Johnson Creek IA 02-CED-559

Assessment Comments

Assessment is based on results of IDNR/UHL biological (REMAP) monitoring in 2002: FIBI = 54 (good), BMIBI = 54 (fair). Non-riffle site FIBI BIC = 44, articficial substrate BMIBI BIC = 52.

Basis for Assessment

SUMMARY:  The general aquatic life uses are assessed (evaluated) as "fully supported" 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 (FIBI) and a benthic macroinvertebrate index (BMIBI).   The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum).   The 2002 FIBI score was 54 (good) and the BMIBI score was 54 (fair).   The aquatic life use support was assessed as fully supporting (=FS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2004.   The non-riffle site FIBI BIC for this ecoregion is 44 and the artificial substrate BMIBI BIC for this ecoregion is 52.   Even though this site passed both the FIBI and BMIBI BICs, it is uncertain as to whether or not this segment is meeting the aquatic life criteria because it is a small general use stream and doesn’t fall in the calibrated watershed size.