(Lewis) The hot and dry weather this summer is setting up for fish kills in area farm ponds. Bryan Hayes, a Fisheries Biologist with the Iowa Department of Natural Resources, says the heat is pushing surface water temperatures up to 82-degrees.
“That’s what causes summer fish kills, oxygen depletion,” said Hayes. “For example; if 80-degrees saturation point of oxygen in water is about eight parts per million. At 50-degrees it’s 14 parts per million, so cooler temperatures hold more oxygen.”
Hayes says the warm water temperatures coupled with low water volumes can spell trouble for farm ponds. “Twelve to six inches taken off the top of a pond can be a significant per portion of the total water volume,” said Hayes. “So less oxygen and less water volume can cause fish kills.”
Hayes says restocking following a fish kill may not be necessary. He oftentimes says the fish kill is not complete, and the live fish may naturally repopulate the pond. He says pond owners need to evaluate what survived and look at the small fish in shallow water.
Hayes says to date, they haven’t had many fish kill reports, but the conditions are right, especially the older ponds that have accumulated and nutrients and sediment that can choke out the oxygen.
