Fish Kill Event - Nashua Impoundment - Cedar River
Nashua
- Event ID
- 1033
- Date of Kill
- 8/22/2021
- Waterbody Type
- Lake
- Cause Origin
- Natural
- Cause
- Environmental
- Mode
- N/A
- Magnitude
- 2 (101 - 1000 fish killed)
- Estimated Fish Killed
- 356
- County
- Chickasaw
- ESD Field Office
- FO 1
- Fisheries Office
- Decorah State Hatchery
- LongDD
- -92.54493
- LatDD
- 42.95825
- Created Date
- 10/7/2022 11:24:27 AM
- Last Update
- 10/7/2022 11:24:27 AM
Photographs and dissolved oxygen (DO) readings were made above and below the dam. Water visibility was less than a foot and brown. DO above the dam at 11:28 am read 1.44 ppm with a surface water temperature of 77.2° F. DO below the dam at 11:41am read 2.99 ppm with 77.5° F surface water temperature. Traveling up river to Midway CCB Park boat ramp no dead fish found with similar water conditions. Dissolved oxygen reading at 1:21 pm at the end of the dock at the boat ramp in City Park. DO at this time was 8.86 ppm with water temperature 76.6° F. Staff spoke with local folks about river conditions to discover the impoundment looked like pea soup prior to high water events around August 9 th indicating a severe algal bloom occurring due to extreme low water with an extended period of hot dry weather. Following this rain event, hot low oxygenated water mixed with cool oxygenated water causing the algae to die-off. This algal die-off and return to significantly low water levels further depleted the dissolved oxygen likely causing the fish kill.