Assessment Comments
Assessment based on 2000 biocriteria data: Fish IBI = 21 (poor), BM-IBI= 32 (fair) and on 1999 Fisheries data: Fish IBI = 33 (fair).
Basis for Assessment
SUMMARY: The Class B(LR) aquatic life uses remain assessed as "partially supported" based on results of biological monitoring in 1999 and 2000. The full biological monitoring in 2000 suggests "not supporting" while the evaluated assessment of the 1999 data suggests "fully supported/threatened". Because of the segment's proximity to the upstream marsh, and the marsh-like qualities of the year 2000 site, it was determined to loosely apply the biological criteria and enter this assessment as evaluated. According to IDNR's assessment methodology, "evaluted" impairments are of relatively lower confidence that “monitored" which have relatively higher confidence. Such "evaluated" waters, while not appropriate for addition to Category 5 of the Integrated Report (= Section 303(d) list), will be placed in either Category 2b or 3b of the IR and thus will be added to the state’s list of “waters in need of further investigation”.
The assessment was based on data collected in 2000 as part of the DNR/UHL stream biocriteria project and on 1999 Manchester Fisheries stream sampling data. 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 2000 Fish IBI score was 21 (poor) and the BM-IBI score was 32 (fair). The 1999 Fisheries Fish IBI score was 33 (fair). 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 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.
