Assessment Comments
Assessment remains based on results of a fish kill investigation in 2004.
Basis for Assessment
SUMMARY: The Class B(LW) aquatic life uses of this waterbody remain assessed (evaluated) as “partially supported” due to a fish kill in March 2004. The kill was attributed to natural causes. This impairment is appropriate for Category 3b of Iowa’s 2010 Integrated Report. The Class C (drinking water) remain "not assessed" due to the lack of recent information upon which to base an assessment. The data used for previous assessments of the Class C uses of this lake are now considered too old (10 years) to accurately characterize current water quality conditions. Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring at this lake. This is the same assessment as that developed for previous assessment/listing cycles.
EXPLANATION: The Class B(LW) uses remain assessed (evaluated) as "partially supported" due to a fish kill in March 2004. This kill occurred on or before March 1, 2004; the kill was attributed to natural causes (winterkill). An estimated 500 fish (gizzard shad) were killed; all fish were approximately 8 to 9 inches in length. No estimate of the value of the fish killed was provided. This is the same assessment as that developed for previous assessment/listing cycles. The continuance of the IR Category 3b listing is based on IDNR's assessment methodology that states the following: the occurrence of a single pollutant-caused fish kill, or a fish kill of unknown origin, on a waterbody or waterbody reach during the most recent assessment period indicates a severe stress to the aquatic community and suggests that the aquatic life uses should be assessed as “impaired”. If a cause of the kill was not identified during the IDNR investigation, or if the kill was attributed to non-pollutant causes (e.g., winterkill), the assessment type will be considered “evaluated” and will be placed in IR subcategories 2b or 3b and will be added to the state list of waters in need of further investigation. Thus, this assessment segment will remain in Category 3b of Iowa’s Integrated Report. Kills of gizzard shad due to cold water temperatures in winter are common in Iowa lakes and rivers; these kills are typically not related to pollutants or degraded water quality conditions. Thus, this kill alone, does not indicate an impaired condition of Lake Fisher's Class B(LW) uses. The presence of gizzard shad in this lake, however, potentially suggests more significant problems for support of the Class B(LW) uses than does a winterkill of this species.
Note: this lake is not part of the ongoing statewide survey of 132 Iowa lakes conducted by Iowa State University and the University of Iowa Hygienic Laboratory (UHL).
The Class C (drinking water) uses remain "not assessed" due to the lack of information upon which to base an assessment. The previous assessments of the Class C uses at this lake were based on results of sampling conducted by UHL in January 1995. However, because these data are now considered too old (greater than ten years) to accurately characterize current water quality conditions, these uses are now considered "not assessed".
Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring at this lake.
