Radiogenic strontium isotope ratios ( Sr: Sr) in otoliths were compared with isotope ratios predicted from models and observed in water sampling to reconstruct the movement histories of smallmouth bass Micropterus dolomieu between main-river and adjacent tributary habitats. A mechanistic model incorporating isotope geochemistry, weathering processes and basin accumulation reasonably predicted observed river Sr: Sr across the study area and provided the foundations for experimental design and inferring fish provenance. Exchange between rivers occurred frequently, with nearly half (48%) of the 209 individuals displaying changes in otolith Sr: Sr reflecting movement between isotopically distinct rivers. The majority of between-river movements occurred in the first year and often within the first few months of life. Although more individuals were observed moving from the main river into tributaries, this pattern did not necessarily reflect asymmetry in exchange. Several individuals made multiple movements between rivers over their lifetimes; no patterns were found, however, that suggest seasonal or migratory movement. The main-river sport fishery is strongly supported by recruitment from tributary spawning, as 26% of stock size individuals in the main river were spawned in tributaries. The prevailing pattern of early juvenile dispersal documented in this study has not been observed previously for this species and suggests that the process of establishing seasonal home-range areas occurs up to 2 years earlier than originally hypothesized. Extensive exchange between rivers would have substantial implications for management of M. dolomieu populations in river-tributary networks.

Reconstructing individual growth history from analysis of increments in otoliths, scales, or spines can provide information on past growth responses to environmental variation, which in turn can be useful for predicting population-level response to climate change. The objective of this study was to examine correlations between body length and different metrics of otolith size for Micropterus dolomieu. Three metrics corresponding to commonly-used microstructural and ultrastructural otolith dimensions were measured using image analysis of digital micrographs from a sample of 214 M. dolomieu ranging from 115 to 438 mm total length collected in 2011-2013. It was found that anteroposterior length of whole otoliths provided much improved regression relationships with body size as well as ease of data collection and faster sampling throughput compared with microstructural measures from polished sections. When applying these metrics to reconstruct growth history the biological intercept model generally produced more reasonable back-calculated estimates of length-at-age, although this was not consistent across all otolith metrics. Results suggest that whole otolith measures should be employed due to efficiency of data collection and greater reliability for reconstructing growth history in M. dolomieu.

The trophy fisheries for Muskellunge Esox masquinongy in the northern U.S.A. and Canada often are developed and maintained by using high minimum‐length limits (MLLs). However, the effectiveness of using such MLLs on southern‐latitude Muskellunge populations, which have different rates of growth and mortality, warrants further research. The Muskellunge fishery in the New River, Virginia, was managed under a 30‐in (75 cm) MLL until 2006 when the MLL was increased to 42 in (105 cm) to increase the abundance of large Muskellunge. We measured fishery quality before and after the institution of the 42‐in MLL using size structure, average individual condition, rates of growth and mortality, and CPUE. We also assessed the potential of alternative length regulations (other MLLs and a 40–48‐in protected‐slot limit) to improve the population's size structure and trophy production using simulation models in the Fisheries Analyses and Modeling Simulator (FAMS) program. Following the institution of the 42‐in MLL, we observed a 5‐in increase in the average size of Muskellunge, an increase in the population's size structure with greater proportions of memorable‐size individuals (≥42 in) and an increase in the abundance of memorable‐size Muskellunge. However, declines in the average condition, i.e., relative weight (Wr), of large Muskellunge (≥38 in) suggest there is possible stockpiling of individuals just below the 42‐in length limit. Higher MLLs (e.g., 48‐in MLL) could further improve fishery quality by increasing the survival of Muskellunge to large trophy sizes (≥50 in). However, managers should be wary of stockpiling under alternative MLLs as well. Furthermore, a higher MLL is unlikely to garner broad angler support in this system. Conversely, a protected‐slot limit that allows the production of some trophy‐sized Muskellunge while reducing the overall number of individuals, and that limits potential for stockpiling, may be a more agreeable regulatory option for New River fishery managers. These findings and the methods described within this study may be useful for fisheries managers working on other Muskellunge fisheries in southern systems.