Study: Variety of freshwater fish species has rapidly increased in the Ohio River since ‘60s

MUNCIE, Indiana –  The variety of freshwater fish species in the Ohio River has evolved dramatically since the 1960s, possibly due higher water quality and shifting in how the land is used, says a Ball State University researcher.

Mark Pyron, a Ball State biology professor, used 57 years of rotenone and electrofishing fish collection survey data (1957–2014), collected by the Ohio River Valley Water Sanitation Commission, to examine changes to freshwater fish in the Ohio River over this period. 

The study found the number of species richness varied from 31 to 90 each year, and increased over time. Changes in the fishes were correlated with the decrease in agriculture, an increase in forest, and modifications to hydrology from dams.

The environmental modifications were associated with more fish species which feed on plant matter and detritus, and fewer fish feeding on plankton and on other fish, Pyron said.

Long-term fish assemblages of the Ohio River: Altered trophic and life history strategies with hydrologic alterations and land use modifications,”  has been published by the open-access journal PLOS ONE. Pyron worked with faculty from Ball State and Virginia Tech University on the study.

The Ohio River Basin is a region of 204,000 square miles covering parts of 14 states and including a population of nearly 25 million people, many in such major cities as Pittsburgh, Columbus, Cincinnati, Louisville, Indianapolis, and Nashville.  The Ohio River flows 981 miles from Pittsburgh to Cairo, Illinois, where it dumps into the Mississippi River. The Ohio and its tributaries has 19 locks and dams.

The professor pointed out that the Ohio River Basin has seen dramatic changes since the arrival of European settlers, starting with movement from America’s East Coast in the in the late 1700s and early 1800s.

“The legacy of agriculture and land use is manifested in the Ohio River Basin, drastically modified via logging and wetland draining following European colonization,”  said. “After this period, the Ohio River Basin watershed was historically dominated by agriculture, and then converted from agriculture to forest during the 1960s-80s. The effects of these changes on fish throughout the basin are not fully known. 

Pyron said that future land use modifications, climate change, and altered biotic interactions could continue to contribute to complex patterns of change in freshwater fish assemblages in the Ohio River. 

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