Carpe Aqua: Asian Carp, Invasive Species, and the Great Lakes

By Daniel Macfarlane

Invasive species in the Great Lakes have been a big problem for decades. From the alewife, which first appeared in the Great Lakes in the 1800s, to the zebra mussels in recent decades, the composition of the Great Lakes biomass has been constantly in flux. And the problem is about to get bigger – literally, as Asian carp are knocking on the doorstep.

Granted, “invasive” species is a subjective term. The pernicious sea lamprey, for example, may well have been native to the lower Great Lakes; conversely, exotic species – such as the Pacific salmon, stocked in the Great Lakes to support sports fisheries – aren’t considered “invasive.” Basically, when we don’t like the consequences of new types of flora and fauna, even though most are introduced because of human actions, we call them “invasive”.

Asian carp.  Wikimedia Commons.

Asian carp. Wikimedia Commons.

Great Lakes newcomers have tended to enter through canals, either moving in the water via locks or hitching a ride in the ballast water of vessels. Asian carp are no exception: during the 1970s they were purposefully introduced into the American South to act as natural vacuums in fish farms. By the 1990s the carp had escaped and have since been inexorably working their way northward up the Mississippi River and its tributaries. The most prominent means, or vector, for the carp to get into the Great Lakes is via the Chicago Sanitary and Ship Canal.

Asian carp is a catchall name for a number of different types of carp, with bighead and silver carp the most worrisome. These up-to-a-meter long carp are resilient and prolific: they reproduce at astounding rates (i.e., up to a quarter-million eggs per year), live for several decades, and can daily eat 20% of their upwards-of-100-pounds weight. Silver carp also notoriously jump en masse out of the water when startled by boat engines.

The carp don’t actually eat other fish, but devour plankton. As a result, carp can out-compete native fish species, causing major repercussions along the food chain. This would be disastrous for both specific Great Lakes ecosystems and human interests such as tourism, recreation, fisheries industries, etc.

While carp probably couldn’t tolerate much of the cold, deep-water habitat in the Great Lakes, they would find nearshore and tributary habitats to their liking (and there is evidence that grass carp have already arrived in Lake Erie and are reproducing). Once they infiltrated the Great Lakes it would probably take years for the carp to gain a foothold and maybe decades to spread throughout all the lakes. Nonetheless, even if their impact wouldn’t be immediate, it could eventually be catastrophic.

Water meter encrusted with zebra mussels.  Wikimedia Commons.

Water meter encrusted with zebra mussels. Wikimedia Commons.

Out of the almost 200 alien species that have arrived in the Great Lakes–St. Lawrence basin since the early nineteenth century, it is estimated that about 1/3 have done so since the opening of the St. Lawrence Seaway in the late 1950s. Zebra mussels, which change the water quality and clog water intakes, are perhaps the most prominent. Older alignments of the Welland Canal had allowed exotic organisms such as the sea lamprey and alewife to move between Lake Ontario and Lake Erie (particularly after the re­working of the water supply for the third iteration of the canal allowed organisms to pass around Niagara Falls) and then to the upper Great Lakes.

The development in the 1950s of a lampricide (a chemical that targets and kills their larvae) has controlled sea lamprey populations. Though the lampricide is an example of a successful transborder solution, it doesn’t really provide a model for future approaches. Moreover, it is arguably emblematic of the technological/scientific hubris that created such problems in the first place. There have been a range of other attempts to combat certain new species by introducing other species, with very mixed results.

Sea lamprey.  Wikimedia Commons.

Sea lamprey. Wikimedia Commons.

Most of the recent newcomers arrived via the ballast water of foreign vessels coming in through the Seaway. As Jeff Alexander has shown,this was recognized decades ago, and if simple regulations for ballast water had been instituted by the Canadian and American authorities, many invasions could have been prevented. But it was only recently, after decades of stalling, that laws were passed requiring Seaway ships to flush their ballast water before entering the St. Lawrence River.

We seem to going down the same path with the Asian carp and the Chicago Sanitary and Ship Canal. Completed in 1900, this canal stands as the first major work of the 20th century regarding Great Lakes water control. The purpose was to provide sewage disposal for Chicago (as well as navigation and small-scale hydro production), as the fast-growing city had been experiencing major epidemics since its sewage and stockyard effluent went into lake close to the intakes for the municipal water supply.

Map of Chicago Sanitary and Ship Canal and Chicago Diversion.  Copyright: Great Lakes Fisheries Commission.

Map of Chicago Sanitary and Ship Canal and Chicago Diversion. Copyright: Great Lakes Fisheries Commission.

This canal was a significant engineering achievement since it reversed the flow of the Chicago River, taking water away from Lake Michigan – the so-called Chicago Diversion. The inverted water crossed from the Great Lakes to the Mississippi River basins, removing the hydrological separation between the two, eventually ending up in the Gulf of Mexico.

Since the canal and diversion together lowered the water levels by several feet in the Great Lakes-St. Lawrence system, they quickly drew opposition from Canada and other U.S. states (not to mention the downstream city of St. Louis, which was on the receiving end of the reversed sewage flow). This issue would repeatedly flare up throughout the 20th century in both domestic and bilateral politics.

The Chicago Diversion was effectively limited by a 1930 U.S. Supreme Court decision to a discharge of 3,200 cubic feet per second (cfs) on an annual basis. Over the following decades the volume fluctuated, however, sometimes to its maximum capacity of 10,000 cfs (at this rate the amount of water in an Olympic-sized pool is taken out of the basin in less than 10 seconds). In the 1990s it turned out that Chicago was often exceeding the stated diversion limits; as of late, however, it has apparently been kept within its legislated bounds.

In the last few years a number of American states have gone to court to try to force Illinois to close the Chicago canal because of its potential as an Asian carp conduit. But legal avenues have met with little success to this point. Others are taking more of a turn-a-lemon-into-lemonade approach: catching the carp for use as fertilizer or food, and actually exporting the fish to China where they are considered a food delicacy. And some communities hold carp fishing derbies. None of these efforts, however, have made a dent in the carp population.

The main preventative measure to keep carp from infiltrating further up the canal are electric underwater barriers installed in 2011 just miles from Lake Michigan by the U.S. Army Corps of Engineers. This barrier sends out different levels of electronic shocks designed to stun fish and prevent their passage. But the effectiveness of this barrier doesn’t exactly instill confidence. Would a fish be protected from shock if it was swimming between two vessels? Or if a fish was pulled through in the wake of a vessel, which was recently reported? What about a large school of fish, or a particularly persistent fish? Or in the event of a power outage?

Proponents of keeping the Chicago canal open claim that it contributes almost $2 billion and more than 17,000 jobs to the economy. This is surely an inflated claim because the canal receives relatively little shipping traffic. And even if we take those figures at face value, and focus on only the economic consequences, the cost of combatting other non-native species in the Great Lakes indicates that the expense of Asian carp getting into the Great Lakes would be much, much higher than $2 billion. The Great Lakes provide drinking water for 40 million people, and the fisheries are worth $7 billion annually. That is to say nothing of the recreation, tourist, or industrial interests, much less the ecological health and biodiversity of the lakes.

The history of the Great Lakes teaches us that the barrier is clearly a band-aid solution. It is astounding that, knowing the potential impact of the carp, the canal hasn’t been closed. Since it is just a matter of time until fish get through the barrier – and they may have already – this is the only sensible option.

While we must take action, we also need to be careful about how we enlist technological and scientific solutions. Beware the rule of unintended consequences: efforts to control nature in the Great Lakes, either through trying to engineers water levels/flows or introduce one species in order to neutralize another, tend to create new problems as large as those they were intended to solve.

Transborder cooperation and governance, both anticipatory and reactive, can help deal with new species. A number of existing governance bodies – International Joint Commission, Great Lakes Fisheries Commission, or Great Lakes Compact – are means for doing so. We should be taking steps to minimize vectors for invasive species while realistically recognizing that, with increasing global trade, the number of foreign species arriving in the Great Lakes basin is likely to increase. But effective active will also require a willingness to step back from a growth-and-jobs-at-all-costs mentality. The Great Lakes are worth it.

Daniel Macfarlane is currently a Banting Postdoctoral Fellow at Michigan Tech University, and will be starting a tenure-track position at Western Michigan University. He is the author of Negotiating a River: Canada, the US, and the Creation of the St. Lawrence Seawayand is involved in various research projects on the history of Niagara Falls, Great Lakes water levels, the International Joint Commission, and Canadian-American environmental relations.

5 thoughts on “Carpe Aqua: Asian Carp, Invasive Species, and the Great Lakes

  1. Sean Kheraj

    I’m glad you pointed out the social and cultural constructions of ‘invasive species.’ It reminds me of some of the environmental history literature on weeds. These seem to be both plants and animals that grow in spite of human interests.

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