Assessment Comments

Three pollution-caused fish kills: 1985, 1989, and 1996. Biocriteria sampling site in Linn County.

Basis for Assessment

Added biocriteria sampling results from one location in Linn Co.  sampled in Aug.  1996.  The site is upstream several miles from area of repeated fish kills.  Fish sampling results indicate good fish community health (IBI=54, max.  poss.  score=60).  Game fish and several intolerant fish species were present.  Habitat quality was evaluated as fairly good.  Stream is relatively wide and shallow, with occasional riffles.  Pasture impacts are evident in some reaches.  The relatively high quality fish community suggests good water quality.  Livestock feedlots and streamside pasture use are threats to continued attainment of B(WW) aquatic life use.   A review of the results of the August 1996 DNR biocriteria sampling in Linn County, upon which this assessment is based, shows that, in the absence of impacts to the physical characteristics of this stream, full support of the Class B(WW) aquatic life uses would be indicated due to (1) presence of an exceptionally diverse fish community (31 species from 6 families) for streams in the Iowan Surface subecoregion (47c), (2) presence of all the expected fish taxa (11 of 11) for streams in this subregion, (3) presence of game fish species, including channel catfish (1) and smallmouth bass (49), and (4) presence of several envrionmentally sensitive species, including American brook lamprey, rosyface shiner, northern hogsucker, rock bass, smallmouth bass, and four darter species including banded darter (25).