Distinguishing and employing sister species of fish in assessment of stream quality

Biological indicators (bioindicators) can be individual species or species groups used to assess habitat quality. Unfortunately, conservationists often lack information on species distribution, how to differentiate between similar species, and environmental conditions associated with the presence of a species. We addressed these problems using two “sister” species of fish, the Mottled Sculpin (Cottus bairdii) and the Slimy Sculpin (Cottus cognatus), as stream quality indicators in the Manistee River watershed in the Huron-Manistee National Forests in Michigan, USA. We determined the abundance and distribution of these species and related their presence to concurrent in-stream measurements of temperature, dissolved oxygen, pH, conductivity, turbidity, and stream quality score based on macroinvertebrate diversity. To be certain of identification, we sequenced the Cytochrome c Oxidase Subunit I (CO1) molecular marker for specimens and used it as a DNA barcode to determine a specimen’s species. Cladistic analyses of CO1 unambiguously supported recognition of Mottled Sculpin and Slimy Sculpin as distinct species, confirming initial 87.5% correct identification using morphological characteristics, with uncertainty limited to juvenile fish. Field determinations increased to 100% correct identification as investigators gained more experience. Both species were most abundant in headwater regions, decreased downstream, and were sympatric at several locations. Mottled Sculpin were more likely to be found at stream locations with lower conductivity, pH, and stream quality scores, whereas Slimy Sculpin presence was more strongly associated higher levels of DO and lower levels of turbidity. Such findings are important because Mottled Sculpin are a designated management indicator species of the US Forest Service in the Huron-Manistee National Forests, but may be ineffective as a habitat quality indicator when used alone. Concurrent use of Mottled Sculpin and Slimy Sculpin as a management indicator sister-species complex could allow sufficient landscape coverage to permit habitat assessment if species-specific differences in environmental tolerances are precisely determined.

Effects of Stormwater Management and an Extended Culvert on Stream Health in Dug Run, Allen County, Ohio, USA

Changes in stream hydrology and habitat—associated with urbanization—have impacted diversity, abundance, and movement of both macroinvertebrates and fish. In 2008 the University of Northwestern Ohio began developing the western half of the campus, incorporating stormwater management practices. This provided an opportunity to examine 3 sections of the Dug Run stream that flows through campus: 1 section on the western half of campus that filters stormwater through the soil, and 2 sections on the eastern half of campus which are affected by both urbanization and a culvert that extends under a building and a road. Significant differences in macroinvertebrate Stream Quality Monitoring (SQM) index scores ( p < 0.001), fish diversity ( p < 0.010), and abundance of Orangethroat Darters (Etheostoma spectabile) ( p < 0.001) were observed between the western and the 2 eastern sections of Dug Run. Lower SQM index scores and lower Orangethroat Darter abundances were found in the urbanized sections of the stream, while lower fish diversity numbers were found upstream of the culvert. The western portion of campus, designed to filter stormwater runoff through the soil, was the only section studied with sensitive macroinvertebrates, a higher SQM index score, and a greater abundance of Orangethroat Darters.