(AP) — As scientists aboard a research boat activate an electric current,
the calm Illinois River transforms into a roiling, silvery mass. Asian
carp by the dozen hurtle from the water as if shot from a gun, soaring in
graceful arcs before plunging beneath the surface with splashes resembling
specialist Thad Cook grunts as a whopper belts him in the gut. His
colleagues duck and dodge to avoid the missile-like fish that plop onto
the deck, writhing madly until someone can grasp the slimy, slithering
critters and heave them over the side.
It's like a
scene from a Hitchcock movie — and indeed the flying carp have played
villainous roles in many a YouTube video. Biologists, however, fear a
different kind of horror story may be taking shape underwater: a war for
survival between the aggressive Asian carp newcomers and native species
important to people who catch fish for a living or fun.
"We suspect at
some point there will be a real crash in the populations of some of these
native fishes," said John Chick, an aquatic ecologist with the National
Great Rivers Research and Education Center on the Mississippi River near
While years of
study have turned up ominous signs that the carp are capable of crowding
out other species and changing ecosystems, the worst-case scenario
scientists expect to unfold hasn't yet been realized. Some scientists say
that dire predictions about the damage carp can do may be premature. That
makes the research Chick and his colleagues are conducting critical: It
likely will influence how the debate over managing waterways made
vulnerable by carp plays out in Congress and the courts.
so far has focused on rivers, where Asian carp are most plentiful. A
common method for determining which fish are in a given location is to
shoot an electric charge into the water that temporarily stuns them so
crews can scoop them up in nets. Silver carp, an Asian type known for
springing from the water when startled, manage to jump first.
decades ago to cleanse algae-choked aquaculture ponds and sewage treatment
lagoons, they escaped during floods and have marched up the Mississippi
watershed in more than two dozen states, ranging as far as Kansas and the
Dakotas. They're taking dead aim at the Great Lakes, with the leading edge
on the Illinois River some 55 miles south of Lake Michigan, although their
DNA has been found in Chicago a mere 6 miles from the lake.
got to do is look at tributaries of the Mississippi or Ohio rivers and
you'll find them," said biologist Ron Brooks of the Kentucky Department of
Fish and Wildlife Resources.
environments are hotbeds for research, and could foretell what will happen
if carp invade other waterways. What's missing, though, is smoking-gun
evidence that Asian carp will devastate other fish. Even in places such as
the Illinois and Mississippi, where carp are rampant, changes have been
while indigenous bigmouth buffalo and gizzard shad both have gotten
skinnier since the carp arrived, the buffalo's population has declined
only moderately while the shad have fluctuated. Commercially harvested
buffalo are found on grocery shelves from Alabama to Minnesota. The shad
are crucial prey for bass and other sport fish.
"When you get
a species invasion ... typically you see some native species decline or go
extinct locally," said biologist Jim Garvey of Southern Illinois
University at Carbondale. "We haven't seen that yet. We're kind of
wondering what the heck's going on."
others have found that silver and bighead carp, the most menacing of
several Asian varieties in the U.S., eat the same food as the bigmouth
buffalo and gizzard shad. A separate study detected weight declines among
buffalo and shad in the Illinois River, believed to have the largest
concentrations of Asian carp.
are looking for proof that Asian carp are at least partially to blame for
the drop-offs. "It's just a correlation at this point," Chick said.
supports the potential that the newcomers could take over the
neighborhood. Garvey and associates reported this year that Asian carp
account for more than 60 percent of the biomass — the combined weight — of
all fish species along the lower 150-mile stretch of the Illinois River.
They also make up virtually all fish longer than 16 inches.
stir unease in the Great Lakes region, which could become the Asian carp's
next frontier. Ravenous and prolific, the carp typically weigh 30 to 40
pounds but can exceed a hefty 100 pounds. They gorge up to one-fifth of
their body weight daily on plankton — tiny plants and animals that nearly
all fish eat.
Many fear the
carp would unravel food webs supporting a $7 billion Great Lakes fishing
industry. Silver carp, the ones that leap from the water with enough force
to break boaters' noses, could give the region's tourism a black eye.
damaging carp can be is important because the fight against them is
costing big bucks — and could get lots pricier.
agencies have spent more than $150 million on technology to repel the
invaders, including an electric barrier in a Chicago-area canal linking
Lake Michigan with the carp-infested Illinois River. Five states are suing
the federal government to blockade the canal, which would take years and
cost billions. Shipping and tour boat groups say that step would be as
ruinous to them as Asian carp would be to the fishing industry.
"This kind of
research gives an early warning and justification to do everything
possible to keep them out," said Marc Gaden, spokesman for the Great Lakes
Fishery Commission. "The more understanding you have of what makes these
fish tick and what's happening in the ecosystem where they've already
invaded, the closer you get to maybe discovering ways to get them under
U.S.-Canadian team Thursday released a risk analysis for the Great Lakes.
Some experts have questioned whether the lakes have enough warmth and food
to support Asian carp. But the report found that the hardy fish would find
hospitable conditions in bays, nearshore areas and tributary rivers
feeding all five of the lakes — even chilly Superior. Warm, shallow Lake
Erie, with the most abundant fish numbers, is an especially ripe target.
It could take
as few as 10 pairs of males and females to establish a successful
population if they can find good spawning areas, and more than 70 rivers
around the Great Lakes region appear suitable, the report said. If they
slip into Lake Michigan and establish a foothold, they could journey
northward to Lake Huron and southward into Lake Erie within a decade, it
also digging through online databases for clues about how Asian carp have
affected lake ecosystems in other countries. Duane Chapman, a U.S.
Geological Survey biologist, says silver carp have driven down populations
of native species in Europe similar to the Great Lakes' prized walleye and
one possible explanation for why the carp's impact hasn't been more
dramatic so far: There may be still enough food — for now — to ward off
starvation in the Illinois and Mississippi rivers, which are richer with
algae and zooplankton than most of the Great Lakes. So the expected
die-off of other fish could take years to develop, until a tipping point
damage from Asian carp is slow and often frustrating work, thanks in part
to the ever-changing nature of rivers. Fluctuating water levels, nutrient
runoff and temperatures also affect fish numbers. But researchers are
working to solve the mystery before the fish proliferate in the Great
Lakes, determined to beat the clock and prevent the feared disaster
"No one knows
for sure what would happen," Garvey said. "But we don't want to get to
that point. We're looking at some really scary scenarios."