Iowa DNR
Iowa DNR Fish Kill Database

Fish Kill Event - Chariton River

immediate below Rathbun Dam

Event ID
952
Date of Kill
3/4/2018
Waterbody Type
River/Stream
Cause Origin
Anthropogenic
Cause
Gas Bubble Disease
Mode
N/A
Magnitude
3 (1001 - 5000 fish killed)
Estimated Fish Killed
4,274
Kill Length
not enumerated
Valuation
$39,007.20
Investigation Expenses
$395.55
County
Appanoose
ESD Field Office
FO 5
Fisheries Office
Rathbun Hatchery
LongDD
-92.89325
LatDD
40.82249
Created Date
3/13/2019 10:45:19 AM
Last Update
3/13/2019 10:45:19 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

The cause appears to be the result of depth-related pressure changes associated with passage from the Rathbun Lake outlet. Commonly, large schools of fish orient in front of the Rathbun Lake outlet in the late fall through late winter period. When these fish are discharged as a result of lake releases there is an immediate change in water pressure which results in blood and swimbladder issues within the affected fish. This type of kill has periodically been an issue since the construction of the reservoir. Previous kills have impacted fish, ranging from dozens to up to 80,000 dead fish. In almost all cases the predominate species is Crappie. Upon initial investigation on March 4, we observed several thousand freshly dead or moribund Crappies and Freshwater Drum in and immediately below the Rathbun Lake stilling basin, indicating the kill was ongoing. No counts were made on Sunday; however complete counts were completed on the 5, 6, and 7th, at which point the kill appeared to end.