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Fish Diversity Making A Comeback In The Ohio River

The planet is facing some hard times. Species diversity is plummeting and climate change is accelerating, but a new study indicates just how fast nature can bounce back when the right conditions are in place.

The Ohio River is once again teeming with fish diversity thanks in part to environmental regulations, said Mark Pyron, the study’s lead author and biology professor at Ball State University.

The 57-year review of fish surveys published in April found that species richness has gradually increased over the decades, likely due to ecological improvements following the Clean Water Act, Pyron said.

“So some of the lowest years, they got 31 species total and that’s bounced around a lot, to currently we are getting around 90 species per year,” Pyron said.

Prior to the Clean Water Act of 1972, industry could basically dump waste into the Ohio River with abandon, while runoff from agriculture pumped the river with excess nutrients, herbicides and pesticides.

Pyron said the federal and state regulations adopted in the wake of the Clean Water Act have helped control pollution in the river, reduced agriculture along its edge and even restored forest cover.

That forest in turn limits excess runoff and provides the right kind of nutrition to build a healthy river ecosystem. For example, the leaves that fall off the trees provide food for bugs, which are in turn eaten by the fish, he said.

But there are also other ways that man appears to have played a role in the success of certain fish species that swim in the river, Pyron said.

Pyron hypothesizes that species that eat other fish, like walleye, some sunfish and largemouth bass are doing better in the river.

“My guess is that’s because the dams are holding back water and its becoming more like lake conditions,” Pyron said.

All of that diversity helps build an ecosystem’s resilience so when one or two species go extinct, it limits cascading effects on the entire system.

“If you lose one or two of those it’s not going to be as important because your ecosystem functions will still be maintained,” Pyron said.

Of course there is still a lot of pollution flowing into the Ohio River. It’s coming from coal-fired power plants, industry, sewers, the occasional Superfund site… and trash.

As a result, humankind doesn’t really know how much better it could be because we don’t have the historical data to compare it to a time when the Ohio River was untouched by modern industry, he said.

“I think the only way we are going to know that is if we really cut it down to minimal [levels], or as low of levels of pollution as we can so we can kind of get a picture of what would happen to the ecosystem without that pollution,” Pyron said.

The historical data Pyron used came from the Ohio River Valley Water Sanitation Commission known as ORSANCO. Pyron noted that without it, he would not have been able to conduct his research.

ORSANCO’s Executive Director Richard Harrison said that Pyron’s research fulfills a core mission of the group.

"ORSANCO is pleased to see that the data from ORSANCO’s robust Ohio River monitoring programs is being utilized by stakeholders.  This data is made available to the public on the ORSANCO website and represents decades of monitoring conducted by ORSANCO’s scientists," Harrison said via email.

Ryan Van Velzer is the Kentucky Public Radio Managing Editor. Email Ryan at rvanvelzer@lpm.org.

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