Quantifying Seasonal Movement of Smallmouth Bass in the Susquehanna River

Smallmouth bass (Micropterus dolomieu) are both a socieconomically prized sportfish as well an apex predator. In the Susquehanna River basin, smallmouth bass populations declined in the 1990s through the early 2000’s and although populations appear to be relatively stable in recent years, there are still concerns over what caused the initial decline. In addition, there remains uncertainty as to what has caused more recent incidences of disease and young-of-year mortality events. Several factors that may be affecting smallmouth bass health have been identified, including pathogens (e.g., bacteria, viruses, and parasites), contaminants (e.g., endocrine disruptors), and water quality conditions (e.g., elevated stream temperatures). Because the duration and frequency of exposure to these potential stressors is largely dictated by how smallmouth bass move and utilize different habitats, understanding the movement ecology of this species is critical. To address this issue, we used radio-telemetry to study movement and river and tributary habitat use of smallmouth bass in the Susquehanna River basin. Understanding movement patterns will provide insight on where fish could be spending large amounts of time, and therefore help understand where and when they might be exposed to various stressors. This study demonstrated key movement periods related to spawning and overwintering. Several fish utilized tributaries for spawning, but spent the majority of the time in the main-stem of the West Branch of the Susquehanna River. Overall movement varied substantially among individual fish, ranging from under a kilometer to over 90 km during the study duration (from May 2014 to June 2015). The results of this telemetry study have implications for studying disease and contaminant-related stressors in smallmouth bass and for fisheries management, including harvest regulations.