by T.W. Budig
ECM Capitol Reporter
The spread of the invasive fish is not without its ironies, Asian carp expert Duane Chapman explained.
Chapman, who helped draft national policy on Asian carp, appeared at the University of Minnesota Tuesday, Oct. 8, as part of a speakers’ series sponsored by the Freshwater Society.
“He (Chapman) knows one heck of a lot about carp,” Professor Peter Sorensen of the University of Minnesota Aquatic Invasive Species Research Center said.
Asian carp were originally imported into the United States in keeping with the “Silent Spring” ethos, Chapman explained. That is, the fish could eat unwanted vegetation or perform other biological chores without humans needing to rely on the use of chemicals.
The story that these imports escaped into American waters because of flooding of fish ponds is a myth, Chapman said.
Within a year of introduction, silver carp were caught in the wild, Chapman said. Silver carp – famed leapers and one of the Asian carp varieties considered invasive – are capable of jumping 10 feet in the air and emptying boats by slamming boat throttles into high, Chapman said.
In a sense, Asian carp provide verification to the history-repeats-itself theory. That’s because common carp, which dirty water by tearing up vegetation, were knowingly introduced into the United States in the 1870s, according to the University of Minnesota.
“They’re good buddies,” quipped Sorensen of the carp, saying the two groups don’t compete because their feeding habits are different.
Although flatly saying biologists are not very good at risk assessment when it comes to Asian carp, these invasive species can be controlled, Chapman said. It took years to develop controls for sea lampreys, once depleting trout in the Great Lakes, but it was done.
“We got a shot here, too,” Chapman said.
Currently, the vanguard of Asian carp on the Mississippi River is at Lock and Dam 19 in Keokuk, Iowa, Chapman explained. While dried remains of a silver carp were found this summer on a dam abutment near Winona, he noted, there’s nothing like a full-scale invasion upriver at this time.
“I wouldn’t sell my boat yet,” Chapman said. “(There are) very, very few fish upriver.”
And it remains a big question whether Asian carp can reproduce in Minnesota waters, he said.
Not that there isn’t biological potential. One female Asian carp carried more than three million eggs, and the carp can spawn at different times of the year.
“They’re really fecund,” Chapman said. This is a worry.
Asian carp are capable of filtering out 90 percent of larger suspended plant matter in water.
Because Asian carp can filter materials as small as 4 microns, or, as a decimal, 0.00016 inches, researchers are looking at developing toxins so small as to only poison Asian carp.
Studies from Europe suggest Asian carp can negatively affect game fish populations.
Asian carp can get big. A bighead carp caught in Missouri weighed 106 pounds, Chapman said.
Healthy game fish populations are considered one means of controlling Asian carp, and Chapman noted that bluegills, black bass and catfish prey on Asian carp, the latter capable of eating silver carp that are almost a foot long.
Asian carp spawn in rivers, and it’s believed the minimum length of river needed for spawning is 26 miles, Chapman said.
While taking questions, Chapman was asked about erratic environmental DNA testing results for Asian carp in Minnesota, one batch showing positive hits for Asian carp above the Coon Rapids Dam, for instance, with later testing failing to replicate the results. Chapman indicated that he interprets DNA testing results cautiously.
It doesn’t take much to get a piece of Asian carp DNA upriver, he said. More sensitive forms of testing are needed, Chapman said.
Minnesota Department of Natural Resources fisheries manager Brad Parsons, one of the panelists at the lecture, indicated that while a full-blown invasion of Asian carp into Minnesota waters could be years away, things could also change rapidly.
“No, we can’t stay hyper-vigilant,” Parsons said of the current level of focus on Asian carp. But Parsons spoke of keeping active in efforts to curb the spread of the carp.
Sorensen spoke of the state being at the beginning of the Asian carp invasion.
Minnesotans are tracking the issue. A poll released in August by the Stop Carp Coalition showed six out of 10 Minnesotans reported hearing a lot or some about a fish called the Asian carp.
While ironies exist with Asian carp, an irony of sorts also existed with Chapman’s visit. Because of the federal government shutdown, Chapman, a federal employee, came as a private citizen.
Tim Budig can be reached at firstname.lastname@example.org.