NiCHE editor Daniel Macfarlane posed a series of questions to Andrew Reeves, the author of the recently-published book Overrun: Dispatches from the Asian Carp Crisis. Andrew’s answers are below.
DM: What are Asian carp? Why should we be worried?
AR: When we’re talking about Asian carp what we’re referring to are four closely related fish species from Asia that were intentionally imported to the United States from the 1960s into the 1980s.
Grass carp were first introduced in the early 1960s by state and federal agencies like the US Fish and Wildlife Service to help with aquatic weed control at golf course ponds, irrigation canals, and the intake pipes for hydro-electric and nuclear plants.
Bighead and silver carp followed a decade later in the early 1970s when a private fish producer in Arkansas first imported the fish from Taiwan with the aim of breeding and selling them to catfish farmers who were looking for a biological option to help control algae blooms in aquaculture ponds. Both of these species eat
While less is known about the introduction of black carp, we believe they were imported to the American south, either as stowaways in shipments of bighead and silver carp in the 1970s or intentionally to eat snails in aquaculture ponds.
We’re worried about Asian carp in the Great Lakes because of their uncanny ability to eat, grow, and breed, traits that will allow them to outcompete and outbreed native fish species at alarming rates. And taken together, you have four fish that are specialized and opportunistic feeders who target aquatic plants, snails, and mussels, and
DM: Why should Canadians read your book?
AR: Canada is on a different part of the Asian carp invasion trajectory, which makes it easy to think this is a problem in someone else’s backyard. But this is clearly not the case. I think Canadians will be interested in Overrun from the point of view of an invasive that, while not established in Canada yet, is too close for comfort. Why should we sit back when there’s ample reason to suspect the problem will be ours to help solve soon
And we’re already in the game. The Canadian Department. of Fisheries and Oceans and the Ontario Ministry of Natural Resources and Forestry have been working on this issue for years, cooperating and learning from our American colleagues alongside researchers at Canadian universities and specialists at organizations like the Invasive Species Centre.
DM: Impacts on the Great Lakes?
AR: The main reasons we are worried about Asian carp in the Great Lakes is because of their unique ability to target different aspects of aquatic ecosystems. So what you find with grass carp is a fish that is incredibly good at eating aquatic weeds, and so our fear is that they will target wetlands and denude them entirely.
With silver and bighead carp, however, the issue is that both of these fish are incredibly opportunistic feeders. What this means in the context of the Great Lakes is that bighead and silver will eat phyto- and zooplankton, which is the main food source for most juvenile freshwater fish species in the Great Lakes, and gobble up all of those resources. But once they have finished eating all of the phyto- and zooplankton available, bighead and silver carp find it easy enough to pivot and eat other food supplies in order to stay alive. Yet most freshwater native fishes have not evolved with that capability, and so when their food supplies run out they simply starve.
All Asian carp species are also capable of breeding several times a year in huge numbers. In addition to that, the fish typically eat upwards of 100 percent of their body weight each day, especially worrying given that these fish can routinely grow to anywhere from forty to eighty pounds or more. This all adds up to a terrible strain on freshwater fish species with fears for what they might do to a $7 billion dollar Great Lakes fishery.
DM: What are the main vectors for Asian carp to make it to the Great Lakes and what has been done at each to mitigate the dangers?
A few years back the Army Corps of Engineers studied this issue and identified roughly 18 sites where Asian carp could potentially make it from the Mississippi River system into the Great Lakes. However, just as quickly as they had identified those sites, they had dismissed all but two of them as unbelievably unrealistic, thinking it would require flooding and storms of such gargantuan proportions that if Asian carp somehow did pass through during that event it could effectively be chalked up to an act of God, as it were.
What two remained? Chicago, Illinois on Lake Michigan, which, through the Chicago River linking the Great Lakes to the carp-infested Illinois River, was determined to be the primary vector. And second on the list was Eagle Marsh, an obscure conservation area southwest of an equally obscure town in Indiana – Fort Wayne.
Let’s start with Chicago. In the early 2000s, researchers and government workers struggled to get approval for an underwater electric barrier to be installed south
It was right around the time that Asian carp
Eagle Marsh sits on the ill-defined area between the Mississippi River and Great Lakes watersheds. Soon after Asian carp became a household name in 2009, researchers realized that the way in which Eagle Marsh had historically acted as a kind of overflow area for flood waters from each basin could ultimately mean Asian carp could use the marsh to jump basins. How? Say the Mississippi system has high water events that led to flooding in Eagle Marsh, bringing whatever species (Asian carp) that live in the Mississippi waters into the marsh – and if, sometime later, the Great Lakes flooded into Eagle Marsh through a series of tributary rivers before receeding, they would bring with them whatever was swimming in Eagle Marsh (Asian carp) into the Great Lakes.
The result was a massive Asian carp fence erected in the marsh that was, in 2016, replaced by a permanent berm so large that it reshaped the subcontinental divide.
DM: How does history help explain the story of Overrun? How did your MA degree in geography shape how you approached the book?
AR: I completed
It was this interest in bringing history to life and shedding new light on old ways of thinking that propelled the early writing stages of the book, reflected in Overrun’s first three chapters that unpack the fascinating history of Asian carp in America. I didn’t imagine I would need to explore the impact of Reaganomics on the Environmental Protection Agency in order to have the story of Asian carp make sense, but when you follow the story and listen to your sources and the research itself, you’re taken in some remarkable directions.
DM: Final message for NiCHE readers?
AR: We’ve gotten pretty good at making social and regulatory changes to help address the Asian carp crisis. It’s only when we’ve been faced with more conceptual challenged necessary to halt Asian carp’s spread across North America that we have utterly failed. Everything from addressing the impacts of climate change on rainfall to the impermeable nature of our urban areas to the ways in which we grow our food and have modified our waterways – our responses to all of these issues will determine how effectively we control Asian carp in the long run.
What do these conceptual changes have to do with an invasive fish? Everything, really. Let’s start with climate change. Across the US Midwest and throughout the Great Lakes basin, cities like Chicago and Toronto can expect that changes in precipitation brought on by a warming world are seeing rainfall events become more extreme – in some cases, cities are seeing 30-40 percent of annual precipitation falling in a 24-36 hour period.
Where does that heavy rain fall? In our cities, it lands on concrete and is often ferried directly to combined sewer overflow pipes that drain rainwater and untreated human waste directly into local waterbodies. That rain also falls on our farmland. While farmers have done tremendous work reducing the volume of fertilizer they apply to their fields to help reduce algal blooms, the problem is one of scope, in that there are simply too many fields with phosphorus and nitrogen sitting on the top of the soil, fertilizer that often gets washed into waterways during heavy rains.
What does all that fertilizer and untreated human waste do in local waterways? It speeds them up and, in the process, creates excess plant material in the water that pools together. And those Asian carp in the rivers now filled with excess nutrients? They treat these fast waters a cue to spawn, and they eat those excess nutrients like a buffet.
We can’t go on thinking we can stop Asian carp from reaching the Great Lakes by fishing them down or eating them or turning them into cat food or deterring their spread with carbon dioxide curtains if we don’t address the myriad conceptual ways in which we have (and continue to) modify and degrade our terrestrial and freshwater ecosystems. Only by thinking in ways big and small can we lift the CIRS of Asian carp in North America.
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