Date of Graduation

Summer 2023


Master of Science in Biology



Committee Chair

Quinton Phelps


Dynamic rate functions (i.e., recruitment, growth, mortality) structure fish populations and are subject to latitudinal differences. These latitudinal differences are likely reflective of climatic variation and may result in spatially distinct populations that must be managed independently, especially in large systems such as the Upper Mississippi River system (UMRS). In order to successfully manage this system, an understanding of what drives these populations is required. The UMRS is useful for this investigation as it crosses 10° temperate latitude with widespread fish species found throughout. In this study, I investigated the synergistic relationship between latitude, vital rates, and abundance. Species were selected 1) to represent a wide range of species traits and reproductive strategies and 2) that could be collected solely through routine monitoring (LTRM) without additional targeted collections. Spatial distinctions in dynamic rate functions were found among study reaches. These insights play a vital role in determining management strategies for the UMRS. This study demonstrates the relationship between latitude, vital rates, and abundance within a riverine fish community, allowing for the informing of management decisions in a complex system. Northern Snakehead (NSH) are a species native to eastern Asia but have since been introduced around the world, both unintentionally and intentionally. These fish were first documented in the Potomac River system in 2004 and have since spread and established throughout the Chesapeake Bay watershed. Past studies have documented growth, movement, and diet, and found that the Potomac River population was characterized by variable recruitment. To that end, I sought to quantify what drives this variability. I employed an information-theoretic approach (AICc) to select a model to explain the recruitment patterns of Potomac River NSH. In the summer of 2021, juvenile NSH were captured in four tributaries. The selected recruitment variability model contained mean discharge and mean chlorophyll-a concentration in June and the coefficient of variation in May discharge. Young-of-year (YOY) NSH growth rates were high (about 2mm/day), and stomach contents displayed various diet items. Our recruitment variability results represent the first explanation of recruitment drivers for Northern Snakehead in the Potomac River. Further, NSH YOY results reflect the early shift to piscivory displayed by juveniles. These results are unique and can be used to inform management for a species that continues to establish itself in the Chesapeake Bay watershed.


population dynamics, management, Mississippi River, Potomac River, Northern Snakehead

Subject Categories

Aquaculture and Fisheries | Population Biology


© Aaron P. Muehler

Available for download on Friday, August 01, 2025

Open Access