Fish Kill

This article was originally published on August 6, 2012 and expired on September 30, 2012. It is provided here for archival purposes and may contain dated information.

Many people are starting to report massive fish kills around the United States. It is not a surprise to experts who recognize the water habitats, whether they be ponds, lakes or rivers, are suffering with low water levels and rising temperatures.

"Often when fish kills are reported, in a more normal weather pattern, experts start looking for point or non-point source pollution as possible causes, if nothing else just to rule them out. In a situation with excessive heat and drought we don't have to look for a problem," according to Peggy Doty, University of Illinois Extension Educator.

Reduced water amounts along with high water temperatures don't carry enough dissolved oxygen for the fish to utilize. As one would expect, the fish that need the most to sustain themselves often die first. Large catfish may go first followed by bass and finally the pan fish. Private pond owners may notice nothing unusual one day and find piles of floating fish the next. There is not usually a one hundred percent kill in any one body of water, however the predator prey balance may get thrown off enough that a fishery management plan for restocking may be in order for the following year.

It is also the time of year when we get algae blooms. An algae bloom simply means a mass amount of small aquatic plants, many of which are microscopic, growing rapidly at the same time in an aquatic environment. We tend to recognize them when they are bright green and floating just below the water surface, but some species may be red, brown or sometimes yellowish in color. Because algae is a plant it too requires the already reduced oxygen from the water. Doty adds, "If that isn't hard enough for the fish and small aquatic beings, when the the algea dies bacteria are then needed to consume it and they too require oxygen." This is one more way of proving how a drought can effect so many levels of our existence.

Source: Peggy Doty, Extension Educator, Energy and Environmental Stewardship, psdoty@illinois.edu

Pull date: September 30, 2012