Asian carp leap from the water to avoid getting shocked by electrofishing USFWS agents in Missouri. (Credit: U.S. Fish and Wildlife Service)
Listening to scientists discuss the challenges presented by invasive Asian carp, you could easily confuse these conversations for war-room strategy sessions. Through a series of verbal exchanges peppered with tactical-grade language and anxiety, the consensus is that methods used to prevent bighead and silver carp from establishing themselves in the Great Lakes have so far been insufficient. While some of the strategies and techniques were innovative, there are questions about whether they were introduced too slowly to be effective.
If Asian carp enter the Great Lakes, the region risks threats to its biodiversity, its $7 billion fishing industry, and the tourism industry dependent upon it.
“Necessity is the mother of invention, right?” says Tory Gabriel, fisheries outreach coordinator for Ohio Sea Grant. “It’s sad we’re at this point where it is so pressing, but we are.”
Courts have been ruling against drastic anti-carp measures for a while, saying that the fish weren’t close enough to the Great Lakes to require them. However, there are indications that some carp may have made it north to Chicago and Lake Erie. A few eDNA hits -- that is, DNA sifted from water samples -- have shown up in places like Sandusky Bay and the Maumee River.
Regardless, the measures put in place so far throughout the water systems -- permeable underwater wire gates and electroshock barriers being the most common -- have been deemed insufficient.
The U.S. Army Corps of Engineers recently released a 232-page report outlining eight strategies for controlling 13 aquatic nuisance species (ANS), including the carp. The report focused on the Chicago Area Water System (CAWS), where a man-made connection between the Mississippi and Great Lakes water systems presents the easiest pathway for carp into the Great Lakes.
Even the least intensive option, a mix of chemical and biological technologies, would require 25 years and as much as a staggering $18 billion to complete, mostly due to costs involved with redesigning sewage systems in Chicago. Risk-reduction estimates at 5, 25, and even 50 years are speckled with asterisks showing that ANS colonies are still likely during earlier stages of construction.
“Twenty-five years is unacceptable,” says Jared Teutsch of the Alliance for the Great Lakes, a nonprofit collective of scientists and educators. “We need urgency and a process to move forward quickly to stop the spread of Asian carp and other aquatic invasive species.
Great Lakes residents have watched apprehensively ever since the imported fish began heading north. The carp's voracious appetite for algae and animal plankton made it an environmentally friendly cleanup tool for dirty fish farms along the Mississippi, but that same appetite makes it lethal to competing native fish species and the lakes themselves.
Asian carp eat low on the food chain but can weigh up to 100 pounds, outcompeting smaller fish. Worse, there are some indications the invasive fish could aggravate the harmful algal blooms that plague many of the Great Lakes. Some noxious blue-green algae have protective coatings that allow them to survive the carps’ digestive process while accessing nutrients picked up during filter feeding. Bighead and silver carp have no natural predators, and researchers estimate it would only take 10 of these carp to start a spawning population.
Asian carp started creeping north after escaping from fisheries along the Mississippi and Ohio Rivers during floods in 1993. Today, Asian carp make up 90 percent of the fish biomass in the Mississippi water system.
“They breed like mosquitos and eat like hogs,” says Kristy Meyer, managing director of agricultural and clean water programs for the Ohio Environmental Council.
Because of this, engineers have been encouraged to develop just about any solution to keep carp at bay -- or out of one.
One such solution was the electric barrier in the Chicago Sanitary and Ship Canal, which was meant to keep Asian carp from swimming through the CAWS and into Lake Michigan. Of the identified 18 points of entry into the Great Lakes, the Army Corps believes the CAWS point is the most critical.
The barrier consists of three electrodes arranged in a line. These electrodes power a barrier much like an electric fence for dogs. Fish swimming into it receive an electric shock sufficient enough to stun them and keep them out -- in theory. According to a report issued by the Army Corps in December, 2013, the barrier is effective against adult carp, but smaller fish of two to four inches long were able to find a loophole.
Every day, dozens of barges sweep up and down the Chicago Sanitary and Ship Canal; and when something as large, dense, and metallic as a barge passes through, the “electric fence” is temporarily disrupted. Disruptions have been significant enough that other fish species have been able to swim through the barrier alongside or in the wake of barges.
The same report notes the electrical field might not even be strong enough to incapacitate fish, despite the fact that its voltage had already been cranked up once before, in 2011. Also, power outages are a concern: an outage in 2012 put the barrier out of commission for 45 minutes.
It’s not the first time this kind of technology has failed. In the early 2000s it was used to try to get rid of gobies in the Great Lakes, another invasive aquatic species. But by the time the Army Corps of Engineers erected the barrier’s electrode system, the gobies had already infiltrated the Mississippi water system via Lake Michigan. Due to slow implementation, the barrier was never truly put to the test.
Debating the Best Defense
With carp gaining on our best defenses, many environmentalists are concerned that the GLMRIS study wasn’t intended to lead to a decision directly, and that it’s still possible that nothing will be done to combat carp at the federal level.
“[The Corps’] task from Congress was just to come up with possible scenarios,” clarifies Christopher Winslow, assistant director of the Ohio Sea Grant program. “So even in the GLMRIS report, all they're saying is, ‘these seem like logical and feasible approaches.’”
The report, already years in the making, leaves room for ambiguity about actual execution of the plans -- only 5 percent of each of the eight options has been designed. Meyer worries this will stagnate the construction process.
“We don't want to see them now say, ‘Okay, well, let's select [a plan] and do a few more years of the study to make sure that it's even feasible,’” Meyer says.
It’s a big risk to take when plans require billions in funding. Still, an appropriate plan may pay off in the long term. Recent studies suggest that controlling the spread of invasive species already present in the Great Lakes can cost up to $800 million annually.
“It's just like in medicine -- prevention is worth a pound of cure,” Winslow says. “Once they get in here … it might ultimately be less expensive to write that price tag off now than it would be to incur the annual upkeep.”
Environmentalists aren’t endorsing irresponsibility, but they do want action, and they worry that now is not the time for strict protocol or evaluation of every possible technology.
Of all the methods presented, the most experimental involves a device called the GLMRIS Lock. Barges traveling between water systems would enter a lock, have all the water with them drained, and then pass into a bed of treated, clean water. It’s also the plan that gives most pause to environmentalists like John Stark, freshwater director of the Ohio arm of The Nature Conservancy.
“My concern is, when you read the description of what they would have to do and the system that would supply it, it seems to me there's all kinds of areas where that system could potentially fail,” Stark says. Between dependence on electricity, the prospect of mixing treatment chemicals incorrectly, and pipes breaking, Stark doesn’t see the lock as a sustainable choice.
Building Barriers that Work
Two solutions proposed in the GLMRIS report reflect the calls of activists and some scientists by including a sought-after mechanism: complete division of the Mississippi and Great Lakes water systems at critical entry points.
“It's not even just for Asian carp -- you want to separate these two basins as much as possible for all invasives, ones that are there now and ones that might be in the future,” Tory Gabriel of Ohio Sea Grant says. “But ideally the best thing would be to physically separate the two watersheds, like they were naturally.”
While technological prototypes abound, hydrologic separation calls for a simple earthen-and-concrete barrier built up between water systems. Locks, bubble jets, and electroshock barriers offer possibilities of migration, but it’s pretty hard to swim through solid ground.
Barriers are much more sustainable and less involved than other suggested technologies, says The Nature Conservancy’s John Stark. They aren’t simple to build, but they don’t require as much upkeep or engineering as pipe systems and treatment plants.
“The trick with the barrier itself is that they'll have to physically move cargo from one side of the barrier to the other, and potentially boats,” Stark says. “Nothing is going to be absolutely 100 percent, but this [hydrologic] barrier's probably as close as you can get.”
In order to complete hydrologic separation in the CAWS -- the most critical entry point between the Mississippi and Great Lakes -- Chicago would have to redirect its entire septic and water system back toward Lake Michigan. The only reason the two water systems connect at all is because the city redirected the flow a century ago for septic purposes. But with significant shipping interest in the city today, it has been difficult to pass barrier legislation.
“It's easy to say that you could just go in and physically separate any water that connects the two basins, …but it's never that easy,” Winslow says. “There’s always conflict of interest and different user groups, and money's always an issue.”
But one thing is clear: while people debate the pros and cons of creating new barriers, Asian carp continue to barrel through existing ones.