IV. Abstracts of Technical Reports

Semi-intensive shrimp production in Honduras is based upon use of formulated diets to supply nutrients for shrimp growth. Unconsumed feed contributes nutrients to pond water, which when discharged may deteriorate water quality in receiving waters. This experiment focused on the development of nutrient budgets (nitrogen and phosphorus) in semi-intensively managed shrimp ponds receiving a low or high protein feed to 1) assess the fate of nutrients added to shrimp ponds, 2) rank the importance of nutrient sources and sinks, and 3) evaluate the potential pollutional impact of specific pond management systems. Eight 1.67-ha earthen ponds located on a commercial shrimp farm on a riverine estuary of the Gulf of Fonseca, Honduras, were used for this dry-season study. Two treatments (20% and 30% protein feed) were tested using a completely randomized design with four replicates per treatment. Ponds were stocked with hatchery-produced post-larval (PL) Penaeus vannamei to achieve a final stocking rate of approximately 80,000 shrimp/ha. Ponds were harvested 87 days after stocking. Gross shrimp yields and mean final weights did not differ significantly between treatments, and averaged 412 kg/ha and 490 kg/ha, and 6.1 g and 5.7 g for the 20% and 30% protein feed treatments, respectively. Total nitrogen and phosphorus, chlorophyll-a and BOD2 concentrations in inlet water were significantly lower than in pond water. However, no significant differences were detected between treatment water quality means. Significantly greater quantities of nitrogen and phosphorus were added to ponds as feed in the 30% protein feed treatment. Feed accounted for 41% and 52% of added nitrogen, and 47% and 55% of added phosphorus in the 20% protein and 30% protein feed treatments, respectively. Inlet water, either from the initial fill or from water exchanges and replacement, was the source of all other nitrogen and phosphorus added to ponds. Harvest of shrimp accounted for 36% to 37% of applied nitrogen and 19% to 20% of applied phosphorus. THE EFFECT OF MANAGEMENT STRATEGIES ON NUTRIENT BUDGETS: THAILAND Interim Work Plan, Global Experiment, Thailand C. Kwei Lin and Yang Yi Agricultural and Aquatic Systems Asian Institute of Technology Bangkok, Thailand James S. Diana School of Natural Resources and the Environment University of Michigan Ann Arbor, USA (Printed as Submitted)