Zebra Mussels: Not the Ecological Disaster That Was Expected
Habitat and predators prevented widespread problems for intakes
and other underwater structures
WBOY-TV
8 October 2011
By Jim Ross
About 20 years ago, the first zebra mussels were found in the Ohio
River.
Based on experience with the aquatic invasive species in the Great
Lakes, the expectation was that the mussels would coat water
intakes, outfalls and almost every solid surface under the Ohio,
Kanawha and other rivers, causing millions of dollars of damage
and lost productivity.
Only it didn’t happen.
“While the zebra mussel has been a little bit of a nuisance, it’s
not been a problem for us at all from an operational standpoint,”
said Chuck Minsker, a spokesman for the Huntington District of the
U.S. Army Corps of Engineers.
AEP spokeswoman Melissa McHenry said her company’s installations
on the Ohio and Kanawha rivers have not had as many problems with
the small mollusks as it has had elsewhere. The company developed
ways of using water flow and temperature at its intakes and
outfalls to prevent colonization, and it has been able to use
biocides to clear out those that have attached themselves to
underwater structures, she said.
So what has been a significant problem in the Great Lakes has
turned out to be a minor nuisance in the Ohio River and its
tributaries.
Jeff Kovatch, an assistant professor of biology at Marshall
University, said it’s not clear why zebra mussels didn’t spread as
much in the Ohio River basin as they did in the Great Lakes, but
there are several theories.
First is the nature of the Ohio River itself, he said. Zebra
mussels need to attach themselves to solid objects, but much of
the Ohio River bottom is mud, and sedimentation can add to the mud
already there, Kovatch said.
“They can’t move. Once they’re buried, they die,” he said.
Then there is the fact that some predators find them tasty and
easy to harvest, Kovatch said. Ducks like them. So do freshwater
drum and maybe catfish. Muskrats find them tasty, too.
“Muskrats are one of the main predators for freshwater mussels, so
they likely developed a taste to these things if they’re
abundant,” he said.
Mussels native to the Ohio River tend to have thick shells.
Muskrats will drag them out of the water and leave them to die on
land. When the mussels die, their shells open, and the muskrats
can eat the flesh inside. Zebra mussels, however, have thin
shells, so muskrats probably can crack them open with their teeth,
he said.
Then there is the fact that zebra mussels and native mussels have
different life cycles, Kovatch said. Native mussels grow and
reproduce slowly, and they have relatively long lives. Some native
species live up to 80 years, he said. Zebra mussels, on the other
hand, live fast — perhaps five years max — and reproduce quickly.
One thing researchers have noticed is that most zebra mussels in
the Ohio River are small, Kovatch said. In other waters, they can
grow to a length of 3 to 4 centimeters. In the Ohio, the majority
are the size of the nail in a small finger, he said.