East Branch West Nishnabotna River IA 05-NSH-1823

Assessment Comments

1994 Biocriteria.

Basis for Assessment

The assessment was based on data collected in 1994 approximately 4.5 miles northeast of Avoca as part of the DNR/UHL stream biocriteria project.   A series of biological metrics which reflect stream water quality and habitat integrity were calculated from the biocriteria sampling data.   The biological metrics are based on the numbers and types of benthic macroinvertebrate taxa and fish species that were collected in the stream sampling reach.   The biological metrics were combined to make a fish community index of biotic integrity (F-IBI) and a benthic macroinvertebrate index (BM-IBI).   The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum).

Only the Fish-IBI was calculated for this assessment.   The F-IBI score was 39 (fair).   The aquatic life use support was assessed as fully supported / threatened (=FST), based on a comparison of the F-IBI score with biological assessment criteria established specifically for the 2000 Section 305(b) report.   The biological assessment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-1998.