Telemetry was used to evaluate seasonal and diel movement patterns, general habitat use, survival, and spatial distributions of hatchery‐reared juvenile pallid sturgeon Scaphirhynchus albus stocked in the Missouri River below Fort Randall Dam, South Dakota and Nebraska. Sampling occurred at about 2‐week intervals during spring through fall. Of 22 ultrasonically tagged fish, 13 were intensively followed to assess hourly diel movement rates. A total of 258 relocations were made for the 22 tagged fish; 19 fish were relocated at least once, and 16 were relocated multiple times. At least 68% of tagged fish survived for 2.5 years. In 2000, fish were found mainly upstream of the stocking site, whereas in 2001 and 2002 the entire reach was used. Juveniles were found primarily in the main channel at depths exceeding 80% of the maximum channel cross‐section depth, where bottom current velocities ranged from 0.1 to 0.9 m/s. Clusters of juvenile pallid sturgeon (i.e., two or more fish) within 750 m of each other were observed on 15 dates, and clusters of juveniles within 500 m of each other were observed on 10 dates. Clusters were observed during all seasons. Mean (±2 SE) range of movement was significantly less in 2000 (8.3 ± 5.8 km) than in 2001 (29.3 ± 8.8 km) and 2002 (28.9 ± 15.0 km). We detected no significant differences in movement rates among years, seasons, or diel periods (i.e., dawn, daytime, dusk, and night). Our study indicates that range of movements of juvenile pallid sturgeon based on shorter studies (i.e., ≤1 year) should be interpreted cautiously because hatchery‐reared fish may not have acclimated to the riverine environment until the second year after stocking. Based on survival and distribution of juvenile pallid sturgeon throughout the study area, we conclude that this reach is suitable for recovery efforts.
We used ultrasonic telemetry to determine the distribution, seasonal migration patterns, and site fidelity of adult paddlefish Polyodon spathula in a main‐stem Missouri River impoundment. Thirty‐two adult paddlefish collected from two different spring congregation areas in Lake Francis Case, South Dakota, were surgically implanted with ultrasonic tags and relocated monthly from March to November 1994–1996. Paddlefish tagged in the Big Bend tailwaters were captured in this area and in another possible spring congregation (the White River) during prespawning and spawning periods, whereas paddlefish tagged in the White River were never located in the Big Bend tailwaters or in areas above the White River. Male and female paddlefish used reservoir habitats similarly except during the prespawning period, when male paddlefish used the White River more than would be expected by chance and all females implanted at the White River site remained below the White River. In both the postspawning and winter periods, all paddlefish moved downstream and congregated in the lower reservoir reaches. Up to 62% of males and 36% of females returned to their original capture site during the presumed spawning period at least 1 of the 2 years after tagging. Thirty‐one percent of males at large for 2 years returned to their initial spring capture location each of the following years, but only 9% of females returned. Our results indicate that some paddlefish exhibited site fidelity to the areas where they were captured (i.e., the White River) and presumably attempted to spawn, although winter distribution was similar among all tagged paddlefish. Restoration and stocking efforts may need to focus on habitat management at the locations where paddlefish may spawn, given adequate substrate.
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