The end of summer can be a difficult time for underwater dwellers.
When temperatures are high and oxygen levels are low, fish and other water critters are particularly vulnerable. That’s been the case in Iowa this summer, according to a news release from the Iowa DNR.
“We have received several reports of small summer fish kills at many lakes, ponds and a few streams throughout Iowa,”said Chris Larson, fisheries supervisor for the DNR in southwest Iowa. “We have also had some fish kills caused by pollutants.”
Seeing fish swim erratically and aquatic plants or algae that are dying are signs of a possible natural summer fish kill. As aquatic plants die and decay, they remove dissolved oxygen from the water.
“These partial summer kills rarely kill all fish in the pond or lake, and in a couple of years it will be back in balance,” said Larson. Usually, large fish are more likely to die from low oxygen. However, some small fish can be affected.
In the hot days of summer, even small amounts of polluted runoff can cause problems for fish and other aquatic organisms.
“Historically we see more fish kills in August and September,” said Ken Hessenius, supervisor at the DNR’s Spencer field office. “We’ve investigated four fish kills in the last two weeks. So we want to encourage farmers, pesticide and manure applicators, and homeowners to be extra careful when applying chemicals, fertilizers and manure.”
Along those lines, a fish kill was recently traced to an empty hog confinement building owned by Raymond Forsyth Farms Corporation of Maynard on a tributary of the Little Volga River east of Maynard in Fayette County. DNR staff found dead fish and elevated ammonia levels in the unnamed creek.
A contractor demolished the building Friday, allowing manure to flow into the creek.
“Despite the building being empty for four years, ammonia levels were high enough in the remaining liquids to kill fish,” said Tom McCarthy of the Manchester DNR field office. “The main message is to know what you are pumping and make sure it’s not toxic. Any liquids from an unused feedlot or confinement should be tested and properly land applied.”
The building owner had contractors excavate contaminated soil and remove contaminated water. By midday Monday, about 350,000 gallons of contaminated water had been pumped from the stream.
Mostly dead minnows, suckers, dace and darter, along with a few game fish, were found along the small creek. DNR found live fish and no dead fish downstream in the Little Volga River. Live fish also were noted in the unnamed tributary after pumping ended.
To avoid this and other such incidents, the DNR says to take these precautions to protect your waters:
- Avoid applying chemicals and fertilizers before it rains.
- In town, remember that storm drains go right to a stream – spills have been caused by draining home swimming pools and rinsing chemical containers.
- Follow pesticide labels for application rates and disposal. Some pesticides are toxic to fish at concentrations of less than one part per billion.
The DNR added to call the nearest DNR field office or the 24-hour spill line at 515-725-8694 as soon as possible to report a fish kill. Quick reporting can help DNR staff identify the cause of a fish kill and potentially stop a fish kill in progress.