MINNEAPOLIS (AP) -
Scientists have found evidence that invasive Asian carp have spawned much
farther north in the upper Mississippi River than previously recorded, the
U.S. Geological Survey said Tuesday.
Asian carp eggs,
including late-stage embryos nearly ready to hatch, were recently identified
in samples collected as far north as Lynxville in southwestern Wisconsin,
which the agency said is 250 miles upstream from previously known
reproducing populations. And it said the spawning would have occurred
somewhere upstream from that site.
“The presence of
eggs in the samples indicates that spawning occurred, but we do not know if
eggs hatched and survived or whether future spawning events would result in
live fish,” the service’s Midwest regional director, Leon Carl, said in a
still awaiting the results of genetic tests to try to confirm whether the
eggs are from either bighead or silver carp, as visual analyses suggested,
though it’s possible some of the eggs are from grass carp, the statement
discovered the eggs two weeks ago while processing samples collected last
May and June as part of a larger project to identify Asian carp spawning
habitats. The eggs were found in samples taken at seven locations between
Pool 19 near Keokuk, Iowa, and Pool 9 near Lynxville. Scientists plan to
collect additional samples this year as part of the ongoing research
project, which is being coordinated by the USGS in collaboration with
Western Illinois University.
Bighead and silver
carp have infested much of the Mississippi River basin since escaping from
southern fish farms in the 1970s. They’re threatening to reach the Great
Lakes through rivers and canals, leading the federal government to spend
more than $200 million to try to stop them. They’ve been a menace to the
aquatic food chain because they eat enormous amounts of plankton needed by
Adult bighead carp
have been found in Minnesota as far north as Lake Pepin on the Mississippi,
as well as in the St. Croix River north of where it joins the Mississippi.
Silver carp have been found as far upstream as Winona, Minn. There’s been no
indication so far that either species is reproducing that far upstream.
Still, there have been calls for closing the Upper St. Anthony Falls Lock
and Dam in downtown Minneapolis to keep them from advancing farther north.