Middle Raccoon River IA 04-RAC-1191

Assessment Comments

Assessment remains based on: (1) fish surveys by the IDNR Fisheries Management Section from 2007-2010 and surveys by the IDNR Fisheries Research Section and (2) results of U.S. EPA/IDNR fish tissue (RAFT) monitoring in 2007.

Basis for Assessment

SUMMARY:  The Class A1 (primary contact recreation) uses remain "not assessed” (IR 3a) due to lack of information upon which to base an assessment.   The Class B(WW1) aquatic life uses remain assessed (evaluated) as "fully supported" (IR 2a) based on results of fish surveys conducted by (1) the IDNR Fisheries Management Section (Cold Springs) from 2007-10 and (2) the IDNR Fisheries Research Section in 2002.   Fish consumption uses are assessed (monitored) as "fully supported"  (IR 2a) based on results of U.S.  EPA/IDNR fish tissue monitoring in 2007.  

EXPLANATION:  The Class A1 (primary contact recreation) uses remain "not assessed" due to the lack of water quality information for this segment upon which to base an assessment.  

The Class B(WW1) aquatic life uses remain assessed (evaluated) as “fully supporting” partially based on data collected in 2002 as part of an IDNR Fisheries stream sampling project: Manchester research station.   A series of biological metrics which reflect stream water quality and habitat integrity were calculated from the Fisheries sampling data.   The biological metrics are based on the numbers and types of 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).   The index ranks the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum).   The 2002 evaluated FIBI was 44 (fair).   The aquatic life use support was assessed (evaluated) as fully supporting (=FS), based on a comparison of the FIBI score with biological impairment criteria (BIC) established for previous Section 305(b) reports.   The biological impairment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2004.   The FIBI BIC for this ecoregion is 36 and this segment passed the FIBI BIC 1/1 times in 2002.  

This aquatic life assessment is now considered "evaluated" based on a change in the 2010 IDNR assessment methodology.   IDNR now requires a segment have two or more biological samples collected from the segment in multiple years over a five-year period to be considered “monitored”.   This segment had a single sample collected in 2002.   Additionally, because these data are now considered too old (greater than five years) to accurately characterize current water quality conditions, the assessment category is considered “evaluated” (indicating an assessment with relatively lower confidence) as opposed to "monitored" (indicating an assessment with relatively higher confidence).   Despite this change in assessment methodology and type, this waterbody remains in IR Category 2a.  

The assessment of aquatic life uses (fully supported) is also based on results of IDNR Fisheries Bureau surveys to determine the status of the smallmouth bass population in this river segment.   Previous assessments of aquatic life use support for this segment have included information from the IDNR Fisheries Bureau indicating problems with growth and reproduction of smallmouth bass.   Both habitat quality and water quality (high levels of ammonia-nitrogen) were seen as potentially impacting the smallmouth bass populations in this segment.   Updated (2010) information from the IDNR Fisheries Bureau (Hayes), however, suggests an improvement in the smallmouth bass population of this river segment.   Variability in annual reproductive success among the smallmouth bass leads to wide fluctuations in the Middle Raccoon River population; this pattern of variation in year-class strength is present in other Iowa rivers supporting smallmouth bass populations.   Habitat degradation and other environmental factors (high discharges during floods) are the most likely cause of the inconsistent year class success among the smallmouth bass.   IDNR's 2009 fishery survey showed significant improvements in the population with fish present from 5 different age groups (year classes) and strong numbers of smallmouth bass from the 2008 and 2007 year classes.   Fish ranged from 3 ½ inches to 17 inches in the sample.   Habitat quality remains to be a concern and a limiting factor.   IDNR Fisheries Research is conducting habitat surveys in order to compare habitat conditions today to those measured during previous surveys.   Fish from the 2008 and 2007 year class will drive the fishery over the next few years.   The most recent fishery survey indicates that the smallmouth bass failed to pull off a year class in either 2010 or 2009.   The population will continue to fluctuate as a result.   IDNR Fisheries is not aware of the problems with high levels of ammonia in this river reach.   The wastewater treatment facility for the city of Panorama has installed a diffuser pipe in the river to more evenly distribute and efficiently dilute effluent discharged.  

Fish consumption uses remain assessed (monitored) as “fully supported” based on results of U.S.  EPA/IDNR fish contaminant (RAFT) monitoring at the Middle Raccoon River southeast of Panora in 2007.   The composite samples of fillets from common carp and smallmouth bass had low levels of contaminants.   Levels of primary contaminants in the composite sample of common carp fillets were as follows: mercury: 0.097 ppm; total PCBs: 0.099 ppm; and technical chlordane: <0.03 ppm.   Levels of primary contaminants in the composite sample of smallmouth bass fillets were as follows: mercury: 0.0554 ppm.   The existence of, or potential for, a fish consumption advisory is the basis for Section 305(b) assessments of the degree to which Iowa’s lakes and rivers support their fish consumption uses.   The fish contaminant data generated from the 2007 RAFT sampling conducted at this river show that the levels of contaminants do not exceed any of the advisory trigger levels, thus indicating no justification for issuance of a consumption advisory for this waterbody.