Spatial Gradients in Population Characteristics of Ohio River Sauger and Implications for a Length‐Based Regulation

Abstract

AbstractSauger 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.