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Electrical Barrier To Keep Asian Carp Out Of Great Lakes
A permanent electrical barrier will go into use in February to protect the Great Lakes from Asian carp that are moving up the Mississippi river. The Chicago Sanitary and Ship Canal Dispersal Barrier stretches two rows of electrodes across the canal (approximately 220 feet apart) to create an Asian carp fence. The electrodes pulse direct current into the water; this causes the fish to turn back rather than pass through the electric current.
(From Schematic Diagram of Chicago San-Ship Canal Barrier)
Asian carp (bighead and silver) were imported by catfish farmers in the south in the 1970's to remove algae and suspended matter out of their ponds. Floods in the 1990's caused many of these farms to overflow their banks; Asian carp were released into the Mississippi River basin. They are voracious eaters and reproduce rapidly; they out-compete native fish that are used by people along the river. They grow up to four feet in length, weighing 100 pounds; they are the most abundant species in some areas of the river. Ecologists fear that they could become a dominant species in the Great Lakes.
(From Asian carp may grow to 100 pounds)
The electrical barrier will cost $9.1 million; 75% is paid from federal funds. It will cost about $500,000 per year to operate. About thirty barges per day pass through the canal.
SF author Roger Zelazny wrote a series of stories published as My Name is Legion in 1976. One of them is set in a marine park in Florida. The park is divided into four separate areas by sonic curtains, which are described as a "sound barrier" that protects the species in the park. Each sonic curtain is controlled by a switches on the bottom; in an unusual touch, dolphins in the park teach each other how to use the controls so they can move freely.
Sonic curtains are similar to a known behavior of humpback whales called bubble feeding. Humpback whales blow air from blow holes while slowly spiraling to the surface; the sound and bubbles concentrate their small prey in a small area. The whales then swim through this narrow spiral, gulping their prey more efficiently.
For another example of an adjustable animal barrier, see the sonobarrier from Frank Herbert's 1977 novel The Dosadi Experiment. Read more about the Asian Carp Fence.
Scroll down for more stories in the same category. (Story submitted 1/13/2005)
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