Assessment Comments
1991 stream use assessment in Clayton county. Fish surveys at 7 locations as part of 1988 UHL survey.
Basis for Assessment
Subdivided the previous 34-mile Class B(LR) reach of Roberts Creek at Howard Creek to improve assessments. Used a review of the field sheet from the November 1991 DNR stream use assessment, as well as the results of fish surveys conducted for the 1988 UHL report "A Survey of The Benthic Macroinvertebrates and Fishes of the Big Spring Basin, Iowa" (UHL Report 88-9), to assess support of the Class B(LR) aquatic life uses as FST due to (1) presence of moderately to relatively diverse fish communities at the 7 sites sampled in this reach (species/families, dstr->upstr: 15/5; 15/4; 11/4; 9/3; 9/3; 9/3; 9/5), (2) presence of a majority of fish taxa expected for Class B(LR) strams in the Driftless Area ecoregion (52) at all sites, with nearly all the expected taxa at the two most downstream sites (dstr->upstr: 8 of 9 at the two downstream sites; 7 of 9 at the remaining 5 sites), and (3) indications of good habitat quality. Both the field sheet from the DNR stream use assessment and the UHL report mention pasturing of the riparian zone as a threat to the biological integrity of this stream. In addition, the UHL report notes stream channelization activities near the confluence with Deer Creek caused a decline in fish community diversity (see p. 18). Support of the Class B(LR) uses is also threatented by fish kills. The UHL report describes a fish kill on a tributary of this reach of Roberts Creek (Silver Creek), although no impacts of of the kill on Roberts Creek were observed (see page 21). A more recent kill occurred on Roberts Creek near the confluence with Silver Creek in August 1996; no cause or source of this kill was determined. Most of the data upon which this assessment is based are approximately 10 years old. Additional monitoring is needed to update this assessment and to determine the status of the aquatic communities and habitats of this stream.
