Fish Kill Event - Swan Lake

Carroll

Event ID: 1072
Date of Kill: 8/25/2025
Waterbody Type: Lake
Cause Origin: Natural
Cause: Environmental
Mode: N/A
Magnitude: 3 (1001 - 5000 fish killed)
County: Carroll
ESD Field Office: FO 4
Fisheries Office: Black Hawk Lake Office
LongDD: -94.84050
LatDD: 42.03654
Created Date: 5/15/2026 8:16:11 AM
Last Update: 5/15/2026 9:25:29 AM

For more information about this fish kill event, contact the Field Office or Fisheries Office listed above.

Impacted Assessment Segments

Lat/Long uses WGS84 datum

Onsite Comments

Thousands of dead fish were observed, with the vast majority being Bluegill. Yellow Bass were the next most common species found, followed by a smaller number of Black Crappie, Largemouth Bass, and Catfish. Weather data indicates a period of extremely high temperature followed by high winds and cooling temperatures about a week ago, likely disrupting thermal stratification and leading to low dissolved oxygen throughout the water column. According to CCB staff, dead fish were first observed over the weekend, beginning on or about Saturday (Aug 23). This timing aligns with the expected delayed effects of an oxygen sag and stress experienced around August 18–20.