Restored Hennepin Wetland Showing Signs of Recovery

State fisheries crews saw many good signs last week at the restored Hennepin and Hopper lakes.

Sampling numbers
They found many small largemouth bass, northern pike, black crappies, bluegills and pumpkinseeds, fish that were recently stocked or were offspring of stockers at this refuge on the Illinois River in Putnam County.

“We were able to sample numbers of small bluegill that were obviously from our stocking effort that reproduced from the brood fish,” said Wayne Herndon, Illinois Department of Natural Resources fisheries biologist.

The small bass were 4-6 inches long, “which would indicate they’re growing very quickly,” he said. “The northern pike are up to about 12 inches in length and they appear to be pretty numerous.”

The pike are likely eating some of the small bass, “which is not all a bad thing,” Herndon said. Bass, in turn, will control any carp that might get by dikes surrounding the backwater wetland, he said.

For most of last century the 2,700-acre wetland complex was drained and used by crop farmers. In 2001 The Wetlands Initiative reconnected this land to the floodplain. In 2012 the refuge was listed as a Wetland of International Importance in accordance with the international Ramsar Convention on Wetlands.

Carp plagued restoration work. In previous years and in 2012, the wetland was drained and treated with the fish toxicant, rotenone, to extinguish these non-native fish. This week DNR crews used electro-fishing gear in three boats to sample fish and fortunately, saw no carp, Herndon said.

Further, water transparency is excellent, indicating sunlight is getting to the bottom and carp are not uprooting vegetation.

Prehistoric fish
“The surprise is we were able to sample enough bowfins that indicate they also have been able to reproduce,” he said. “If the bowfin are doing well, then we’re almost certain the gar are doing well.”

In 2010 the DNR stocked 43 alligator gar in Hennepin-Hopper. This fish, which can grow to 300 pounds and 10 feet long, once lived in the Illinois River but habitat destruction drove it out.

The bowfin and gar retain characteristics of an ancient lineage of fishes.

“Both are ancient predators,” Herndon said. “They are among the most ancient fish we have in the United States and they have similar food requirements.”

That requirement, for the most part, is any fish they can swallow.

Alligator gars grow quickly. Two years ago the DNR stocked 78 alligator gars, 2 years old and 2 pounds each, into the Powerton cooling lake southwest of Peoria. This year they caught one of the fish. It had grown to 25 pounds and nearly 50 inches long in just two years. The DNR displayed the live fish at the Illinois State Fair and released it back to Powerton, Herndon said.

This week crews also sampled 410 largemouth bass at 3-3.5 pounds each in Hennepin-Hopper. These bass will eat small carp and carp eggs. Even small bass are consuming young fish now. A bass only 5 inches long can eat a fish 1.5 inches long, Herndon said.

“That’s exactly what we wanted for control of carp,” he said.

After initial restoration work, the site was reopened to fishing in 2004 but was closed again in 2009 to allow more work.

This spring, the DNR will again sample the fishery and consult with The Wetlands Initiative.

“I don’t anticipate it opening until 2015, but we’ll re-evaluate it as we go along,” Herndon said.

Because of the site’s high-quality habitat and diversity, boating restrictions are likely, Herndon said.

Emiquon, a similarly-managed and diverse Illinois River backwater 75 miles to the southwest, allows only electric motors, he said.

Source: News Tribune