Distribution and movement of juvenile paddlefish in a mainstem Missouri River reservoir

Hatchery-raised paddlefish (Polyodon spathula) were implanted with ultrasonic transmitters and tracked from August to November 1998 and March to November of 1999 and 2000 to determine diel movements and seasonal distribution in Lake Francis Case, South Dakota. Juvenile (340 to 432 mm eye to fork length) paddlefish (N=32) exhibited variable movement patterns but remained in the upper reservoir reaches throughout the three-year study. Movement rates ranged from 35 to 3,464 m/h with 90% of all locations in the upper third (51 km) of the reservoir. Increased movement rates were weakly correlated with increased water temperature (r=O. 16, P=0.04). Daytime paddlefish movement peaked in July and August. However, diel movements were variable among seasons. In spring, movement rates did not differ among diel periods, whereas summer movements were lower during crepuscular periods and fall movements were lowest during the day. Although paddlefish were stocked at two locations in Lake Francis Case, they appeared to disperse and use reservoir areas similarly.