TRAVERSE CITY, Mich. (AP) — A small number of Asian carp
might be enough to establish a population in the Great Lakes that
eventually could pose a serious threat to other fish species and the
region's economy, a Canadian scientist said Monday.
Researchers at the University of Waterloo in Ontario said in a paper
published this month that under the right circumstances, as few as 10
Asian carp that find their way into one of the Great Lakes would have a
50-50 chance of becoming established. If 20 fish slip inside, the
probability of gaining a foothold could jump to 75 percent, the study
The findings show how difficult it will be to shield the Great Lakes from
the invasive fish over the long term — and the importance of developing
rapid-response procedures that could limit their spread, said Kim
Cuddington, an ecologist and the study leader.
It's probably "only a matter of time before the population migrates to the
Great Lakes," Cuddington said. "We need to start thinking about how to get
rid of a spawning population. Once you have large breeding populations in
a couple of locations, I don't think you'll get them out."
Bighead and silver carp were imported from Asia to the southern U.S. in
1970s to control algae in fish ponds and sewage lagoons. They escaped and
have infested most of the Mississippi River and many of its tributaries,
including the Illinois and Wabash rivers, which could provide linkages to
Lake Michigan and Lake Erie.
Authorities have spent nearly $200 million on electric barriers and other
measures to block the carp's paths.
Scientists differ on how many would be needed to form a growing Great
Lakes population. Males and females would have to find each other in
tributary rivers with fast, turbulent currents where fertilized eggs would
stay afloat long enough to hatch. Cold temperatures and lack of food could
Because of such obstacles, some experts say it could take hundreds of carp
reaching the lakes to become established. In their paper, Cuddington and
her colleagues said they developed mathematical models that suggest far
fewer fish might be needed.
Each of the lakes has about 10 rivers suitable for spawning — a favorable
number for males and females to find one another, they said.
Duane Chapman, an Asian carp expert with the U.S. Geological Survey who
wasn't involved with the study, said its findings are based on the
unproven assumption that a few carp — perhaps just one male and one female
— would mate. Asian carp tend to spawn in large groups, he said.
"We know there can be hundreds of fish spawning in the same place at the
same time, but we don't know if there's a minimum number," Chapman said.
Another crucial factor is how quickly the carp would reach sexual maturity
in the lakes, Cuddington said. If they mature and spawn by age 3, it could
take 20 years to establish a moderate-sized population and twice as long
for the population to become very large. But the carp could take longer to
develop in cooler waters, requiring a century or more to spread widely.