Effects of Organic Enrichment on Zooplankton Abundance and Walleye Fry Growth and Survival in Artificial Rearing Ponds

Abstract

ABSTRACT Cylindrical aluminum enclosures in an artificial rearing pond were used to examine the effect of organic enrichment with alfalfa pellets and fish predation on the abundance and size structure of cladocerans and the growth and survivorship of walleye (Stizostedion vitreum vitreum) fry. Organic enrichment had a stronger effect than walleye fry predation on cladoceran abundance. Increased cladoceran abundance was due to increased abundance of smaller individuals, suggesting organic enrichment stimulated cladoceran reproduction. Although fish predation did not influence total cladoceran abundance, it did appear to reduce the abundance of larger size classes of cladocerans (> 1.25 mm total length). Organic enrichment did not increase survival of walleye fry but did increase their average weight and condition, especially among larger fry.