ABSTRACT
A B ST R A C T . Tremendous variation in survival and growth o f per cid fry stocked in ponds was addressed through manipulation o f amounts and kinds o f fertilizers added and stocking densities o f fish. Ponds were filled with water from nearby eutrophic lakes less than one w eek prior to stocking. Survival in these ponds averaged 64%, whereas ponds filled one month before stocking averaged only 14%. Optimal inorganic fertilization was identified as w eeldy restoration to 600 fig N /L (NH4 + N O 3) and 30 fig P/L as PO4. Organic fertiliza tion gave variable results and water qualities. In one experim ent, low organic fertilization alone (28 kg alfalfa m eal/ha/week) pro vided survival and growth comparable to optim al fertilization with inorganic nutrients. A lthough similar in results, inorganic fertiliza tion was more cost effective than the alfalfa meal. Low fish predation from low stocking or survival allowed Daphnia to overgraze algae. This resulted in a crash in both algae and zooplankton in the ponds. D oubling the initial stocking density increased harvests from 150,000 to 300,000 fish/ha and increased yield from 45 to 100 kg/ha.
