Factors Affecting Walleye Recruitment in Lake Oahe, South Dakota, 1982-2010

Factors influencing Walleye recruitment vary by system and region.  Fluctuating water levels, climatic variation, and stock characteristics are thought to influence Walleye recruitment in reservoirs. Accordingly, we developed a set of candidate models to examine the relationship between Walleye recruitment and climate, water level, and spawning stock characteristics during 1982-2010 in Lake Oahe, a large impoundment of the Missouri River located in South Dakota and North Dakota.  We used age-2 relative abundance from standardized gill netting surveys as an index of Walleye recruitment, and used a Ricker stock-recruitment model modified by covariates to explain recruitment variation.  The most supported models suggested that abiotic factors including large water level increases and warm spring temperature positively influenced Walleye recruitment.  Specifically, large increases in reservoir elevation following drought in the mid-1990s and the late 2000s were associated with strong year-classes.  Spawning stock size and condition varied substantially across years, but models including spawning stock size and condition received little support, suggesting that stock characteristics were less important than abiotic factors in regulating Walleye recruitment.  Our results provide managers a tool for predicting year-class strength and suggest that water level management may be used to create favorable conditions for Walleye recruitment.