Carp-e Diem
An invasion of silver carp and bighead carp could be disastrous for the Great Lakes. Natural fish stocks - pickerel, bass, trout and the rest - could wither and die; recreational boating - even waterskiing and tubing - could become dangerous! Can you imagine wearing a motorcycle helmet and visor to go for a spin in your bow-rider? According to some, it could happen.
How did the carp get here?
Asian carp are voracious consumers of plankton, so they do a bang-up job cleaning up the algae in aquaculture ponds and sewage treatment facilities. Catfish farmers and others brought them to the Louisiana area in the 1970s. They escaped into the Mississippi during the floods of the 1990s and have been working their way upriver ever since. Now they are within a few miles of Lake Michigan.
The Army Corps of Engineers tried to stop them.
A sophisticated - and expensive - electric barrier in the Chicago Sanitary and Ship Canal was supposed to stop the fishes’ progress by putting an electric charge in the water that would repel them. Unfortunately DNA tests of the water on the lake side of the barrier show the invaders have made their way past the gate and are now within a mile of the last lock. Many are pressuring to have the lock shut tight cutting off not only recreational boats but the myriad barges that make their way up and down the river.
Some bighead carp have been caught in Lake Erie, likely released from live fish markets. What some feel may be best for the fish is not the best thing for the local ecosystem.
Why are these Asian carp hazardous to health?
A large population of bighead and silver carp in the Great Lakes waters would add to the pressure of zebra mussels and take a bigger bite out of the plankton that is the first link in the chain of natural fish stocks. But the danger comes from the silver carp in particular. These fish quickly grow up to four feet long and can weigh 100 pounds. They also have the unfortunate habit of leaping out of the water when they are frightened. A passing boat… a skier or wakeboarder… a child on a tube could set one off. It has happened. A driver of a boat full of youngsters was knocked off his seat when a leaping carp hit him. Another carp leaped in front of a 15-year-old riding a tube behind a boat. It knocked him unconscious and broke his jaw.
All is not lost.
Biologist Duane Chapman is a US Geological Survey researcher who has extensively researched the fish on the heavily infested Missouri River. He says an infestation is all about numbers. For the carp to establish a breeding population in Lake Michigan, and from there to the other Great Lakes, the fish first need to find each other then have to find a place to spawn. He says Asian carp are not likely to spawn in open water. Fertilized eggs need long free-flowing rivers to hatch.
There are many rivers that fit the bill - particularly on the Canadian side of the Great Lakes. But enough fish have to get together to form breeding stocks and they have to find the right rivers. It could happen but it may not. In the meantime, efforts to keep the fish out of the lakes don’t have to be 100 percent successful to be effective. We just have to remain vigilant and do what we can to keep them in check.