Source: YouTube
To prevent them from entering the Great Lakes, Americans even began to learn to eat carp.
For more than 50 years, carp have found almost all over the Midwestern United States, from South Dakota to the Mississippi River Delta and even in West Virginia. About 90 percent of fish in certain waters are reported to be invasive carp, and in a section of the Illinois River, one of the tributaries of the Mississippi River, invasive carp accounts for 75 percent of the total biomass in the water. They annoy people, overwhelm other fish species, muddy otherwise clear currents and, in some cases, frightened carp leap out of the water. Surface boats can scare thousands of carp as they sail by, and these big guys weighing more than 20 pounds jump out of the water and smash into the people on board, even breaking their arms and jaws in severe cases.
So far, however, this prolific fish has mostly stayed near the Great Lakes, blocked by complex continental ridges that surround the southern and western shores of the Great Lakes. Rivers west and south of the ridge flow to the Mississippi River and the Gulf of Mexico, while water to the east and north flows to the Great Lakes, which account for 20 percent of the world's surface freshwater and attract boating, fishing and other recreational activities that collectively generate $14 billion to $42 billion annually.
However, the species, formerly known as the Asian carp, still found its way to the Great Lakes. There is a year-round waterway between two major waters in the Northeast: the Chicago Sanitary and Ship Canal.
The canal opened for commercial shipping in 1900 and was expanded seven years later, with one of the unintended consequences of opening the door to invasive species like carp. The expanded canal connects Lake Michigan and the Chicago River to the Des Plaines River, which flows into the Illinois River, causing carp to flood the Illinois River.
The Brandon Road Lock and Dam is located south of Joliet, Illinois, where the canal meets the Desprance River, and carp have to cross the 30-meter-wide canal and lock to reach the Great Lakes, thus becoming a "choke point." There, the U.S. Army Corps of Engineers (USACE) is raising $1.2 billion from taxpayers to build a barrier to keep carp from invading the Great Lakes.
Experts say that the cost of keeping invasive carp out is worth it, "otherwise it will cause disaster." Greg McClinchey, director of legislative affairs and policy at the Great Lakes Fisheries Commission, reflected on the situation when invasive carp entered the Great Lakes: "Any project can be costly, but failure is even more expensive. ”
Officially known as the Brandon Road Interbasin Project, it is, in fact, the last line of defense on the Great Lakes. It will be a tough test, taking years to install and use a variety of techniques, from electric shocks to bubble enclosures (also known as barometric barriers), just to get the attacking carp to turn around and leave the Great Lakes.
"I very much hope that these technologies will work." Molly Flanagan, chief operating officer of the Alliance for the Great Lakes, a nonprofit organization, said, "One open question is whether we are building fast enough." ”
Attack on carp
Blue, grass, silver carp and bighead are Chinese well-known "four big fishes", and they are also the four invasive species of cyprinids that make Americans helpless. Although the exact date of their entry into the United States is unknown, they were indeed introduced to the United States on purpose in the early 60s of the last century. Originally, these fish were used as a kind of play for anglers. Since then, it has been used as a solution to environmental problems: herbicides have been overused to remove weeds from catfish farms in the Mississippi Delta, while carp kept underwater can eradicate weeds and eat algal blooms on the surface.
"At that time, it was thought that carp could not breed in such an environment." Brian Schoenung, aquatic species program manager at the Illinois Department of Natural Resources, said, "This is a brilliant way to eliminate chemicals. ”
In the early 70s, thousands of carp introduced to the United States took advantage of the flooding to enter the tributaries of the Mississippi River. They proved to thrive in U.S. waters, quickly wreaking havoc on waterways and native species. "They are the 'pigs' of fish." Outdoor writer Mark S. Mark C. Derts writes, "Grounding in weed-grown riverbeds eventually destroys the habitats of other fish." They swim at the bottom of the river, muddying the river, causing sunlight to not penetrate and affecting plant growth. ”
Before the passage of the federal Clean Water Act in 1972, it was not a problem for invasive species to pass through Chicago environmental sanitation and navigate canals. The 48-kilometer-long river channel reversed the Chicago River when it was first established, causing urban sewage to flow south, rather than into Lake Michigan, the city's source of drinking water. The river is so polluted that fish cannot survive in it. But the Clean Water Act more or less cleaned up America's waterways, reducing the canal's level of pollution enough to allow some dirt-tolerant species to appear.
Fish swimming into the canal also include the blackmouth new goby (Neogobius melanostomus). Coming from Eurasia, it is fierce and greedy, hiding in bilge sewage from ocean-going freighters, discharging from the hull and entering the Great Lakes.
Experts trying to stop the goby from spreading to the Mississippi River basin have come up with a dozen possible options, including introducing "biological pathogens" into ecosystems, using superheated water from power plants to make fish uncomfortable, putting toxic substances into waterways or closing canals altogether. In 1996, the U.S. Congress approved USACE to develop a fish barrier, and the advisory panel decided to build an invisible fence similar to a dog owner's backyard fence: using electrical pulses to make the fish turn around.
USACE identified a location near Romeoville, Illinois, to build the first barrier. However, not long after the start of the project, goby was already present downstream of the town of Romeoville. Imagining that the same problem could be subject to the same variables in the future, the project decided to change its target from a practical project for one species to a test project to investigate how electrical impulses affect more types of fish.
During the study, scientists tagged and bred 130 carp caught inside the canal. They monitored the carp and observed how they responded to electrical impulses. (Another observation is purely accidental: how humans react.) One barge crew tried to moor the boat near the facility using metal cables, despite warning signs. A direct spark of about 30 centimeters erupted at one contact, and if the ship was loaded with more volatile cargo, the ship could blow up directly. ）
During the testing phase, only one fish passed through this charged barrier, apparently exploiting the barge's passage into the canal. Another worrying situation, as often happens with power systems, experiences periodic blackouts for up to 56 hours, enough for schools of fish to swim through.
At the end of the test, an observer from the nonprofit American Fisherie Society concluded: "The electrical barrier solves part of the problem at best. Although the plant's operators ultimately reported that their engineering was "technically reliable, successfully repelling fish without casualties," it also suggested that further implementation could be better if combined with other types of deterrence, such as bubble or sound repulsion.
"Carp Panic"
For more than 30 years, USACE and its partners have been conceiving and testing different types of barriers to try to keep invasive carp out of Lake Michigan. During this period, there was even a "carp panic". In August 2022, fishermen reported seeing a tarpon in Lake Calumet upstream of the Brandon Road locks and dams, just 11 kilometers from Lake Michigan. Government agents sent a small team and eventually caught the fish. After weeks of searching, no other carp were found, much to everyone's relief.
Adult and juvenile tarpon. Source: Katie Steiger-Meister/USFWS
Later, Illinois and Michigan added new programs to their proposed state budgets, with an estimated $114 million budget to Brandon Road to cover the local matching costs needed to kick-start the next federal cash flow. As a result, the project's previously set cost of $778 million increased to approximately $1.2 billion.
As currently envisaged by the project, carp swimming upstream will encounter a series of obstacles up to 0.8 kilometers long. The purpose of each dish is to "dissuade" most of the carp so that the number of carp that continues to advance will gradually decrease until it all disappears. The researchers believe that even if carp eventually reach the open water upstream, they won't be able to find each other, let alone reproduce in large numbers. The multi-defense system also provides layers of redundancy in case of any system failure.
"To stop all the carp, we can't win in one move." Marc Cornish, a senior technologist and biologist at USACE, said this is a big truth because the waterway is open to other vessels.
Near the entrance to the main road of the downstream sluice, the carp will encounter the "first line of defense". This is a set of combined barriers: a thick bubble curtain, plus a drained speaker, emits noise at a certain frequency and volume to drive away the invading carp. Experts estimate that the acoustic barrier can repel 99.5% of invading carp, and further adjustments can eventually increase this figure to 99.9%.
If thousands of fish are crowded in the river, this means that very few fish can pass through the barrier. The carp will find themselves swimming into an engineered river. Within a radius of a few hundred meters is a box channel made of concrete, where fish are virtually unable to inhabit. There are no rocks that stand out to block the flow of water to allow the fish to rest, there is no food source, and in the eyes of the fish, there is no incentive to attract it forward.
Bio-acoustic repellent barriers are being installed to deter carp and drive them away through bubbles, light stimuli and noise. Source: Kristen Peters/USFWS
If some fish pass through the first barrier and enter the sluice, there is a second, larger acoustic array waiting for them. And if any fish wanted to take advantage of the gap between barges, as the goby tested in Romeoville did, it is not feasible now, because the lock itself has been modified to become a "washout gate", under the physical thrust, even the tiniest creatures will be washed back downstream.
However, if, after all this, some fish continue to swim upstream, from the canal all the way to Lake Michigan, to the town of Romeoville, 16 kilometers away from the Brandon Road locks and dams, they will hit the grid array, which is quite a long journey for exhausted fish.
Eat it
In addition to the huge underwater works, the locals are also "consuming" carp in other ways. In the upper and lower reaches of the Mississippi River and its tributaries, carp are caught at an alarming rate. In Kentucky, for example, more than 4,500 tons of carp were caught in 2021 and 2022. Schönnon also said that 5,000 tons of carp were caught in the Illinois River downstream of the Brandon Road lock in 2019.
A U.S. WILDLIFE official carries a bighead carp weighing nearly 50 kilograms. Image source: USFWS
The Illinois Department of Natural Resources has launched a campaign to encourage the consumption of invasive carp. In Asia, carp is a delicacy, so officials hope that customer demand will spur the growth of commercial fishing, and even renamed it "copi" (from the word copious) in hopes of boosting consumption.
"Our commercial fishing projects are having some measurable impacts, which have some inhibitory effects on carp populations, but it's hard to quantify." "We have to deal with a lot of variables, and you have to ask, is it better to reallocate funds to remove fish stocks, or is it better to study the impact of fishing?" We don't have enough money to do both. ”
The aim of all these activities is to reduce population pressure on carp and allow them to find new habitats. This is important because, according to current plans, the actual start of the project will not begin until October 2024 and will not end until July 2029.
The first phase is the installation of a bubble enclosure and a narrow acoustic array at the lower entrance of the channel, which is theoretically completed by the end of 2026. The second phase expands the electrode array, builds a second acoustic barrier, and reshapes the locks to allow barges to pass and flush carp back downstream. The final phase involves rebuilding the river to make it difficult for carp to pass, which will require temporarily shutting down barge traffic and perhaps blasting some bedrock to improve the system. If all goes according to plan, the construction will be complete by the summer of 2029.
Today, invasive carp can often be caught in the downstream dam about 24 kilometres from Brandon Road. However, this is not a fertile population.
Carp schools seem to have slowed down and "creeped forward" – as Schönnon describes how carp are now migrating. He attributed it to the results of unstructured activity efforts within the Mississippi River Basin. Now, it buys time for USACE to build the barrier.
The translation has been partially abridged.
Source: Research Circle (ID: keyanquan)
Written by Tom Johnson Translated by Akin Editor: Han Li
Original link: https://undark.org/2023/06/12/inside-the-race-to-build-a-1-2-billion-fish-barricade/