Fish and bugs love low dam modification and removal

By Mike Ekberg, manager of water resources monitoring and analysis What if I told you the Great Miami River in Dayton has some of the healthiest populations of fish and macroinvertebrates (stream bugs) and provides some of the best aquatic habitat in Ohio? You probably wouldn't believe me. After all, urban rivers aren’t often associated with high water quality. Recent studies commissioned by MCD indicate that the number and diversity of bugs and fish living in a 5-mile stretch of the Great Miami River in downtown Dayton exceed expectations for this section of the river. We wanted to know if the river’s aquatic life would improve after the low dam near Monument Avenue in downtown Dayton was altered for paddling recreation. Before the kayak chutes were created, the low dam slowed the river’s flow under certain conditions. This lowered oxygen levels and made the river an undesirable place for species of bugs and fish that need lots of oxygen and clear water. Fish sample collected on the Great Miami River in Dayton With funding assistance from Five Rivers MetroParks, MCD hired the University of Dayton’s Jeff Kavanaugh, Ph.D., to conduct the studies. Kavanaugh and his student researchers collected data in 2014 and 2015 before the low dam was modified, and again in 2017 and 2018 after the low dam was altered. The studies took a close look at the diversity and population of the river’s fish and macroinvertebrate communities. Macroinvertebrates are stream bugs that live part of their lives underwater. Scientists track fish and bugs to determine a river or stream’s health because they can be sensitive to changes in habitat conditions and water pollution. If pollution-sensitive species are present in the river, experts believe the river is in good condition. Key findings from the study include:

• The fish community is diverse and abundant.
• The macroinvertebrate community is also diverse and abundant.
• The habitat conditions of the river channel are very good to excellent.

Dragonfly nymphs are an example of a macroinvertebrate found in the Great Miami River. Modifications to the low dam near Monument Avenue improved river channel habitat. The changes allowed healthier communities of macroinvertebrates to flourish, and the fish that feed upon those communities to return. The results from the study show this section of the river could meet the state’s highest criteria for water quality. The study also noted a few other factors that contribute to the health of this stretch of the Great Miami River:

• The City of Dayton does not have a combined sewer system. This eliminates periodic discharges of raw sewage into the river during rain events.
• Municipal wastewater treatment, thanks to requirements of the Clean Water Act, has played a major role in the recovery of the Great Miami River.
• The buried valley aquifer sustains flow in the Great Miami River during droughts. Abundant water flows even during the driest times of the year, typically summer and early fall, thanks to the aquifer.

Dr. Kavanaugh also studied the fish, bugs and habitat conditions in the area surrounding the Tait Station low dam before its removal. He will compare that data with data from studies completed after the dam was completely removed in 2018.

---