No abstract

Sauger Sander canadensis provide a popular, harvest‐oriented fishery throughout the Ohio River and are managed jointly by the state fisheries resource agencies through the Ohio River Fisheries Management Team. For more than two decades, the Ohio River Sauger population has been dominated by small (<356 mm), young (<3 years old) individuals. Recently, Sauger abundance in the Ohio River has been near or below long‐term averages. Together, these observations prompted concern that overfishing may be occurring and that more restrictive harvest regulations may be necessary. We summarized Sauger population characteristics (abundance of age‐0 Saugers, abundance of Saugers ≥280 mm TL, growth, and mortality) based on data from Ohio River Fisheries Management Team population assessments conducted during the period of 2005–2017 and modeled the potential outcomes of applying a 356‐mm minimum length limit. During the period 2005–2017, abundance of age‐0 Saugers and abundance of Saugers ≥280 mm TL was greater with distance downstream but generally declined through time. Growth rates and total annual mortality rates increased with distance downstream and had no apparent temporal trends. Yield‐per‐recruit models showed that where Saugers grow fastest (i.e., downstream pools), implementing a minimum length limit could improve size structure and increase yield. However, where Saugers grow slowly (upstream pools), size structure would only increase marginally, and yields would likely decrease with a minimum length limit. Upstream to downstream gradients in Sauger population characteristics may therefore lead to differences in the effectiveness of length‐based regulations among Ohio River pools. Fisheries managers must therefore consider trade‐offs between the size of fish at harvest and yield before implementing minimum length limits.

Objective: Create a quicker and more accurate genetic assignment tool for Walleye Sander vitreus broodstock in the Eastern Highlands region and to quantify genetic diversity of four Walleye populations using next-generation sequencing. Methods:To determine the impacts of stocking nonnative Great Lakes strain Walleye on local populations, three Appalachian populations were sampled: two native populations (Rockcastle River, Kentucky, and New River, Virginia) and one population founded from the Great Lakes strain (Tygart Lake, West Virginia). Walleye from Lake Erie were used as a reference for the Great Lakes strain. Utilization of a genotype-by-sequencing approach supported genome-wide estimates of genetic diversity, population structure, and creation of two single-nucleotide polymorphism assays that can be used to rapidly identify Great Lakes-strain, native Eastern Highland-strain, and F 1 hybrid Walleye. Result:Results indicate that the four populations we evaluated were genetically distinct from one another and that each population contains varying degrees of genetic differentiation relative to its source population. The stocked Tygart Lake population displayed lower genetic diversity in metrics such as nucleotide diversity (0.172 vs. 0.184), private alleles (4057 vs. 7623), and observed heterozygosity (0.163 vs. 0.204), likely indicative of genetic drift stemming from a founder effect. The two native populations displayed varying levels of genetic diversity. The New River population was found to have a higher ancestry of the Great Lakes strain in their genome than the Rockcastle River population, reflecting the known admixture of New River Walleye following historic stocking of Great Lakes-derived Walleye. Our results also identified a pure native Eastern Highlands strain population that can be used for future augmentation and restoration of Eastern Highlands Walleye. Conclusion:Our results provide a diagnostic single-nucleotide polymorphism assay to quickly identify Great Lake strain, Eastern Highland strain, and their F 1 hybrid for future management efforts and provide key population genetic insights to managers to enhance best management practices.