Heat, Low Rainfall Taking Toll on Fish
Washington PA Observer Reporter
18 July 2012
Hot summer weather generally takes a toll on fish in area
waterways, but this year dead fish are being observed earlier.
As hot weather warms lakes and rivers, the amount of oxygen drops
and some fish die.
John Poister, spokesman for the state Department of Environmental
Protection’s southwest regional office, said they have been
receiving reports of recent fish kills in ponds and lakes.
“I don’t think it’s massive fish kills,” he said. “I’m hearing
more reports of dead fish by the edge of a lake.”
When there is an extended warm spell and not much precipitation,
there are always reports of dead fish, said Mike Depew, a fish
biologist with Area 8 of the Fisheries Management Office of the
state Fish and Boat Commission.
“The low oxygen is really the killer,” he said.
During daylight hours plants are photosynthesizing and producing
oxygen, but at night as plants continue to respirate, they draw
down the levels of oxygen, depleting it enough to suffocate fish.
A good rain will alleviate the program, as will cooler
temperatures. Sometimes removing some of the vegetation or
deepening a pond to hold additional oxygen might help, Depew said.
In general, older or younger fish are affected by warm weather.
While it can affect all species, trout prefer cooler water and can
begin dying once water temperature rises above 70 degrees.
Poister noted that in some polluted streams, as weather warms and
there is no rain, the ratio of pollutants will rise as the water
evaporates, causing an adverse effect on aquatic life.
One such creek now experiencing low flow is Dunkard Creek in
Greene County. Poister said the creek is running at what the
department calls its late-August level. The creek was polluted
from acid mine drainage that caused a massive fish kill three
years ago.
Earlier this week, U.S. News reported fish kills in Delaware,
South Carolina and South Dakota that were blamed on the weather.
One, in Knoxville, Tenn., reportedly killed 10,000 bluegill.
Summer is not the only season hard on fish. Winter kills can occur
when ice forms on the surface of a lake or pond and the fish run
out of oxygen. Spawning season in the spring can also stress fish,
especially if they are in a weakened condition after a harsh
winter.
Depew said the commission completed a survey of Canonsburg Lake
this year where it has stocked catfish and fingerling walleye. The
same fish are stocked in the lake at Cross Creek County Park,
where other fish populations include bass and crappie.
And, he said, fishing remains good on area rivers where bluegill,
catfish and bass are plentiful.