The Fishes of the Fayetteville Shale: Environmental Factors Relating to Assemblage Structure

Novel anthropogenic disturbances such as nontraditional natural gas extraction pose conservation challenges for ecologists. One major challenge in studying the impacts of such activities is that they occur in gas plays with spatial boundaries defined more by historical geology than by environmental factors. Thus, much variation in assemblage structure within a gas play from environmental factors might be expected. We examined the relationships between major habitat variables within the Fayetteville Shale of north-central Arkansas and stream fish assemblage to provide a baseline set of expectations for future surveys in the region. Fishes were sampled using a quantitative multiple pass depletion methodology on 21 streams representing a variety of headwater habitats in the region. We ordinated sites in species-space using Nonmetric Multidimensional Scaling to examine underlying trends in assemblage variation. NMS resolved a three axis solution relating to catchment size, gradient, and drainage basin. A remarkably rapid increase in species richness and changes in assemblage composition occurred across a relatively small range of catchment sizes. Drainage basin appeared to constitute the least amount of variation in headwater assemblage structure. Our results suggest that future researchers should pay particularly close attention to environmental gradients when conducting assemblage surveys within the Fayetteville Shale.