SPIRIT LAKE, Iowa – A commercial fishing company caught 55 silver carp and 82 big head carp on March 28 and 29, fishing in the same general area of East Okoboji Lake where two big head carp were netted by the Iowa DNR last August during a population survey.
On April 3, one silver carp was caught by the same commercial angler in Spirit Lake. A second netting effort on April 4 in the same East Okoboji Lake location resulted in only two bighead carp and two silver carp.
Mike Hawkins, fisheries biologist with the Iowa Department of Natural Resources, said the invasive fish had a small window last summer in which to enter the Iowa Great Lakes. Flood events in June and July allowed the fish to navigate the Little Sioux River past the Linn Grove Dam, landing at the doorstep of the Iowa Great Lakes.
Once below the Iowa Great Lakes, heavy rain events in July caused flooding conditions on the lakes that allowed these fish to enter Lower Gar Lake, which is the final lake in the chain of six glacial lakes in Dickinson County.
“While it confirms the presence of both species, this commercial seine haul does not tell us how many Asian carp are in the lakes. Nor does it get us any closer to knowing at what level these fish will be a problem.,” Hawkins said.
The DNR has been working with their partners to prevent additional invasive carp from entering the lakes.
Fundraising to pay for an electronic fish barrier at the Lower Gar outlet has passed $600,000. Hawkins said information on different barriers is due April 9 from prospective companies that will explain the potential systems and more accurately set out the final cost. Preliminary estimates put the barrier in the $700,000 range.
“I can’t say enough about the effort our local partners have invested in this project,” Hawkins said. “We are working to get the barrier in place as quickly as possible but there is a process to this and we need to do it right. These are complicated and sophisticated devices and this will be a major construction project.”
Since the flooding at the lakes in July 2011, the lake levels have fallen below crest, lowering the threat of any additional carp from entering the lakes.
“Our greatest fear is that these fish could impact recreation and the ecology of the lakes. Looking back however, we know we experienced at least part of a season with them in the lake without incident,” Hawkins said.
While both species are problems for the fisheries, silver carp are more of a concern for boaters because of their tendency to jump out of the water and can grow to more than 50 pounds.
“Ecologically, these fish are filter feeders and will compete with young fish for food. They are not likely to reproduce here because studies show they prefer large rivers for spawning,” Hawkins said.
While anglers are not likely to catch one of these fish because they are filter feeders, if it does happen, Hawkins said they should bring them to the Spirit Lake Hatchery.
The invasive carp were removed from the lake and utilized by a local fish processing company.