Iowa Great Lakes to get electric fish barrier
SPIRIT LAKE, Iowa -- The Iowa Department of Natural Resources will open bids on Wednesday for the first-ever electric fish barrier to be constructed in the Iowa Great Lakes. It will also be the first in the entire state.
The barrier, to be constructed on the Iowa Great Lakes dam on Lower Gar Lake, is hoped to stop the spread of the invasive Asian carp, specifically the bighead and silver carp, from further entry into the chain of lakes. The Iowa DNR first discovered two bighead carp in East Lake Okoboji in August 2011.
Mike Hawkins, fisheries management biologist with the Iowa DNR's Spirit Lake office, was with the sampling crew when the bighead carp were pulled in during summer sampling efforts. The carp were caught in a 500-foot seine, and believed to have been only about a year old. Still, at that age, the carp already measured 14 to 15 inches in length. That compares to a 1-year-old walleye, which has grown to only eight or nine inches in the same span of time.
Hawkins and his crew were "disturbed" by the finding.
"What it told me right away was that if we caught two bigheads, there were going to be silver carp with them because they travel together," Hawkins said.
While subsequent testing last fall found no more Asian carp, the confirmation came this spring when a commercial fisherman, using a 5,000-foot-long net, caught 55 silver carp and 82 bighead carp in a single haul. The invasive carp were disposed of, but Hawkins said that catch likely had little impact on the overall population.
"With all invasive species, in a new habitat, their numbers explode and there's very little control to those numbers," Hawkins said.
One advantage going for the Iowa Great Lakes, however, is that reproduction of Asian carp appears to be confined to large rivers, including the Mississippi, Missouri and the Illinois. Hawkins said the fish spawn in the river channel and the eggs have to remain in the drift for approximately 30 days before they hatch. They also need a high water event, which is their cue to spawn.
"We don't have those in the lake," he said.
The invasive carp now in the Iowa Great Lakes are believed to have traveled 230 river miles upstream via the Little Sioux River. By taking proactive measures, such as installing an electric fish barrier, the Iowa DNR hopes to cut off the means for the Asian Carp to reach the Iowa Great Lakes.
"This is what we're faced with right now," said Hawkins, admitting that a bulk of his time in the last 14 months has been spent dealing with aquatic invasive species. "We need to try to hold the line as much as possible with these critters."
Plan of action
The electric fish barrier will consist of eight electrodes attached to the vertical wing walls on the Iowa Great Lakes dam on Lower Gar Lake. The electrodes will be spaced to span 21 feet wide by the entire length of the 165-foot dam, Hawkins said.
At an estimated cost $627,000, not including the $118,000 for design and engineering, the electric barrier will be paid for through multiple sources. The local community fundraised $400,000 toward it, and the Iowa DNR contributed $300,000. The remainder will likely come from other partners, including the Minnesota Department of Natural Resources.
Minnesota has a stake in keeping the invasive Asian carp from spreading out of the Iowa Great Lakes and into lakes in Jackson County such as Loon, Little Spirit and Clear Lake.
"This isn't a problem that stops at the state line," Hawkins said. "(Minnesota's) partnership has been amazing -- they're working very hard with us on this."
"We've got a direct connection to the Iowa Great Lakes through the Little Sioux Watershed," said Nate Hodgins, assistant area supervisor at the Minnesota Department of Natural Resources Windom Area Fisheries office. "Some of the concern was that these fish were already in the Little Sioux."
The DNR in Minnesota submitted a request to the state on Aug. 2 for up to $500,000 to help Iowa pay for the electric fish barrier.
"There was concern (about) spending Minnesota tax dollars out of state, in Iowa, but it can be done because this is a major pathway into Minnesota waters," Hodgins said. "If we can shore it up at the most logical spot with the least amount of money," it should be done.
Through cooperative efforts with the Iowa DNR, Hodgins said Minnesota has also identified locations for barriers to prevent the spread of the invasive carp.
"We had nine spots where we found we could stop the expansion of invasive species," Hodgins said, adding that four of those spots have already been blocked. Among them is Herlein-Boote Slough at the north end of the Okabena-Ocheda Watershed District, where gates were closed last winter to prevent water diverted from the Rock River Watershed from flowing toward Worthington.
The Little Sioux Watershed connects to both the Rock River Watershed and the West Fork of the Des Moines River Watershed.
"We don't want these (invasive carp) to move from watershed to watershed, and from Iowa's perspective, we certainly don't want them in the Des Moines River Watershed," Hawkins said. About three-fifths of Iowa's land mass -- and a quarter to one-third of its public owned lakes -- are in that watershed.
Hodgins said other work in Minnesota includes building up earthen dams to stop overland flooding, installing an electric fish barrier by early next spring on a culvert in the Little Sioux River in Jackson County to protect Round Lake and Indian Lake, and working with private landowners on watershed divides.
"We don't want to come in and mess anything up for anybody, but we also don't want these fish to come in and expand," Hodgins said.
Temporary to permanent
As the Iowa DNR formulated its plans for an electric fish barrier, a temporary structure was built on the Iowa Great Lakes Dam on Lower Gar to keep Asian Carp at bay.
A lake homeowner covered the entire $17,000 cost of the project, which included stringing high tensile fencing across the dam to a height of four vertical feet and another angled foot of wire to ward off the jumping silver carp.
"In late May, we didn't see any Asian carp below the Iowa Great Lakes, but we did have hundreds of them jumping below the Linn Grove Dam," Hawkins said. Linn Grove is located in northern Buena Vista County.
Hawkins said one more rain event likely would have provided the high water needed for the invasives to cross the dam and move upstream toward the Iowa Great Lakes.
"That was the impetus to get a temporary barrier in place before our electric barrier goes in this fall," he said.
Eye on completion
With bids on the fish barrier's construction due Wednesday, and interest among contractors, Hawkins is hopeful the project will be completed by mid-December.
"The electric fish barrier provides protection against big flow events that we can't do with a mechanical barrier," he said, adding that with the electric barrier, debris will flow overtop and not get clogged like what would happen if fencing was used.
The barrier will operate on DC current, a low frequency that will increase in intensity as a fish tries to make its way across the electric barrier.
"The fish experience increasing electrical field that causes their musculature to basically shut down," Hawkins explained. "They can't swim, and the current carries them back downstream."
Asian carp are particularly sensitive to the electrical field, which Hawkins said makes the barriers even more effective. In electro-fishing incidents used by the Iowa DNR this spring at the Linn Grove Dam, the silver carp were seen quickly jumping away from the electrical field.
While the DC current is relatively safe for humans, Hawkins said the area where the electric barrier is going will be fenced off to prevent people from getting near it.
"We will have signage on them warning people to stay away from it," he added. "The designer has 47 of these operational in the United States and they have not had a safety issue with them."
A warning light will activate when the barrier is on, and considering the dam has historically had flow over it half the days on record since 1930, it will not be operating all the time.
"It's only during those higher-flow events that this will be on," Hawkins said, adding that the DNR anticipates approximately $200 per month in electrical costs for the barrier, as well as security cameras that will be onsite.
If the electric barrier works as expected and keeps the Asian carp out of the Iowa Great Lakes, Hawkins said there are a couple of other benefits as well -- it will keep the common carp from getting into the lakes, and may keep some game fish from traveling downstream.
"It's not as good at preventing migration downstream as it is at keeping fish from coming upstream," Hawkins said.
Both Hawkins and Hodgins say Iowa and Minnesota are being proactive in trying to stop the spread of invasive Asian carp through steps already taken and continued sampling efforts in the Little Sioux Watershed.
"So far we haven't found any invasive carp in southwest Minnesota," Hodgins said. "I feel like we're ahead of the curve in getting these barriers in.
"Nothing is 100 percent effective that you do in resource management ... but we're very confident these barriers will be the fix," he added.
"For all intents and purposes, we don't have to stop every single Asian carp from coming in -- we just have to stop the mass of them from coming in," added Hawkins. "We believe, with the research that's out there, when (the electric barriers are) in operation, they are effective."
Daily Globe Reporter Julie Buntjer may be reached at 376-7330.