Lack of Response of Juvenile Walleyes to Increased Levels of Fertilization or Liming in Soft-Water Ponds

The growth, survival, and production of juvenile walleyes Stizostedion vitreum were not affected by increasing the rates of inorganic fertilization in earthen ponds by two and four times the originally proposed levels of 600 mu g nitrogen/L and 30 mu g phosphorus/L at each application. Fish growth and survival were both reduced in ponds stocked earliest in the season, regardless of the fertilization rate. This indicates that unpredictable spring weather is a more important factor than fertilizer nutrient levels in the pond production of walleye. We tested the hypothesis that fish production was carbon limited in these low alkalinity ponds by adding lime to some ponds as an experimental treatment. Ponds were stocked later in the spring to reduce variability due to weather. Total alkalinities increased in the limed ponds, but there was no effect on walleye growth, survival, or production. Additional large doses of limestone to all ponds further increased pond alkalinities but again failed to affect fish growth, survival, or production. We concluded that the originally proposed fertilization rate provides sufficient nutrient levels for the pond production of juvenile walleyes.