Calmus Creek IA 02-WIN-845

Assessment Comments

Assessment based on October 1992 DNR stream use assessments in Cerro Gordo County, as well as fish survey data from the report "Calmus Creek Stream Survey Report, Mason City, Iowa, Holnam, Inc." prepared by GZA GeoEnvironmental, Inc.

Basis for Assessment

Used a review of the field sheets from the October 1992 DNR stream use assessments in Cerro Gordo County, as well as fish survey data from the report "Calmus Creek Stream Survey Report, Mason City, Iowa, Holnam, Inc." prepared by GZA GeoEnvironmental, Inc.  in October 1994 (Table 4) to downgrade the support of the Class B(LR) aquatic life uses from FST to PS due to  a general reduction in fish community diversity proceeding downstream as the stream receives effluents from local cement companies (i.e., from the 1994 Holnam study, species/families, upstream (above first outfall) to downstream:  9/4; 8/3; 4/2).   Similarly, the catch/effort drops from 160 fish/30 minutes of electrofishing above the outfalls to 55 fish and 70 fish/30 minutes downstream.  The number of expected fish taxa for Iowan Surface streams also shows this decline in a downstream direction:  8 of 11 above the outfalls, 5 of 11, and 4 of 11.   Although captured at the upstream site, no common shiners, Notropis spp., or sunfishes were captured at the two downstream sites; darters were not capatured at any of the 3 sites.   The results of the two DNR stream use assessment in 1992 are consistent with this pattern, with the upstream site having 7 of the 11 expected fish taxa, while the downstream site (in the vicinity of the outfalls) had only 4 of the 11 taxa present.   Although habitat differences between sites may account for some of the decrease in fish community diversity downstream, and while macroinvertebrate data may contradict results of fish sampling, sufficient evidence exists to conduct follow-up monitoring to better define the status of the aquatic communities of this stream.