Middle Raccoon River IA 04-RAC-1191

Assessment Comments

Assessment is based on surveys by the DNR Fisheries Bureau (the most recent in September 2000).

Basis for Assessment

SUMMARY:  The Class A (primary contact recreation) uses remain "not assessed."  The Class B(WW) aquatic life uses remain "fully supported / threatened."  Fish consumption uses remain "not assessed."  EXPLANATION:  The Class A uses remain "not assessed" due to the lack of monitoring for indicator bacteria in this reach of river.   The Class B(WW) uses remain assessed as "fully supported / threatened" based on results of recent (September 2000) surveys by the DNR Fisheries Bureau that continue to show problems with smallmouth bass populations in this river reach (see assessment developed for the 1998 report above).   According to the DNR Fisheries Bureau, the leading hypothesis for explaining the lower numbers of smallmouth bass is that prolonged flooding in summer 1993 resulted in a wider and less well-defined channel, increased streambank erosion, slower moving water with less scouring action, and increased deposition of finer, softer substrate types (silt and sand).   All of these changes in the river suggest a decline in the quality of aquatic habitats for smallmouth bass.  While this river reach continues to support a warmwater fish community typical of central Iowa rivers, the numbers of smallmouth bass remain lower than during the late 1980s and early 1990s.   The DNR Fisheries Bureau continues to study this problem and has suggested that streambank stabilization measures (for example, jetties) may help increase streambank stability and improve aquatic habitats.   Fish consumption uses remain "not assessed" due to a lack of fish tissue monitoring in this river reach.