COS 42-8
Patterns in fish assemblage structure in the eastern Fayetteville Shale, Arkansas
Hydraulic fracturing has recently become prevalent in the Fayetteville Shale of north-central Arkansas. Accompanying the actual fracking process are intensive road and wellpad construction activities, as well as water withdrawals and potential release of product fluids into streams. The effects of these potential disturbances on stream fishes are poorly understood. Within the Fayetteville Shale region, fish assemblages have been generally well sampled from larger streams, but our knowledge of very small (< 10m wide) streams in the region is still lacking. Entrekin et al. (2011) demonstrated that such streams are more likely to be in proximity to natural gas extraction activity. Before robust predictions of the effects of natural gas extraction activity can be made, the systems which they may be affecting must be understood to some degree. We therefore began sampling fishes from multiple streams < 10m wide representing a range of environmental conditions in the eastern Fayetteville Shale to address the questions of what fish assemblages would characterize these streams, and which environmental variables would relate to assemblage structure. Fishes were collected from multiple sub-plots using quantitative multiple pass depletion techniques, while environmental variables were collected both in-stream at sites and with geospatial analysis techniques.
Results/Conclusions
When comparing IBI metrics to environmental variables with partial correlation analysis, most related significantly to stream size (e.g, species richness, r = 0.65, and percent of simple lithophilic spawners, r = -0.48), while percent darters (r = 0.64) related significantly to forested land use and the percent of green sunfish + bluegills + yellow bullhead related significantly to the density of natural gas wells (r = 0.75). Ordination analysis recovered a primary species gradient (64% of information in original distance matrix) which graded from simple assemblages of redfin shiner, orangethroat darter, and redfin darter, to complex assemblages with many large-stream and potamodramous forms. This species gradient related significantly to an environmental gradient complex consisting of stream size (r = 0.74), elevation (r = -0.65), aquatic vegetation (r = 0.52), and forested land use (r = -0.50), reflecting a pattern of forested hills and pastoral wider floodplains present in central Arkansas. We also recovered two minor species gradients relating to forested land use (r = -0.47) and local stream slope (r = 0.51), respectively. From these analyses we discuss variables which future researchers should bear in mind when designing experiments to sample fishes in headwater streams in the eastern Fayetteville Shale.