Impact of Asian carp on the Great Lakes
From: Â http://www.freep.com/article/20100126/NEWS06/100126010/1322/Impact-of-Asian-carp-on-the-Great-Lakes
If Asian carp establish a breeding population, they could hurt the Great Lakes by outcompeting other species, as has happened on rivers in the South, where some stretches of river are mostly Asian carp. They could alter the ecosystem by filtering out food that other fish and smaller organisms need, and theyâ€™re dangerous to boaters and anglers because of their size and weight.
Recreation and fishing could be forever changed.
Silver carp (Hypophthalmichthys molitrix)
â€˘ Up to 4 feet long and 40 pounds.
â€˘ Found in 12 states, including evidence of reproducing population in Louisiana and in the Mississippi River.
Bighead carp (Hypophthalmichthys nobilis)
â€˘ Up to 4 feet long and 80 pounds.
â€˘ Reported in open waters by early 1980s, they are found in 18 states.
JUMPING DANGER: Silver carp will torpedo out of the water up to 10 feet in the air when agitated and can cause serious injury to boaters or anglers.
COMPETITION FOR FOOD: The carpâ€™s only food is plankton. In large numbers, they could deplete plankton that native fish depend on.
ADAPTATION: Bighead and silver carp tend to grow big and produce a large number of offspring.
BARRIER CONTROLS: Bubble curtains deter fish without impeding boat traffic. The screen is a steady stream of bubbles being generated via a submerged perforated tube through which compressed air is released. The wall of released bubbles is used to guide approaching fish into a by-wash. Bubble curtains can achieve greater efficiency when combined with other deterrent systems such as sound or light.
COMMERCIAL USE: Asian carp were introduced to the U.S. in the early â€™70s to control algae in catfish farms in the South. Floods washed them into the Mississippi River in the '80s. They've worked their way upriver ever since. They thrive in the Illinois River, a tributary of the Mississippi. The State of Louisiana has approved plans to market the fish to restaurants and fish stores. Asian carp will be sold as silverfin â€” a more appealing name.
KILL THEM WITH POISON OR ELECTRIC CURRENT: The Army Corps of Engineers is updating an electric field designed to repel invasive fish species from entering the Great Lakes. Once complete, two nonlethal dispersal fields are expected to replace the aging system.
1. Creates a 2-volts-per-inch electric field in the water, discouraging fish from swimming onward.
2. Once complete, this field will work concurrently with the first one to create a much larger grid to repel fish.
3. The original barrier emits a 1-volt-per-inch field and is to remain active until an upgrade is complete.
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