Using Ultrasonic Telemetry to Evaluate Paddlefish Spawning Behavior in Harry S. Truman Reservoir, Missouri

Large‐river fishes (e.g., sturgeons [Acipenseridae] and Paddlefish Polyodon spathula ) that inhabit reservoir systems are potentially unable to sense environmental cues that elicit typical life history behaviors. These cues can be masked by altered hydrology and temperature regimes. In many reservoirs throughout North America, Paddlefish populations are potentially affected by these unnatural conditions. In an attempt to understand and identify the potential mechanisms that limit Paddlefish reproduction in reservoir systems, we selected Harry S. Truman Reservoir (Truman Lake), Missouri, as our study area of focus. This population is supplemented by stocking, and although anecdotal evidence of potential natural reproduction exists, spawning has never been documented. We implanted ultrasonic transmitters into 113 reproductively mature Paddlefish, and the movements of these fish were tracked over 2 years. Paddlefish migratory behavior was significantly related to water temperature and gauge height, and differences in movement behaviors existed between sexes. Spring aggregations were located in the riverine portion of the Osage River, and embryos and larvae were sampled in 2015 and 2016 near said aggregations. Using acoustic telemetry and egg mats, we acquired evidence suggesting that the Truman Lake Paddlefish are spawning. Our technique can likely be applied to determine spawning locations for Paddlefish inhabiting other large reservoirs.