Asian silver carp

Asian Sliver Carp

Alfredo Meza

Effect on people

Invasions are nothing new for the Great Lakes, where at least 136 of the wildest species already live, ranging from zebra mussels. Still, the looming attack from Asian carp big, hungry goldfish relatives has been stirring up widespread concern, especially since the first traces of Asian carp DNA were found in Lake Michigan late last year. The encroaching carp have made national and international headlines, sparked a legal fight among states, and earned nearly $80 million in aid from the U.S. government.

The effect on people that the silver carp had was that an army of Asian carp is itching to invade new waters again, barely taking a breather after its three decade conquest of the Mississippi River Basin. The ambitious foreign fish are still multiplying even as they deplete native food supplies, and now they're eyeing their biggest prize yet the Great Lakes, Earth's largest freshwater ecosystem.

The silver carp is also called the flying carp for its tendency to leap from the water when

startled. They can grow to over 40 lb (18 kg),

and can leap 10 ft (3 m) in the air. Many boaters traveling in uncovered high-speed watercraft have been injured by running into the fish

while at speed. In 2003 a woman jet-skiing broke her nose and a vertebra

colliding with a silver carp and nearly

drowned. In another example, a teenager's jaw was broken by a

silver carp while being pulled on an inner tube.

Water skiing in areas where silver carp are present is extremely

dangerous.

Asian silver carp

The Asian silver carp is a species that is a fresh water cyprinid fish a variety of Asian carp native to north and northeast Asia. It is cultivated in China. Pound for pound, more silver carp are produced worldwide in aquaculture that Silver carp were imported to North America in the 1970s to control algae growth in aquaculture and municipal wastewater treatment facilities. They escaped from captivity soon after their importation. They are considered a highly invasive species. Silver carp together with the closely related bighead carp often reach extremely high population densities and are thought to have undesirable effects on the environment and on native species.

By 2003 silver carp had spread into the Mississippi, Illinois, Ohio, and Missouri rivers and many of their tributaries in the US. They are now abundant in the Mississippi River watershed from Louisiana to South Dakota and Illinois, and are close to invading the Great Lakes via the Chicago Sanitary and Ship Canal. Navigation dams on the Mississippi River seem to have slowed their advance up the Mississippi River, and until November 2008 silver carp had not been captured north of central Iowa on the Mississippi. Dams that do not have navigation locks are complete barriers to upstream natural movement of silver carp, and it is important that fishermen do not assist this movement by the unintentional use of silver carp as bait.

Silver carp are thought to feed

largely on phytoplankton, they

also consume zooplankton and

detritus. Because of their plankton-feeding

habits, there is concern that they will compete with native planktivorous fishes,

which in North America include

paddlefish Polyodon spathula, gizzard shad Doro soma cepedianum, and

young fish of almost all species.

Because they feed on plankton, they are sometimes successfully used as methods for controlling water quality, especially in the

control of noxious cyanobacteria (blue-green algae). However,

these efforts are sometimes not successful. Certain species of blue-green algae, notably the

often toxic Microcystis, can pass through the gut of silver carp

unharmed, and pick up nutrients while in the gut. Thus, in some cases blue-green algae blooms

have been exacerbated by silver carp. Also, Microcystis has been shown to produce more toxins in

the presence of silver carp. Silver carp, which have natural defenses to the toxins produced by blue-green algae, sometimes can contain enough algal toxins

in their systems that they become hazardous to eat.

Introduced in the 70s, most likely another Arkansas fish-farm escape, silver carp are now legendary across the country's midsection for launching themselves into the air when startled, often at the sound of motorboats .The largest silver carp on record weighed 110 pounds, but even 20-pounders are dangerous during their forceful leaps, which can injure any people on the water. If you're a skier, you can't ski where silver carp are abundant. That just wouldn't be smart, people says. And if you're going to be around these fish, you need to protect the boat's throttle. They can break lots of things in a boat, but if they break your throttle or knock it into gear, that's a big problem." But black eyes and boat crashes aren't the only threats from silver carp their main food is phytoplankton, the tiny algae that larval fish and mussels need to survive.