“It would be a really horrible problem. People’s enjoyment of these rivers would be lost for the indefinite future.”
• • •
Friday morning, Sorensen and postdoctorate research fellow Dan Zielinski, along with recent U fisheries graduate Daniel Krause, walked amid tanks large and small at the U’s research lab. Common carp swam in some, bighead carp in others. Cross the movie “Jaws” with Shark Week and you get the picture, creepy-wise.
In one tank, Zielinski was testing whether air bubbles can slow the advancement of carp (they can). He also hoped to determine how much water current is needed to forestall carp from swimming upstream.
This last is important because Sorensen believes Asian carp perhaps can be prevented from swimming upriver through dam gates — the “doors” in dams that allow water to flow downstream — if the velocity of water flowing through them is fine-tuned.
This could be accomplished by tamping down the gates to “squeeze” water and increase its speed.
If all dams between #1 (the Ford Dam in St. Paul) and #8 are adjusted to increase velocity and work as a “system,” Sorensen believes, then perhaps another battle in the carp war can be won.
“We’ve already done some swim tests of carp down in Mississippi,” Sorensen said. “We plan to do more. But the early results indicate that Asian carp aren’t particularly strong swimmers. They might even be pretty ordinary. More like a walleye, and less like a salmon that swims upstream to spawn.”
To model optimal water velocities flowing through multiple dam gates between the Twin Cities and Iowa, Sorensen and other U researchers will employ the U’s supercomputer, a project funded by the LCCMR that will begin July 1.
A parallel effort to determine swimming capacities and other traits of native fish such as sturgeon also will be undertaken to ensure they are unaffected.
“Even then it will probably take us a year of modeling to see how the gates can be modulated as a system so water flows can overwhelm the swimming capability of these fish,” Sorensen said.
Skeptics abound. Some believe even a highly regulated lock and dam system, replete with speakers, can be overwhelmed by Asian carp, particularly in spring and other times of high water.
Others believe only research leading to development of a pathogen — a species-specific poison, in effect — is the answer. And the recent, mysterious die-off of 500,000 Asian carp in Kentucky suggests such a killer might exist.
But Sorensen says the war against Asian carp is in danger of being lost in the near term, and that anything that will keep reproducing numbers of the fish far downstream is worth trying while other strategies are developed.
Toward that end, closing the Upper St. Anthony Lock will be effective. But it does nothing to save either the Minnesota or St. Croix rivers, whereas the speaker and gate-modulation system, if successful, would.
Sorensen, meanwhile, appears to be taking in stride his recent reassignment from director and research scientist at the center he founded to that of research scientist alone, his specialty.
“Nothing’s for sure in this fight,” he said. “Ultimately, a coordinated set of multiple tools will be needed. But I see a way forward.”