Asian carp barrier


There may be an inexpensive and ‘sound’ way to stop Asian carp

By Ted Pennekamp


A new method has now been developed that could help slow down the advance of invasive Asian carp working their way up the Upper Mississippi River. Recently, Bighead and Silver carp eggs and late-stage embryos have been found near Lynxville in Pool 10. Evidence of Asian carp has been found as high up as Lock and Dam 2.

A number of methods have been researched and some have been deployed, such as electronic barriers, in order to stop the carp. 

Now, University of Minnesota professor Peter Sorensen and researcher Dan Zielinski say they can create sound and bubble barriers to divert Asian carp. They hope to receive $60,000 in funding to order and install five speakers to repel carp at Lock and Dam 8 at Genoa, Wis.

Sorensen said the sound (which imitates boat motors) irritates and repels Asian carp, which are more sound-sensitive than other fish species. In fact, it’s the sound of motors that make silver carp leap high into the air, and thus become a hazard to boaters. Catfish are the only other fish that seems to be affected by the sound generated by Sorensen’s speakers. 

Asian carp are successfully breeding below the dam, but there’s no evidence they are breeding above it in Pool 8, which extends north along the Minnesota-Wisconsin border to La Crosse. Sorensen and his team would play those sounds just downstream of the lock, which is the carp’s most likely doorway farther upstream.

The goal is to design a deflector shield around the lock. Time is crucial because bighead and silver carp swim upstream to spawn, and spawning will begin this summer.

The plan is based upon Asian carp’s vulnerabilities: a sensitivity to sound and an inability to swim fast. A carp’s “hearing” is 10 to 100 times more acute than that of all native fish, except catfish, because of a rib bone that vibrates against its swim bladder, essentially turning the organ into a large eardrum.

The underwater sound barrier would protect the lock. In addition, because of the carp’s relatively slow swimming ability, if the U.S. Army Corps of Engineers can keep water flowing fast enough through the dam’s gates, the carp could not swim through.

The sound barrier, along with fast flowing water, is not expected to be 100 percent effective, but above 90 percent is considered realistic. Such a barrier could prevent Asian carp from establishing themselves as a breeding population and could be effective for many years. 

The underwater speakers and the changes in the dam’s gate procedures need approval from the Army Corps of Engineers. Neither the speakers nor the gate procedures would be a hindrance to navigation or the structure of the lock and dam.

It will cost $45,000 to obtain the speakers and $15,000 to deploy them. Sorensen and this team are still looking for the funding, however. 

Asian carp are a grave concern because they can aggressively compete with native commercial and sport fish for food and can potentially disrupt entire ecosystems. Also, silver carp can injure boaters when the fish leap out of the water. 

A couple of summers ago, the Wisconsin Department of Natural Resources announced the discovery of Asian carp in the Wisconsin River below the Prairie du Sac Dam, and the discovery of Asian carp DNA in the St. Croix River.

Individual adult fish have been found on occasion at various locations in the Wisconsin waters of the Mississippi River in recent years. In the Southwest Wisconsin area, a silver carp was found in February of 2011 near Ferryville. Bighead carp were also found by commercial fishermen near Ferryville in 2002 and 2009. A bighead carp was found near Glen Haven in 2009. 

Research biologists such as U.S. Geological Survey Supervisory Biologist Mark Gaikowski have said that the possibility for Asian carp to become the dominant fish by numbers and biomass certainly exists within many aquatic systems. For bighead carp and silver carp, the primary threat they pose is the over-consumption of plankton, algae and zooplankton, which serves as food for native invertebrates (themselves important food) and plankton-eating native fishes including adult bigmouth buffalo, gizzard shad, and paddlefish, and all native fishes at larval stages. Game fish species then tend to disappear from the area due to a lack of prey fish.

There are several control tools that are being evaluated, including:

•the capture of control agents in microparticles to control bighead and silver carp. These particle “bio-bullets” stick in the more mucous gills and mouths of Asian carp while passing through the mouths and gills of all other species, thus leaving the other species unharmed. Gaikowski and Jon Amberg of the USGS in La Crosse have worked on these poison pill bio-bullets since 2009. 

•algal feeding attractants to attract fish to locations where they could be removed.

•new control agents, including fish pathogens to which the carp may be susceptible.

•Judas-fish—using radio-tagged carp that could identify where carp are aggregating.

Gaikowski has also said there are several barriers that are being evaluated including:

•the use of water guns that create underwater pulses of sound and pressure that deter fish.

•the use of carbon dioxide as a chemical barrier to fish.

An electrical barrier system is presently used to prevent bighead carp and silver carp from entering the Great Lakes through the Chicago Area Waterway System. This and other electronic barriers have not been altogether successful, and numerous carp are getting through.

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