Darby Creek Advocate Volume 10, Issue 1  March 2002

Preliminary Results in from 2001 Surveys

EPA Study Offers Good News, Bad News

Initial fish data from the EPA’s 2001 survey of the Darby watershed confirms that the creek is still home to a remarkably diverse fish community, especially for a medium-sized river system.

At the same time, the study suggests ongoing declines in several sensitive species, and reinforces concerns that parts of the watershed—particularly certain tributaries and headwater areas—are being impacted by a variety of stresses.

First the good news. Electroshocking and seining by biologists turned up 82 fish species, a number that is close to the expected fauna (depending on how you define a resident species, Darby has historically supported 86-96 fishes). And even though several rare species were not found in the current study, these were likely missing due to limited sampling in the lower Big Darby rather than to declines in their populations.

Four of the species found are considered rare or endangered in the state of Ohio, including the least darter, Tippecanoe darter, bluebreast darter, and river redhorse sucker.

Also encouraging was the fact that roughly two-thirds of the Big Darby mainstem scored high enough in fish diversity and fish health to satisfy standards for “Exceptional Warmwater Habitat” (EWH), the state’s highest classification. Several Big Darby tributaries also met this high standard, most notably the lower two-thirds of Little Darby Creek, the lower portions of Treacle Creek and Proctor Run, Pleasant Run, Spain Creek, and a second tributary named Little Darby Creek in the Big Darby headwaters.

Now the bad news. Results clearly show that the watershed has become increasingly fragmented, with numerous areas showing impacts that have led to a loss of fish species or a loss in fish health. Impacted areas either did not meet EWH standards, or have historic impacts that have led to their demotion to “Warm-water Habitat” (WWH), a listing that represents the typical degraded Ohio stream. A designation of WWH indicates that, in the EPA’s judgement, a particular stream or stretch of stream can no longer be expected to support a high level of fish diversity.

In the 2001 study, the most impacted parts of the watershed were some of Darby’s eastern tributaries. The poorest were Hamilton and Clover-Groff Ditch, two streams that meet to form Hellbranch Run in western Franklin County. Despite needing to meet only the lowered standards required of WWH streams, both still do not come close to expectations. Hamilton Ditch rated “poor to very poor,” while Clover-Groff rated “poor to fair.”

Hellbranch Run itself also shows heavy impacts. As recently as the 1980’s biologists considered Hellbranch one of the best small streams in the state. But today this important Darby tributary has been demoted to WWH. In the present study the upper half of Hellbranch failed to meet WWH standards. In its lower 4 miles, however, the stream improves a bit, and at two sites almost scored in the exceptional category. Still, even these moderately good scores represent a significant decline from scores achieved as recently as 1997. Declines are clearly the result of increased development upstream, and they come even as several wastewater treatment outflows have been cleaned up.

Other major eastern tributaries in poor condition include Sugar Run, Robinson Run, and Buck Creek. All three are classified as WWH, and for the most part all fail to meet the modest criteria for this category. Flat Branch, a major tributary in the Big Darby headwaters that flows through Honda property, has a special classification as “modified” WWH due to channelization. It also performs very poorly. Many smaller tributaries also show impacts.

Substandard results were not limited to tributaries. In Big Darby, impacts were seen below Plain City, around and below Milford Center (the site of an agribusiness spill in 2000), and in the headwater region (the river’s first 10 miles). In Little Darby, impacts were evident above state route 161 (the river’s first 10 miles or so).

In addition to poor fish scores at some locations, results confirm that certain sensitive species are declining at a disturbing rate. Many of these fall into the category of “prairie” fishes, a complex of species that once thrived in the Darby Plains area, but which, according to a soon-to-be-released study by Dr. Ted Cavender (OSU Museum of Biological Diversity), have declined in parts of the Darby watershed, especially in the upper Big Darby and its tributaries. Many of these species were found at only a few sites in the present survey.

In these preliminary results, the EPA has not identified the sources of impacts. These will be included in a report to be completed later this year. However, in the past the agency has attributed impacts to certain agricultural practices, wastewater outflows, leaking septic systems, hydrologic modifications, and runoff from developments. Identification of the sources of impacts will be an important component of the EPA’s study and will lead to recommendations on correcting problems.

Also yet to come are results of surveys for aquatic macroinvertebrates and water chemistry. The Advocate will update results in future issues.

DCA has also been meeting with EPA officials and other interested parties to insure that freshwater mussel data is included in the agency’s final report. These may reveal further problems not obvious from the fish data. Biologists consider mussels to be the most sensitive indicators of water quality, and there is great concern that declines in Darby over the last two decades point to a general decline in the ecosystem’s integrity that has not fully shown up in fish or other data.