Johnson Creek IA 02-CED-559

Assessment Comments

Assessment is based on results of IDNR/UHL biological (REMAP) monitoring in 2002: Fish IBI= 54 (good), BM-IBI= 56 (good).

Basis for Assessment

SUMMARY:  The general aquatic life uses are assessed (evaluated) as "fully supported / threatened" (minor impacts) based on results of IDNR/UHL biological (REMAP) sampling in 2002.   The assessment type is considered "evaluated" (relatively lower confidence assessment) due to the uncertainty of using biological assessment methods developed for Class B(LR) and wadable Class B(WW) streams for assessing aquatic life conditions in general use-only stream segments.

EXPLANATION:  The assessment of the general aquatic life uses was based on data collected in 2002 as part of the IDNR/UHL REMAP 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 2002 Fish IBI score was 54 (good) and the BM-IBI score was 56 (good).  The aquatic life use support was assessed as fully supporting/threatened (=FS/T), based on a comparison of the F-IBI and BM-IBI scores with biological assessment criteria established for previous Section 305(b) reports.  The biological assessment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2001.