Invasive carp, most notably Bighead carp (Hypophthalmichthys nobilis) and Silver carp (H. molitrix), were introduced to control weed growth in aquatic farms located on the Mississippi in the 1970s, and some escaped during later flooding. They rapidly established within the river and starting expanding northwards up the Mississippi River and its tributaries.

Bighead, silver, black and grass carp are known to out-compete native fish for food and space. They are now present in the Mississippi River and also the Illinois, Missouri, Ohio, and Wabash rivers and their tributaries.

Increasing concern was expressed as the carp migrated up the Illinois River and towards the Chicago Sanitary and Ship Canal that links the Illinois River with Lake Michigan, with the potential threat to the Great Lakes $7 billion peryear fishing industry. In order to manage the invasive species, a number of technologies have been considered and safety and reliability issues associated with the electric barrier located on the Chicago shipping canal increased interest in Fish Guidance’s systems.

Initial trails were carried out by Illinois Natural History Survey (INHS) in 2003, when a BAFF was installed in a hatchery raceway and the system was assessed to determine its ability to preventing Bighead carp from crossing the barrier. The testing demonstrated a 95% deflection efficiency when a higher frequency signal way used.

Following the successful trial the Minnesota Department of Natural Resources (DNR) funded FGS to measure the audiograms for the Silver carp and Bighead carp in order that an optimised barrier could be specified for the Chicago Shipping Canal and the audiograms were completed in 2004.

A review on behalf of the Minnesota DNR of all available technologies to limit the invasion of invasive species into the Upper Mississippi River Basin was published in 2004 and concluded ‘that an acoustic deterrent such as a Sound Projector Array (SPA) based acoustic bubble curtain (SPA/BAFF) downstream of a lock entrance location’….would provide ‘the most feasible opportunity to limit or slow the upstream invasion’ of these carp.

Interest in FGS’s acoustic technology continued and INHS proposed a series of in-situ field tests at its Quiver Creek Biological Research Station near Havana, Illinois. Quiver Creek is a tributary of the Illinois River, already populated by invasive carp and effectively blocked upstream of the field station by a low head dam. As a result it offered an ideal test site.

The creek is approximately 16m wide, with a flow of 0.4-0.8m/s. It was proposed to install a barrier across the width of the creek and assess the number of fish that pass through the barrier.

FGS was asked to provide a suitable system and a 16m wide combined acoustic and High Intensity Light based BAFF system was supplied. The system utilised FGS’s MkII 15- 100 Sound Projectors, which were considered better suited to the site than the more powerful 30-600 Sound Projectors that would be used in a larger permanent system. The Signal Generator was supplied with a signal developed during the earlier testing of the system by the Illinois Natural History Survey, and optimised following the audiogram testing.

The barrier was evaluated by electrofishing the 200m stretch of the creek between the barrier and the upstream dam and removing all of the fish, tagging them, and releasing them downstream of the barrier. Bighead and Silver carp were also captured in the main Illinois River, tagged and transferred to immediately downstream of the barrier.

The system was initially assessed in 2009, and a more detailed assessment was carried out in 2010. During the preliminary testing of the barrier in August 2009 the research staff observed a number of Silver carp jumping out of the water and away from the barrier and concluded that this was in response to the Silver carp challenging and being repelled by the barrier. The main method of evaluating the performance of the barrier was the recapture of tagged fish upstream of the barrier, following repeated electrofishing of the area between the barrier and the dam. A number of different operating conditions were evaluated, including running with the High Intensity Lights off and also permanently on.

The 2009 results demonstrated 100% deflection of the Silver Carp, with no Silver carp being found upstream of the barrier. In 2010 both Silver carp and Bighead carp were assessed, and no Bighead carp were found upstream of the barrier. Two Silver carp were found about the barrier, resulting in the following deflection efficiencies –

Bighead carp (Hypophthalmichthys nobilis) 100%

Silver carp (Hypophthalmichthys molitrix) 99.7%

As part of the trial the researchers also assessed the deflection efficiency of the barrier on a range of other fish, and the overall deflection efficiency for the main named species, excluding bighead and silver carp, were:

All non-bighead and silver carp species 97% 

Gizzard Shad (Dorosoma cepedianum) 100%

Walleye (Sander vitreus) 100%

White Bass (Morone chrysops) 100%

Largemouth Bass (Micropterus salmoides) 97.8%

Bluegill (Lepomis macrochirus) 97.4%

Grass carp (Ctenopharyngodon idella) 96.6%

Green sunfish (Lepomis cyanellus) 96.2%

Percids 96.0%

Common carp (Cyprinus carpio) 91.3%

Observations throughout the trial period also noted that even though the fish were held back by the barrier, the local beavers were happy to pass through the barrier and it did not affect their movement along the creek.

The research concluded that the BAFF system would be a suitable method of reducing the ability of invasive carp to move into areas not already colonised, which would reduce the probability of these species reaching the Great Lakes. It also proposed the use of the system to herd the carp below locks and dams, where the fish can be present in high densities, so that they can be harvested and removed from the ecosystem. Lastly it was proposed a BAFF based barrier be located below the existing electric barrier to help reduce the number of invasive carp that are challenging that system.

For a copy of the independent trials, or the independent review recommending the use of the BAFF technology in the fight against invasive species, please contact FGS.