The Iowa Department of Natural Resources (DNR) has begun draining Walnut Creek Marsh in Ringgold County to make improvements in the marsh toward preventing summertime fish kills, similar to the significant fish kill that occurred in mid July. The marsh will drain over the next few weeks.
Draining the marsh will allow the DNR to remove an excessive abundance of American Lotus, a likely contributor to the summer fish kill. The DNR will also consider other potential improvements such as increasing the depth of the marsh through dredging or increasing the height of the existing dam.
The DNR will re-stock fish once the marsh has refilled.
Walnut Creek Marsh suffered a significant summer fish kill in mid-July due to low dissolved oxygen conditions caused by decaying vegetation. The DNR continued to monitor water conditions after the fish kill and it was determined that aquatic life could not be sustained under the current conditions.
Summer fish kills generally occur in small, shallow ponds with excessive vegetation. Sunny conditions during the daytime allow for plant photosynthesis that produces dissolved oxygen. However, at night, the dissolved oxygen produced during the day is used for respiration by fish, insects, plants and other aquatic organisms. After a period of calm, cloudy days, the dissolved oxygen produced may be depleted by decomposing vegetation and result in a fish kill.
Walnut Creek Marsh will not be available for fall fishing and duck hunting in 2014.
For more information, contact Iowa DNR Fisheries Biologist Andy Jansen at 641-464-3108 or Iowa DNR Wildlife Biologist Chad Paup at 515-238-5708.