forest was planted with native trees and shrubs (part of the total 617 plants used on Powderhouse Creek). Mouse Creek is a WDFW index stream and is predominately utilized by coho, steelhead, and cutthroat trout.

In 1998-99, the winter after project completion, 128 live coho, 56 coho carcasses, and 18 coho redds were recorded. In 1999-00, coho numbers dropped to 86 live and 9 carcasses, though the number of redds increased to 41. In 2000-01, coho numbers dropped again to 30 live, 8 carcasses, and 15 redds. However, in 2001-02, 224live coho, 65 coho carcasses, and 53 coho redds were recorded. Four steelhead redds, and four live cutthroat trout were also observed in the spring of 2002. Like the winter of 2001-02, 224 live coho, 26 coho carcasses, and 117 coho redds were recorded during the winter of 2002-03. In 2003-04 Mouse Creek had totals with 330 live coho, 55 coho carcasses, and 86 coho redds. Five live cutthroat and one cutthroat carcass were observed. In 2004-05 Mouse Creek had its highest coho totals ever recorded by SFEG with 373 live, 119 carcasses, and 221 redds. During the 2005-06 season 124 live coho, 2 coho carcasses, and 48 coho redds were observed in Mouse Creek.