The project’s goals are to enhance and/or develop new barriers using carbon dioxide to deter the range expansion of invasive bigheaded carp. These fish continue to migrate northward and present a danger to Minnesota’s aquatic habitat. The locks and dams on the Mississippi River present strategic bottlenecks where non physical deterrents can be deployed to prevent upstream carp migration.
Acoustic deterrents have shown promise but are not completely effective. Two different strategies will be examined simultaneously to increase the effectiveness of acoustic deterrents by augmenting them with carbon dioxide. Bigheaded carp display strong aversion to the gas and, if successful, the combination of sound and carbon dioxide will increase the effectiveness of acoustic deterrents. The first objective will augment a bioacoustics bubble barrier by injecting carbon dioxide into the sound/bubble curtain. The second objective with use acoustic conditioning to train the fish to associate sound with carbon dioxide, which will prolong the fish’s aversion to broadband sound while simultaneously decreasing the frequency of carbon dioxide application. Both objectives are targeted to be deployed at the downstream lock gate at dams on the Mississippi River.
The fish behavior shuttle box has been constructed and sound and carbon dioxide conditioning trials were initiated this fall. The larger shuttle tank manufacture was delayed by the pandemic but has arrived and will be assembled in the near future. Sound mapping has been completed in the shuttle box and sound pressure levels have been calibrated. The fish tracking software has been installed and which allows fish position and swimming speeds to be calibrated.
Single day conditioning (three exposures in one day) and lower intensity pure tone stimulus seemed to have marginally effects on fish displacement and deterrent. Preliminary results of extended conditioning (2 to 3 days) and increased sound intensities (~125 dB) have greatly increased deterrence and will be the standard from this point forward.
Dr. Brooke Vetter, a recent hire at St. Thomas University has been assisting with the project at no cost to the grant. The experiments have provided training opportunities for four of her undergraduates students to date. Training has been provided for two graduate students.
The pandemic continues to present a challenge as there have been significant delays in acquiring parts and supplies. Additionally, the smaller speakers purchased for the shuttle box failed numerous times and delays were sustained in finding a new vendor that had miniature speakers in stock.