Factors influencing recruitment of shovelnose sturgeon in the upper Missouri River basin

Understanding recruitment and identifying factors influencing annual variations in recruitment are primary goals of fisheries biologists and resource managers.  A spatially and temporally intensive study was conducted during 2003-2009 in the upper Missouri River and lower Yellowstone River of Montana and North Dakota to examine annual recruitment variations in shovelnose sturgeon Scaphirhynchus platorynchus and identify factors influencing recruitment.  Based on benthic trawl samples of young-of-year shovelnose sturgeon collected at weekly intervals from mid-summer to early fall, apparent strong year classes of shovelnose sturgeon were produced in three years (2003, 2005, 2007) and weak year classes were produced in four years (2004, 2006, 2008, 2009).  Correlative analyses between environmental data and catch rates of young-of-year shovelnose sturgeon suggest that water temperature and discharge during the spawning, incubation, and larval life stages influence year class strength of shovelnose sturgeon in the upper Missouri River basin.  Whereas earlier studies have identified that shovelnose sturgeon in the upper Missouri River basin exhibit annual variability in recruitment, results from this study extend the knowledge base to suggest that environmental conditions during the early life stages are important factors influencing recruitment.