Lack of response of juvenile walleyes to increased levels of fertilizationor liming in soft-water ponds

The growth, survival, and production of juvenile walleyes Stizostedion vitr eum 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 a nd survival were both reduced in ponds stocked earliest in the season, rega rdless of the fertilization rate. This indicates that unpredictable spring weather is a more important factor than fertilizer nutrient levels in the p ond production of walleye. We tested the hypothesis that fish production wa s 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 re duce 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 alk alinities but again failed to affect fish growth, survival, or production. We concluded that the originally proposed fertilization rate provides suffi cient nutrient levels for the pond production of juvenile walleyes.