Scaphirhynchus Conference: Alabama, Pallid, and Shovelnose Sturgeon

St. Louis, Missouri, 11-13 January 2005

26.  HABITAT USE AND DIET OF HATCHERY-REARED JUVENILE PALLID STURGEON (SCAPHIRHYNCHUS ALBUS) AND JUVENILE SHOVELNOSE STURGEON (SCAPHIRHYNCHUS PLATORYNCHUS) IN THE MISSOURI RIVER ABOVE FORT PECK RESERVOIR, MONTANA

Paul C. Gerrity and Christopher S. Guy, Montana Cooperative Fishery Research Unit, 301 Lewis Hall, Department of Ecology, Montana State University, Bozeman, MT 59717; Phone 406-994-6643; FAX 406-994-7479; pcgerrity@montana.edu

William M. Gardner, Montana Department of Fish, Wildlife, and Parks, P.O. Box 938, 2358 Airport Road, Lewistown, MT 59457; Phone 406-538-4658; bgardner@state.mt.us

Natural recruitment of pallid sturgeon (Scaphirhynchus albus) has not been observed in the Missouri River above Fort Peck Reservoir, Montana, for at least 30 years.  In an effort to recover the species, 736 hatchery-reared juvenile pallid sturgeon (HRJPS) were released as yearlings in 1998.  Evaluation of these HRJPS is necessary to determine their performance in a natural lotic environment.  Therefore, we measured habitat variables at the locations of 29 HRJPS and 22 indigenous juvenile shovelnose sturgeon (JSNS) (Scaphirhynchus platorynchus) implanted with radio transmitters during the spring, summer, and autumn in 2003 and 2004.  In both years, HRJPS and JSNS used similar depths in June, while HRJPS used greater depths in July and August.  Average relative depth (defined as fish depth divided by maximum depth of the channel cross-section) of HRJPS increased from June through August, but changed little for JSNS.  Macrohabitat use (e.g., inside bend, outside bend, channel crossover) was highly variable for both species.  We also examined the diets of all HRJPS and JSNS captured in 2003 and 2004 using a gastric lavage.  Fish composed the majority of the diet of HRJPS, while JSNS primarily consumed aquatic invertebrates.  These data suggest that pallid sturgeon are piscivorous as juveniles.  The observed differences in depth used by pallid sturgeon and shovelnose sturgeon may be related to the dissimilarity in food habits.