When Dr. Christa Woodley, a research biologist with the U.S. Army Engineer Research and Development Center (ERDC), heard about the U.S. Geological Survey (USGS) study to control invasive Asian carp through acoustics, she was excited by the possibilities.
Led by USGS Research Fish Biologist Dr. Marybeth Brey, the multiagency team intends to deter the fish from moving further up the Mississippi River by broadcasting underwater sounds the researchers believe are intrusive only to the invasive carp, and the method will leave virtually no footprint on the environment.
“Whenever you put something in the water, you are usually going to have to pay a cost,” Woodley said. “But this is a win-win — the public should be very interested in any deterrent research that allows us to achieve our mission without damaging the environment.”
Silver carp, bighead carp, black carp and grass carp are the four types of Asian carp that pose a threat to the Great Lakes’ $7 billion fisheries; the invasive fish grow quickly and compete aggressively with native fish for food and habitat.
The sounds will be released from an underwater Acoustic Deterrent System (uADS) housed in a weldment ― a 105-foot-long beam with 16 speakers — in the approach channel of Lock and Dam 19 (LD19), located in Keokuk, Iowa.
“This is all new; it’s not a design that’s been used before and it’s never been recessed in a lock’s discharge lateral,” said Brey.
Designed by a team of 15 USGS and U.S. Army Corps of Engineers (USACE) personnel led by Kirk Sunderman, a USACE Rock Island District project engineer and project manager, the uADS was installed in the lock approach Feb. 3.
The study is a precursor to the Brandon Road Lock and Dam project, which has just commenced. Woodley will utilize the data collected by the study to evaluate the effectiveness of using the acoustic deterrent for that project.
“In the Brandon Road project, 90% of the lock is being cut out and rebuilt with deterrent systems; the acoustic system will be one of several types of deterrents,” she said.
What will the Asian carp hear that will cause them to avoid the area? Woodley compares some of the sounds to “an engine coming towards you,” others to the predators found in the fish’s home range — dolphins.
Woodley performed the acoustic research to isolate the sounds, and she describes how her work built on previous work completed by partners. “We do have some universities involved in the project that helped us with documenting the fish hearing; the University of Minnesota Duluth did quite a bit of that kind of work.”
“They’re the ones who said, ‘Asian carp can hear at this range and at these decibels,’” Woodley said. “I took that information and said, ‘OK, if this is the hearing range, then that allows me to create all sorts of sounds that are within this decibel range and frequency band for the fish to hear’ and then ERDC tested the sounds.”
Woodley observed the fish either stopped or turned around when they heard the sounds in the ERDC-Environmental Laboratory’s 10,000-gallon Cognitive Ecology and Ecohydraulics Research Facility. In the meantime, USGS researchers had collected laboratory and field data about the effects of a 100-horsepower boat motor playback on fish behavior, concluding that the boat motor and the playback of the boat motor showed potential for deterring invasive carp.
“I was able to take the 100-horsepower boat motor sound, and say, ‘OK, what part of this sound pattern makes the fish move away versus what part makes them comfortable to return?’” Woodley said.
She took that sound, and broke it down into 30 principal parts, and played each part back to the carp to find the exact components that were causing the fish to stop. Woodley then integrated those components into the sounds she had previously engineered, and the team had their sound vocabulary, based on multiple sources.
Now that the weldment has been successfully installed, the next major project milestone will be tagging the fish. The USGS team, led by Brey, will manage that portion of the study. “The idea is to put together an analysis that describes how long it took a fish to get through the deterrent or to turn around from the deterrent, to mark different types of behaviors that a fish might have in that lock approach, and compare those to when the sound is running and when the sound is off,” she said.
The study will last up to three years.