Carp get the better of other fish whose
waters they invade, literally by eating
them out of house and home. This
has been disclosed by the drainage of
a small, carp-infested lake in southern Wisconsin, which was studied by
Dr. Alvin R. Cahn of the University
of Illinois. His results are reported
in Ecology.
As the waters went down in the
lake, all the fish were captured and
counted. Out of a total of 6,006 fish,
5,891 were carp. More desirable species, like perch, black bass and pike,
were notable for their absence or
scarcity. By way of contrast, a similar total taken from a lake containing
no carp had a good representation
of several desirable game and food
species.
The most notable difference
between the two lakes, Dr. Cahn
states, was to be seen in the plant
population, which of course forms
the ultimate food of all fishes. In the
carp-less lake there was an abundant
growth of many kinds of plant life,
in the carp-filled water there wasn’t
a weed. The restless, avid, all-eating
mouths of the carp had destroyed
every green thing.
The muddy bottom of the lake was
entirely covered with little semiround depressions about a quarter of
an inch deep. These had been made by
the carp, “mouthing” the mud to get
the last traces of anything fit even for
a carp to eat. Incidentally, of course,
this constant stirring of the bottom
effectually prevented the germination of any seed of a water plant that
might have fallen into the lake, and
also kept the water constantly roiled
and muddy.
Bighead carp swim freely in tanks at Chicago’s Shedd Aquarium, but major efforts are under way to keep this and other species out of the Great Lakes.
UPDATE
A new carp comes to town
Great efforts are under way to
make sure the fish, which can grow
to 100 pounds and reportedly eat
between 20 and 120 percent of
their weight in plankton and algae
each day, stay out of the Great
Lakes — where they’d probably sink
the $7 billion fishing industry.
Control strategies include elec-
trical underwater barriers and carp
hunting. (Carp-seekers beware: This
game jumps and has been known to
break noses.)
Some say the best solution is for
people to eat the Asian carp. Though
its common cousin couldn’t capture
and retain the interest of American
diners, perhaps the new invader will.
In which case the present may break
from the past after all.
— Elizabeth Quill
History indeed repeats itself, but — in
the case of invasive carp — things may
be worse the second time around.
Sometime during the 1800s, the
common carp was intentionally
introduced into American waters as
a potential food source. As Alvin Cahn
found in the 1920s, escaping carp
did well in muddy-bottomed lakes,
rooting around for food, making the
waters turbid and damaging the ecosystem from the bottom up.
Today, there’s a new invader. In the
1960s, catfish farmers brought Asian
carp to American ponds to clean up
algae. Again, the fish escaped. Bighead
and silver carp now reign in the Mississippi and other Midwest river systems.
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