Low water, hot weather make conditions ripe for fish kills in
Illinois rivers, streams and ponds
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[July 02, 2012]
SPRINGFIELD -- The anticipated long
stretch of hot, dry weather and low water levels in Illinois will
set the stage for fish kills this summer in water bodies from small
ponds to large backwater lakes along large rivers in the state. The
Illinois Department of Natural Resources is already responding to
reports from private pond owners of summer fish kills and is
anticipating more calls in the coming weeks.
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Summer fish kills are reported almost every year, and most are
caused by low oxygen levels in the water. As temperatures rise and
less rain falls, the water levels and oxygen levels drop in ponds,
lakes, rivers and streams, resulting in increased stresses on fish.
Algal blooms are also typical and further deplete oxygen levels in
bodies of water.
The IDNR Division of Fisheries receives thousands of calls each
year from private pond owners who notice dead fish in their ponds
and assume that chemicals may have somehow entered their pond. This
is seldom the case. Ninety-nine percent of summer fish kills are due
to the natural conditions that have reduced the oxygen levels below
what fish can tolerate.
"Typically, the pond owner doesn't notice anything unusual until
one July through September morning, and then fish are either belly
up or are gasping for air," said Dan Stephenson, IDNR fisheries
biologist. "The largest fish are affected first. Generally, pond
owners will see the large channel catfish die first, followed by
bass, then bluegill, and working its way down to the smallest fish
as the oxygen levels get lower and lower."
A summer kill seldom results in 100 percent mortality of the fish
in a pond but may throw the predator-prey relationship out of
balance, so future fishery management may be needed to restore that
balance, Stephenson added. If pond owners experience a summer fish
kill, they can contact local IDNR fisheries biologists for
recommendations.
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Just like fish kill events in private ponds, summer kills happen
in backwater lakes, rivers and streams as fish get trapped in pools
that grow smaller and smaller as intense heat evaporates the water.
Not much can be done to prevent the fish kill during times of
persistent hot weather and lack of rainfall.
Farmers and others who handle chemicals or animal manure can take
precautions to prevent further effects on surface waters and fish.
Farmers should check for discharges from chemical mixing stations
and areas of livestock concentration to make sure those discharges
cannot reach ponds and streams, especially when there is rainfall.
[Text from
Illinois Department of
Natural Resources
file received from
the
Illinois Office of
Communication and Information]
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