Documentation of lake sturgeon (Acipenser fulvescens Rafinesque, 1817) recovery and spawning success from a restored population in the Mississippi River, Missouri, USA

Lake sturgeon Acipenser fulvescens are considered rare and were nearly extirpated in the Mississippi River in Missouri by 1931 as a result of overfishing and habitat fragmentation. Propagation efforts have been implemented by the Missouri Department of Conservation since 1984 as means to restore the lake sturgeon population. Although recent population increases have been observed, a formalized evaluation to determine if lake sturgeon are self-sustaining in the Missouri portion of the Mississippi River has not been completed. Therefore, the objectives of this study were to: (i) determine the proportion of reproductive individuals, (ii) evaluate seasonal movement patterns of adults, and (iii) validate purported spawning locations within the Mississippi River in Missouri. Lake sturgeon catch data indicated that approximately 11 percent of the population are reproductively mature. Additionally, telemetry data confirms that the greatest movement by adult lake sturgeon occurs during spring, which suggests spawning behavior. Finally, it was possible to document lake sturgeon embryos and emergent fry larvae below Melvin Price Locks and Dam 26 in the Upper Mississippi River near St. Louis, Missouri. Water velocity, depth, and substrate size were measured at this location and embryos were collected and hatched in the laboratory. River gage data suggest that spawning behavior may have been elicited by a large influx of water during a drawdown period of water above the dam. This study represents the first documented spawning of A.fulvescens in the Mississippi River and highlights the success of recovery efforts in Missouri.