Forget the recession — the biggest threat to the American economy could be an attack of giant Asian carp.
Ugly, pushy and always hungry, these 100lb (45kg) beasts are evading the high-tech electrical defenses that are supposed to stop them from swimming from the Mississippi River into the Great Lakes on the US border with Canada.
The result could be an underwater bloodbath, as the carp munch their way through entire species of rival fish and devour 40 per cent of their body weight in plankton every day.
Officials in the state of Illinois, who have taken to dumping poison in commercial waterways as a last resort, fear that the attack could lead not only to an ecological disaster but also to the collapse of the lakes’ $7 billion-a-year (£4.2 billion) fishing industry.
It gets worse: the only way to stop the killer carp, say environmentalists, is to close down the locks that connect the Mississippi to the Great Lakes — a move that could devastate the shipping industry and push up prices of iron ore, coal, grain and other goods.
“The impact is going to be large,” said Lynn Munch, a senior vice- president of the American Waterways Operators, which represents the US tug and barge industry. “It could definitely impact day-to-day living.”
The Governor of Michigan, Jennifer Granholm, has threatened to bring in the US Army Corps of Engineers to shut three locks near Chicago amid evidence that the carp are about to enter the lakes. Environmental groups are arguing that the Mississippi and the lakes should be separated permanently to ensure that any damage is contained. That, however, is not likely to happen any time soon. Colonel Vincent Quarles, the commander of the US Army Corps’ Chicago district, said this week that his agency was considering all options, but that it would not close the locks without first studying the possible effects.
The carp, known for leaping out of the water as boats pass by, were originally imported from Asia by fish farms in the southern states. They escaped into the Mississippi after severe flooding in the 1990s and have been travelling north every since.
Now they have reached the northern tip of the 250-mile (400km) network of rivers and canals that were built to connect the Mississippi and the Great Lakes a century ago. Tens of millions of tonnes of goods, including salt, sugar, molasses, cement, scrap metal and petrol, are moved annually along the canals or through the locks that lead into Lake Michigan. Any disruption could cost the US economy billions of dollars.
A non-lethal electrical barrier is supposed to stop the fish from moving any farther north. Occasionally the barrier has to be switched off for maintenance — leading to the recent strategy of dumping a toxin known as Rotenone into the Chicago Sanitary and Ship Canal near Lockport, Illinois.
After the poison has been given time to work US Coast Guard crews use large cranes with nets to scoop up the dead fish — as much as 2,000lb of them — before taking them to a landfill site.
Although no carp have yet been caught in Lake Michigan, DNA from the species has been found beyond the electrical barrier.
“This is an immediate threat to the Great Lakes, to our sport and commercial fishery and requires some emergency actions appropriate to the level of that threat,” Ken DeBeaussaert, the director of Michigan’s Office of the Great Lakes, said. “Closing the locks ... is an appropriate response.”
Other Big Fish in Small Ponds
— The voracious Nile perch, which can weigh up to 440lb (200kg), was introduced to Lake Victoria in the 1950s, causing the extinction or near extinction of more than 200 native fish species
— Zebra mussels arrived in the US Great Lakes in the ballast tanks of ships from Europe in the late 1980s. They have spread as far as New England, starving other species by eating huge quantities of algae
— Gambusia holbrooki, known as the plague minnow, was introduced to Australia in 1925 to control mosquitoes. It failed to do this, but instead quickly spread, eating frogspawn, attacking native frogs and preying on other fish
— The invasive northern snakehead — a fish with big teeth that can survive out of water — made national headlines in America when it was found to be breeding in a Maryland pond. Examples have since been found in Arkansas, North Carolina, and New York.