Inference on Movement and Growth of Smallmouth Bass in River-Tributary Networks from Otolith Chemistry and Microstructural Analysis

Understanding the movement of fish among networks of connected rivers is important for managing populations and fisheries from a basin-wide perspective.  As resources for survival, growth, and reproduction differ between these adjacent habitats the variable influence these have on population dynamics in space and time shapes the productivity, stability, and resilience of these populations across the riverscape.  We studied movement and growth of smallmouth bass (Micropterus dolomieu) in the middle James River and its major tributaries in the Piedmont region of Virginia, which constitutes one of the state’s flagship trophy sport fisheries.  Isotopic and elemental chemistry of otoliths was used to reconstruct movement history of individuals and investigate the frequency of dispersal between rivers, and otolith microstructure was used to back-calculate growth rates.  We found evidence for substantial movement between rivers occurring throughout life history stages represented in our sample.  Preliminary analysis did not reveal a correlation between movement history and annual growth; however, these data are being augmented with wider collections and analyses in summer 2012.  As average growth rates vary between the mainstem and its smaller tributaries, movement among these habitats may influence overall growth rates in the population and therefore could be considered in management strategies for trophy fisheries.