Physiological and behavioral impacts of railway noise on stream fishes

Abstract

While the expansion of anthropogenic noise studies in aquatic habitats has produced conservation-based results for marine organisms, little attention has been paid to the potential impacts of anthropogenic noise on freshwater stream fishes. Recent work showed that Blacktail Shiner (Cyprinella venusta) exhibited multiple responses to road noise, however, community-wide effects of anthropogenic noise pollution have not yet been investigated. By examining six metrics of stress on four ecologically and evolutionarily disparate species of stream fishes (Campostoma oligolepis Largescale stoneroller; Etheostoma rufilineatum, Redline Darter; Cyprinella venusta; and Lepomis macrochirus, Bluegill Sunfish), these laboratory experiments aimed to describe the potential impacts of anthropogenic noise on these understudied organisms. Each species included represents a unique combination of hearing sensitivity and water column position. The anthropogenic noise source used throughout this research consisted of an underwater audio recording of a train crossing a stream via a beam-style bridge. Physiological and behavioral metrics were compared across the presence and absence of noise playback. In addition, measurements of water-borne cortisol were collected from Blacktail Shiner exposed to rail-noise presented in variable temporal arrangements to further elucidate dynamics of the primary stress response in this species. Noise playback had no statistically significant effect on blood glucose or water-borne cortisol levels, however, repeatedly decreased concentrations of water-borne cortisol observed in Blacktail Shiner implies potential inhibition of a neuroendocrine stress response. The presence of noise produced significant changes in ventilation rate, total distance swam, average swimming velocity, and the elicitation of a startle response in a portion of the species observed. Effects of noise were observed in certain species contrary to what would be hypothesized based on their theoretical hearing sensitivity. These results demonstrate that predicting susceptibility to this type of stressor cannot be accomplished by simply considering hearing ability or water column position. More importantly, we show that anthropogenic noise can disrupt a variety of behavioral and physiological processes that potentially serve as proxies for fitness-impacts and should be considered an environmental stressor and a driver of habitat degradation to the affected species and potentially communities.