A commercial fishing operator and state fisheries employees failed to catch a single Asian carp in the St. Croix River in nine days on the water.
"That's very good news," said Tom Landwehr, Department of Natural Resources commissioner. "It most likely means there are a small number of fish in there."
Water samples from the St. Croix tested positive last month for genetic material from silver carp, suggesting the invasive, leaping Asian species may be in the river as far north as the dam at St. Croix Falls.
The commercial operator from Illinois, with experience catching Asian carp, set nets at various places from the river's mouth at Prescott, Wis., to the dam at St. Croix Falls over four days last week. The DNR also used nets and electro-fishing for five days and didn't find an Asian carp.
Landwehr said experts believe the environmental DNA (eDNA) testing used to detect the carp is accurate, but it's impossible to determine how many carp might be in the river. "They searched everywhere that looked like good carp habitat," Landwehr said. Failing to find fish might give officials a bit more time to deal with the problem, he said.
Two bighead carp, a different Asian species, have been caught in the river - one in 1996 and another April 18 this year.