Environmental Influences on Early Development and Year-Class Strength of Northern Pike in Lakes Oahe and Sharpe, South Dakota

Abstract

Abstract Survival of artificially-fertilized ova and larvae of northern pike, Esox lucius, was estimated from embryos held in natural spawning areas in Lake Oahe and Lake Sharpe, two main stem Missouri River reservoirs. Mortalities approaching 100% during early embryonic development were associated with sudden drops in water temperature below 10 C or prolonged temperatures near 5 C. Silt deposition of 1.0 mm per day was associated with mortality of 97% or above. Following hatching available food appeared to be a more important factor in survival than temperature change or silt deposition. Estimates of year-class strength of northern pike in the two reservoirs suggest that large year classes were associated with stable to rising water level and temperature, flooded vegetation, and calm weather during the spawning season. Small year classes have been associated with abrupt water temperature fluctuations, dropping water level, and high silt deposits.