Date of Award

January 2022

Degree Type

Open Access Thesis

Document Type

Master Thesis

Degree Name

Master of Science (MS)

Department

Biological Sciences

First Advisor

Sherry L. Harrel

Department Affiliation

Biological Sciences

Second Advisor

David R. Brown

Department Affiliation

Biological Sciences

Third Advisor

Amy Braccia

Department Affiliation

Biological Sciences

Abstract

The Buck Darter (Etheostoma nebra) is an imperiled, small-stream species in the Cumberland River drainage in southern Kentucky. It was originally thought to be a population of the Striped Darter (E. virgatum) species and was prevalent throughout the Buck Creek system. It was separated from the Striped Darter and deemed a separate species in 2015; however, the population has declined dramatically. Presently, the species is found in three streams of the Flat Lick Creek system, two originally established populations in Big Spring Branch and Stewart Branch, and one newly introduced population, established in 2018, in an unnamed tributary. The decline in population makes it important to understand the Buck Darter spawning habits and nesting habitat. Thus, my study objectives were to compare populations of established and introduced Buck Darters and determine differences in spawning habitats, conductivity, and effects of temperature on timing of spawning and nest densities; as well as compare spawning habitats, conductivity, and effects of temperature on timing of spawning and nest densities between the Striped Darter (in Beaver Creek, Cumberland River drainage) and Buck Darter populations. Two 120-m reaches were observed for each stream throughout the spawning season. Slab rocks were checked for active nests and habitat measurements were taken at each nesting site. Buck Darters nested in shallow, slow-moving water located closer to the streambank than the center of the stream. Nests of established populations were found at greater stream widths with nests located farther from the streambank than nests of the introduced population, most likely a factor of stream size overall. Nesting sites also differed in flow velocity, with the unnamed tributary having nests in slower moving water. At Beaver Creek, conductivity and dissolved oxygen were lower, and Striped Darters nested in areas with greater stream width, and nests were located farther from the nearest streambank than the established Buck Darter populations. Weekly nest densities were similar between the established and introduced populations and were lower in the Striped Darter population, possibly a factor of nest rock availability. The established and introduced Buck Darter populations also had a longer average nesting season (15.7 weeks) than the Striped Darter (6 weeks). Water temperature showed a significant effect on nest density in the unnamed tributary (p = 0.020) but not in any of the other streams. It did have an impact on timing of nesting, with all three groups starting the nesting season around 9-13°C and ending around 19-22°C. The Striped Darter population began nesting at a later start date and ended at an earlier date due to the colder start to the season and sharper increase of temperature throughout the season compared to the introduced and established Buck Darter streams. Comparing the Buck Darter’s nest habitat and densities to the introduced population and the Striped Darter allows us to observe how they are surviving in the unnamed tributary and what differences there are between their declining population and the persisting Striped Darter species. This knowledge will aid in finding and restoring new streams in the Buck Creek watershed for the Buck Darter and hopefully help to slow the decline of their population.

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