The electric barrier in the Chicago Sanitary and Ship Canal may effectively prevent Asian carp from entering Lake Michigan, according to preliminary research results. In the early stages of an Illinois-Indiana Sea Grant-funded study, researchers found that more than 99 percent of bighead carp were deterred by a simulated electric barrier modeled after the actual one. Using fish raceways to do controlled experiments, John Chick and Mark Pegg of the Illinois Natural History Survey are testing the potential effectiveness of the present electric barrier, as well as exploring additional barrier technologies as they relate to Asian carp. Two species of Asian carp, bighead and silver, are migrating closer to the actual barrier site, located near Romeoville, Illinois, and have been spotted as close as 25 miles from Lake Michigan.
Thus far in the study, there were 381 attempts by bighead carp to pass through the simulated barrier--379 times the fish turned around. Only one fish went through the barrier, and in fact, did it twice.
"This was a smaller carp, which was not surprising. Smaller fish are less susceptible to the electric current," said Pegg. These tests were done for six continuous hours per day for three days.
Asian carp, which have grown to 50 pounds in U.S. waters, were brought here for use in aquaculture in the 1970s, and escaped into the Upper Mississippi River System. The populations of these species have increased dramatically in some areas.
"Asian carp consume zooplankton, which all fishes typically feed on in their juvenile stages, so they have the potential to adversely affect every species of fish in the Mississippi River and Great Lakes," said Pegg.
The electric barrier was turned on in April in an effort to stop non-native fish from moving between the Great Lakes and the Mississippi River basin. The idea is that as fish pass through the barrier, they feel increasing levels of electricity, which leads them to turn around. "Because the 60-feet wide barrier is not as strong higher up in the water column where Asian carp are typically found, there has been some concern that the electric field may not effectively repel the fish," said Pegg.
Recently, the International Joint Commission has recommended that a second barrier be installed as a backup to ensure that the carp and any other invasive fish species are stopped. And, Chicago Mayor Richard Daley has asked Congress for funding to strengthen the electric barrier and to study ways to keep invasive species from entering the Great Lakes.
Next, Chick and Pegg will explore different scenarios using the present electric barrier technology, varying the strength and width of the electric pulse within the recommended safety guidelines. They will also experiment with other barrier methods including "fish guidance systems" that use sound and a "wall of bubbles." "We will test the effectiveness of these technologies and then try them in combination. Perhaps the fish can become used to one or the other, but in combination, they may prove successful," added Pegg. They will also test the effectiveness of these technologies in augmenting the electric barrier.
Carp have been migrating on their own towards Lake Michigan, but there is also a risk that anglers and others who harvest and fish with wild bait may inadvertently transport these species. "When minnows are harvested for bait, smaller or newly-hatched carp may tag along," explained Pegg.
There are precautions that anglers can take to reduce the risk of spreading exotic species, such as the Asian carp. "Never dispose of your bait by putting it into a waterbody," said Pat Charlebois, Illinois-Indiana Sea Grant biological resource specialist. "Throw unused bait away on land or in the trash."
If you are fishing with wild bait, use it on the water body from which it was collected. And you can also learn to identify Asian carp.
The National Sea Grant College Program is a consortium of 30 state university-based research and outreach programs. Created by Congress in 1966, Sea Grant combines university, government, business and industry expertise to address coastal and Great Lakes needs. Funding and administrative support is provided by NOAA.
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