Steve Hirsch is director of the Minnesota Department of Natural Resources division of ecological and water resources. His staff directs the DNR's fight against aquatic invasive species. In the interview below, Hirsch discusses studies leading to possible development of Asian carp barriers in the Mississippi River at Prescott, Wis., and the Ford Dam.

Q The DNR recently contracted with a commercial fisherman to net the Mississippi River downstream from the Ford Dam, looking for silver carp. None was found. Was that a surprise?

A Based on the experience of other states, not necessarily. Our [eDNA] tests indicated silver carp are in the river in that area. Not finding any probably means we have a very small population there.

Q You're still awaiting other eDNA test results.

A Yes. We've tested for Asian carp in the Mississippi just above the Coon Rapids dam and at St. Anthony Falls. We expect those results in a week or so and are anxious to see them.

Q Are you still proposing to install a sonic bubbler at Prescott, Wis., to prevent, if only partially, further carp infestations of the St. Croix from the Mississippi?

A We're doing the feasibility study and required environmental review now. The review has to be done with Wisconsin. The federal government has to be involved as well.

Q The Lessard-Sams Outdoor Heritage Council has recommended that $3 million of Legacy Act money be given to the Prescott bubbler effort, provided, among other requirements, equal funding is secured from other sources.

A A number of other Minnesota state sources could contribute, including bonding and other funds. Wisconsin at this time seems uninterested in participating. Funding from the federal government is an unknown.

Q The estimate for a sonic bubbler at Prescott is about $10 million, including initial operating funds.

A Yes. And the $3 million in Lessard-Sams money, from the Outdoor Heritage Fund, in any event wouldn't be available until July 1, if it's appropriated. So I doubt we will have a bubbler in place before the beginning of the next navigation season.

Q There's growing interest also in placing a barrier at the lock at Ford Dam.

A It's a physical barrier there, except for the lock, and we think the possibility of installing a sonic bubbler or similar barrier at the lock might prevent carp from reaching St. Anthony Falls.

Q What other type of barrier could be installed there besides a sonic bubbler?

A We're hearing about the possibility of installing "water cannons'' that would shoot just before the locks open. But it's uncertain at this point.

Q What are the chances of finding funding for these barriers, if plans can be agreed on?

A Gov. Dayton is engaged in this effort, and that's a big positive. But if we're looking at $10 million at Prescott and, preliminarily, another $3 million at Ford Dam -- and that's just preliminary -- that's $13 million. It's a lot of money in these times.

Q Is there still interest also in building a barrier farther south on the Mississippi, at the lock and dam at Keokuk, Iowa?

A Bighead and silver carp are established north of there, of course, so we wouldn't be able to stop them entirely. But looking at the future, these won't be the last invasive species that come up the river. So it's possible a barrier of some kind could be installed at Keokuk to ward off the threat of these other species. Black carp, for example, are from what we know still south of that point.