West Branch Floyd River IA 06-FLO-1558

Assessment Comments

Assessment is based on occurrence of a fish kill in July 1998 and 2001 Biocriteria sampling: Fish IBI= 22(poor), BM-IBI= 62(good).

Basis for Assessment

The assessment was based on the 1998 fish kill event (see 2000 assessment comments) and data collected in 2001 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).   The 2001 Fish IBI score was 22 (poor) and the BM-IBI score was 62 (good).  The aquatic life use support was assessed as partially supporting (=PS), based on a comparison of the F-IBI and BM-IBI scores with biological assessment criteria established specifically for the 2002 Section 305(b) report.  The biological assessment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2001.