Craig Paukert and William Fisher, Oklahoma Cooperative Fish and Wildlife Research Unit, Oklahoma State University, 404 Life Sciences West, Stillwater, OK 74078

Abstract. Our objective was to determine the effects of water chemistry and hydrology on the diurnal and nocturnal movement rates and distributions of paddlefish Polyodon spathula in Keystone Reservoir. Ultrasonic telemetry was used to monitor six paddlefish throughout the summer. Paddlefish were located during three, three day-long daytime and three, three night-long nighttime trips. At each location, a global positioning coordinate and 1-m profiles of water chemistry were taken. Paddlefish moved more at night (mean=784 m/h) than during the day (mean=348 m/h). Nighttime movement rates were negatively correlated with reservoir height, inflow, and discharge; there were no significant correlations for daytime movements. Fish location was also correlated with reservoir height, inflow and discharge, although daytime location was more strongly correlated than nighttime location. Paddlefish were located in the less conductive Arkansas Arm and below the Cimarron River/Arkansas River confluence. Although the Arkansas and Cimarron arms of the reservoir were similar in temperature and dissolved oxygen, conductivities were double in the Cimarron arm, which may deter paddlefish from entering this tributary in summer. However, paddlefish move up the Cimmaron River to spawn in spring.