OSU researchers using sound technology to study fish populations

Oklahoma State University Ag Research experts are studying the population size of shad fish in Arkansas reservoirs to help maintain bass fishing for anglers.

OSU graduate student Joe Dittmer and Dan Shoup, professor in the OSU Department of Natural Resource Ecology and Management, are using hydroacoustics technology to sample shad populations, which are small schooling fish that travel in packs and serve as a primary food source for temperate bass.

Hydroacoustics is the study of sound waves in water. These sound waves can provide researchers valuable information. In this case, they are determining the size of shad populations to evaluate the bass’ food supply.

Fishing has a large economic impact in the U.S. According to the American Sportfishing Association, U.S. anglers have an economic output of $148 billion annually with Oklahoma contributing $2.5 billion and Arkansas generating $1.2 billion. Sean Lusk, a biologist with the Arkansas Game and Fish Commission, said that in 2017, there were an estimated 267,352 licensed resident anglers in Arkansas with a top three preference for black bass. These anglers have invested nearly $3 billion in their fishing and boating equipment. Oklahoma anglers also travel into Arkansas to bass fish.

“Historically, managing the predator-to-prey ratio in large reservoirs has been very reactive,” Lusk said. “By the time biologists identify there are too many predators and not enough prey, it is difficult to implement any action that can quickly restore the proper ratio. Hydroacoustics gives us the ability to better predict an imbalance and adjust management strategies to protect the prey population.”

Through his research, Dittmer shoots sound into the water then measures how long it takes and at what volume the sound returns. This shows researchers how far away an object is and how big or small it is — a large fish will likely give off a stronger, louder sound than a small fish.

“To some extent, we can even characterize what produced the echo,” Shoup said. “We can take that time delay and measure the distance the object is from the hydroacoustics technology.”

Arkansas Game and Fish officials stock temperate bass in their reservoirs, Dittmer said, because the fish do not reproduce on their own in most freshwater reservoirs. Measuring the bass’ food source indicates how many bass a reservoir can support.

“Accurately sampling shad with traditional methods would take a lot of time, and you don’t necessarily get a true representation of what’s actually there,” Dittmer said.

With hydroacoustics, researchers can cover the entire lake uniformly and at a faster pace. It also gives a precise estimate of population size.

“Arkansas Game and Fish needed someone who could help deal with design issues and develop a protocol to measure shad populations the same way every time,” Shoup said.

Dittmer also uses imaging sonar, which is a sonogram-type technology, to see the shad.

“The imaging sonar gave me a good method of tracking how the fish react to the boat, and I can more confidently measure what species of fish my samples are,” he said. “Our research centers around whether we can get better data during the day but also trying to tackle the problems that come with daytime data.”

Their research found that sampling shad during the day rather than at night gives a more accurate population estimate. The OSU researchers hope to soon develop a standard sampling method and set a hydroacoustic protocol that can be implemented on lakes across Arkansas.

“It will be an essential tool in making informed management decisions,” Lusk said.