Otolith microchemistry reveals Northern Snakehead recruitment and dispersal patterns in Virginia tributaries of the Potomac River

Abstract Objective Understanding fish movement patterns can provide valuable biological and ecological insights for management, particularly when movement across interjurisdictional boundaries and ecologically significant habitats occur. Otolith microchemistry can elucidate broadscale movement patterns and help define population structure, identify relative stock contribution, and quantify dispersal patterns. We sought to quantify dispersal patterns of Northern Snakehead Channa argus across Potomac River tributaries. Our objectives were to determine movement between, or fidelity across, tributaries, identify potential recruitment sources, and delineate overall population structure. Methods To evaluate Northern Snakehead movement patterns, we assessed Sr:Ca and Ba:Ca ratios in juvenile and adult Northern Snakehead otoliths. Fish were collected across Virginia Potomac River tidal freshwater tributaries from Stafford County, Virginia (approximately 40 mi south of Washington, D.C.), to the Pentagon Basin, Washington, D.C. Linear discriminant function analysis was used to train and develop models. Models were evaluated and used to assign fish to known collection tributaries. Results Overall model accuracy was high (90%) at subbasin watershed (8-digit hydrologic unit) levels, and both elemental ratios appeared to increase downstream. These models were used to assign natal origin using otolith core signatures and revealed movement patterns, suggesting that dispersal rates may be high in certain environments. Natal fidelity was high downstream, and dispersal contributed to upstream populations. Conclusions Northern Snakehead dispersal appears to be high and likely facilitated expansion after ­introduction. Newly established populations may possess the capacity to rapidly colonize and disperse. Broad management and control strategies could target areas with high recruitment and dispersal capabilities.