Invasive carp poses threat as a predator in the Great Lakes

by Angie Asam, Staff Writer

In the 1970s catfish farmers in the south imported two species of Asian carp, the silver and the bighead, to remove algae and suspended matter from their ponds. During floods in the early 1990s many of the ponds overflowed releasing the carp into local waterways in the Mississippi River basin.

Since the flooding they have steadily made their way north up the Mississippi and become the most abundant species in some areas of the river. In fact, according to Marc Gaden, a spokesman for the Great Lakes Fishery Commission (GLFC), in some places in the Mississippi the carp are making up 95 percent or more of the biomass. Asian carp have now been found in the Illinois River, which connects the Mississippi to Lake Michigan and essentially the entire Great Lakes system. The presence of the carp in the Illinois River is a cause for concern as the dangerous invasive species could enter the Great Lakes.

Asian carp are large, as they can weigh up to 100 pounds and grow longer than 4feet; they reproduce rapidly and consume vast amounts of food. As of right now the only thing separating the carp from Lake Michigan is the Chicago Sanitary and Ship Canal. In that canal an electrical fish barrier system is what is keeping the fish in the Illinois River.

?Interestingly enough what has been going on lately is that the Great Lakes Fishery Commission, state agencies, federal agencies, and many others have been working with the Army Corps of Engineers (Corps) to get an electrical barrier up and operational in that canal. It has been a long process and right now we have two of three barriers operational. They will all be one barrier system eventually but had to be built in sections,? said Gaden.

The Corps operates the system and is now trying to assess just how high of a voltage of electricity can be run through the barrier. According to Gaden the barrier was built to withstand a lot more power than what is currently being run through it. ?It is our hope that they will be able to turn the juice up and make the barrier system a stronger deterrent to fish passage,? said Gaden. Once the testing is done, those working on the barrier system will have a better handle on the situation and how much the barrier system is going to help stop the migration of fish to the Great Lakes ecosystem through that canal.

Is the barrier system the answer? According to Gaden the barrier system is not the end all or be all. ?No one has ever challenged that the barrier system will not completely solve the problem. However, it is absolutely critical because without it those fish would have an unimpeded pathway to Lake Michigan,? said Gaden.

The GLFC, the Corps and the Alliance for the Great Lakes have been talking about the bigger picture, what else can be done in that canal to make sure that the species would not have the chance to migrate between the Mississippi River basin and the Great Lakes. ?We want to bring the risk that they can enter the Great Lakes to zero,? said Gaden. A year ago the Alliance for the Great Lakes did a study on traffic flow to find if there were places the canal could be altered. Canals connecting the Great Lakes basin to other sources of water have served as one important way for aquatic invasive species to enter the Great Lakes; the other has been ballast water discharge from ocean going ships. The Chicago canal has already allowed several other damaging invasive species to enter the Great Lakes such as the zebra mussel and the round goby.

The study stated, ?The long-term approach to achieving protection is ecological separation. A true ecological separation is defined as no interbasin transfer of aquatic organisms via the Chicago waterway system at any time ? 100 percent effectiveness. Ecological separation prohibits the movement or interbasin transfer of aquatic organisms between the Mississippi and Great Lakes basins.?

The study concluded that the need for direct diversions of Lake Michigan water into the Chicago waterway system is diminishing and navigation is confined in bulk to specific portions of that system. According to Gaden the study was a stepping-stone or starting place as the Corps was authorized in legislation to do a major study of those same questions. ?The fact that the Corps was given the authority to do that is huge,? said Gaden.

Not only do the Asian carp quickly move, reproduce and eat a majority of the food, but they are dangerous to boaters as well. The silver carp leap out of the water and have struck boaters, skiers, tubers and others enjoying the water. ?They are like missiles with fins,? said Gaden. They have proven to be very dangerous in the Mississippi and would be just as dangerous in the Great Lakes.

The carp have little to no commercial value and would further hurt the ecosystem in the Great Lakes by killing off much of the native species. Right now the most dangerous invasive species in the Great Lakes is the sea lamprey, which can be controlled. Gaden believes that the Asian carp, if it makes its way to the Great Lakes, could have a significant impact on the entire ecosystem. Gaden said a new invasive species is introduced in the Great Lakes about every nine months and the on

ly one that can be controlled is the lamprey. Prevention rather than control becomes most important when dealing with aquatic invasive species.

?It is absolutely critical to keep the Asian carp out or they will be here to stay and have ongoing negative impacts on the entire Great Lakes ecosystem,? said Gaden. Although the efforts to construct the barrier and get it fully operational have taken several years the carp that were making their way up the river have not been moving as fast as they have in other parts, allowing the time for the barriers to be constructed as well as alternatives to be looked at.

Work will continue on the barriers in the Chicago Sanitary and Ship canal as preventing the carp from entering the Great Lakes is a major concern of many groups. The barriers will not be the entire answer but research will continue to be done to keep the aquatic invasive species out of Lake Michigan and out of the Great Lakes ecosystem.

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