COMPARISON OF EXCHANGE AND NO-EXCHANGE WATER MANAGEMENT STRATEGIES FOR THE INTENSIVE POND CULTURE OF MARINE SHRIMP

Most of the potential and realized adverse environmental effects of sh rimp farming are associated with routine water exchange. This study co mpared shrimp production and water quality in triplicate ponds operate d with and without water exchange. No statistical differences were det ected in growth or survival among treatments, although there was a tre nd towards slightly smaller mean size at harvest and lower survival in the ponds operated without water exchange. The ponds operated with an d without routine water exchange had average production of 5,888 and 5 ,444 kg/ha per crop, respectively. Differences in harvest size and sur vival also influenced food conversion efficiency. The ponds operated w ithout water exchange had higher nutrients and biochemical oxygen dema nd (BOD) at the end of the study and, thus, discharged more nutrients and BOD in the drain harvesting process. However, the continuous disch arge from the ponds operated with water exchange probably resulted in a much larger total nutrient and BOD load to the adjacent estuary. Hea vy precipitation resulted in higher turbidity and total suspended soli ds in ponds with water exchange near the end of the study. Energy cost s were 31.5% higher for the ponds operated with water exchange than fo r the no-exchange ponds.