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This story comes from our partners at Ohio Valley ReSource, a regional journalism collaborative reporting on economic and social change in Kentucky, Ohio and West Virginia.

The variety of fish species in the Ohio River has substantially increased since the 1960s, according to a new study.

A team of researchers from Ball State University and Virginia Tech examined almost 60 years of fish surveys collected by the Ohio River Valley Water Sanitation Commission, or ORSANCO.

LISTEN: “Fish Species in Ohio River Have Substantially Increased Since ’60s, Study Finds”

The analysis, published last week in the journal PLOS ONE, examined ORSANCO-collected data from 1957-2014, as well as information on how land use near the river has changed over that time. Researchers found the number of species in the river varied from 31 to 90 each year, and increased over the decades studied.

Following the passage of the Clean Water Act in the 1970s, the data showed more fish species variety in the Ohio River, said Ball State Biology Professor Mark Pyron, lead author of the study.

“I think that the overall positive attribute now is we know that the Clean Water Act had a really positive impact on the fishes in the river,” he said. “Maintaining water pollution standards, and controlling input of toxins to the river, is going to have a huge impact in the future on controlling or maintaining water quality and quality of life.”

He added this trend is observed at most rivers in the U.S. where long-term datasets on fish species or river quality exist.

While generally the variety of fish species in the Ohio River trended upward over time, Pyron also said the data showed the trend was not observed across all species. For example, benthic invertivores or insect-eating fish in the Wabash River, which runs through Ohio and Indiana, have increased according to similar data Pyron analyzed.

They was not observed in the Ohio, he said. In fact, they slightly declined.

The study also examined land use changes surrounding the Ohio River over the last 60 years. In general, the researchers found agriculture near the river has decreased, forested land increased and some dams have been modified — changes that have likely positively impacted fishes in the river, Pyron said.

He noted the study used high-level data and so the findings were largely correlations. Pyron said more research is needed to tease out what is impacting specific species across the river’s 981 mile stretch. Next, he hopes to examine changes upstream and downstream and changes in body size of fish species.

Jason DeBoer, an ecologist with the Illinois Natural History Survey who studies large river fisheries, said in an email that the findings were interesting and largely mirrored those from other rivers in the Midwest, although few have seen a decrease in agriculture near their banks like the Ohio River has.

However, DeBoer, who was not involved in the study, said the significance of the findings — a threefold increase in fish species as water pollution decreased and water quality improved — should not be understated.

“Importantly, the ‘splash’ of findings like these sends ripples far beyond river scientists in the Ohio River basin,” he said. He noted they should be important to politicians and state agencies that pass and implement water quality laws as well as to industries and residents that share resources from the Ohio River.

“These findings are important to other river scientists around the country or the globe, who may not have a 60-year data set like this, but who are inspired to form partnerships with sanitary districts or other water/sanitation management agencies that might,” he added.

Pyron said having access to ORSANCO’s long-term monitoring data was crucial to completing this first analysis.

“If you don’t have long-term databases like this, where people have collected the same data over a long period of time from the same location, you can’t ask questions about whether things are changing or not,” he said. “You can’t ask whether there’s some impact of [the] activities that we’ve done. The only way to ask those questions is to have those long term datasets. So, we need to maintain ORSANCO for example collecting these data into the future so we know what’s going on with our ecosystems.”

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