Post-spawning distribution, abundance, and species-habitat associations of the Barrens darter (Etheostoma forbesi)

Identifying factors that influence habitat use is fundamental to developing conservation strategies for rare species. Knowledge of habitat relationships at multiple scales can also be useful for conservation efforts for rare stream fishes. The Barrens Plateau region of middle Tennessee harbors a number of unique and rare aquatic species, including the Barrens darter (Etheostoma forbesi). I studied the darter's distributional patterns at four spatial scales (microhabitat, reach, local, and network) to determine habitat variables significantly associated with Barrens darter presence or absence. During June -- October of 2009, I sampled 44, 100-m reaches in 29 streams for Barrens darters. GIS was used to examine the spatial distribution of the Barrens darter in relation to historic (1976) and current (2006) landcover at the local and network scales. At the reach scale, Barrens darter distribution was associated with five variables: link magnitude, stream gradient, dissolved oxygen, pH, and an index of bank erosion. Darters were more likely to be present in reaches with link magnitudes < 5, stream gradients between 0.3 and 0.8 % slope, and dissolved oxygen concentrations < 7.5 mg/l. With the exception of one site on Duke Creek (pH = 9), Barrens darters were more likely to be found in reaches with pH < 8 and low levels of bank erosion. Classification trees identified an important relationship between darter presence and dissolved oxygen, gradient, and total dissolved solids. Although six microhabitat variables were measured, my analyses did not reveal any important darter-habitat associations at this scale. Finally, at the local and network scales, I observed significant associations between landcover changes and Barrens darter distribution, suggesting that Barrens darters are more likely to occupy areas that have experienced less change in landcover from 1976 to 2006.