Fish Kill Event - Red Rock Reservoir
Elk Rock State Park, Boat Ramp area
- Event ID
- 1058
- Date of Kill
- 8/12/2024
- Waterbody Type
- Lake
- Cause Origin
- Natural
- Cause
- Disease/Parasite/Stress
- Mode
- N/A
- Magnitude
- 3 (1001 - 5000 fish killed)
- Estimated Fish Killed
- 150
- County
- Marion
- ESD Field Office
- FO 5
- Fisheries Office
- Boone Research Station
- LongDD
- -93.06071
- LatDD
- 41.40216
- Created Date
- 8/14/2024 8:20:14 AM
- Last Update
- 8/23/2024 8:14:02 AM
Reports of dead catfish along west shore of lake, near boat ramp at Elk Rock State Park. Approx 150 dead fish over 100 yards of shoreline. Fish from recently dead to about 48 hours. Some fish, but not all, seemed to have a bruise or hemorrhage behind the gills. Lots of water has been let out of the reservoir, but that slowed down dramatically in recent days. Fish ranged from age-1 to approximately age-6 (~24").
Environmental Conditions
Red Rock Lake experienced a change in environmental conditions early/mid-August. The USACE was in the process of returning the pool to normal elevation, and unseasonably cool air temperatures reduced water temperature.
Fish Kill
Dead Channel catfish along the west shoreline of Red Rock Lake were reported to Fisheries staff on 8/13/24. Mark Richardson (Large Impoundment Research) inspected the lake and discovered that a significant, species-specific fish kill had occurred. Richardson estimated that there were 150 dead fish/100 yards within the Elk Rock State Park shoreline, and that the fish had recently perished approximately 48 hours prior to his inspection. Richardson noticed bruising/hemorrhaging behind the gills. He estimated the dead fish to be 1-6 years old, and they ranged from 8-24”. An angler indicated to Richardson that he observed parasites on a few Channel catfish that he caught several days prior.
Boone Fisheries Management staff followed up with a second inspection of the lake on 8/14/24. The fish kill impacted most, if not the entire lake basin, resulting in well over 1,000 (possibly thousands) dead catfish. Staff attempted to collect struggling fish that could be submitted to the Minnesota DNR Fish Health Lab for pathogenic analysis, but the search was unsuccessful. The level of decomposition suggested that the fish had been deceased for at least 24 hours, likely longer. No other species appeared to have been impacted. Perfectly round holes/lesions were present on 50-75% of the dead fish during the visual inspection.
Cause of Death
Photos of the lesions were submitted to the MN DNR Fish Health Lab staff, but the cause of death was inconclusive. We speculate that the reduction in water temperature could have increased the susceptibility of Channel catfish to parasitic and subsequent bacterial infection, that ultimately led to death.