Polyculture of Penaeid Shrimp in Brackish Water Ponds Receiving Power Plant Cooling Water
Penaeid white shrimp Penaeus setiferus and blue shrimp P. stylirostris and striped mullet Mugil cephalus were cultured in 0.1-ha earthen ponds receiving power plant effluent from the Houston Lighting and Power Company's Cedar Bayou Generating Station near Baytown, Texas during 1978 and 1979. White shrimp were grown in polyculture with blue shrimp or striped mullet and in monoculture. No detrimental effect of either species on white shrimp was found. Blue shrimp yield greater than that of white shrimp in the same ponds. Total pond yield was increased by polyculture. An experiment was performed in which blue shrimp were stocked conventionally into ponds, or stocked in 3 temporally separated increments (staggered stocking study). A preliminary experiment was made in 1978, followed by a more expanded version in 1979. The staggered stocking method was found to increase pond yields compared to expected values from the control pond yields. No detrimental effect of staggered stocking on shrimp survival was found. Pond salinities were much lower in 1979 than in 1978, and lower growth, survival and yield were experienced. A distribution study performed in the staggered stocking study ponds revealed that blue shrimp in mixed size cultures tend to segregate by size, and that small shrimp show somewhat different distribution patterns and temporal activity patterns than large shrimp. A related aquarium study indicated that the presence of large shrimp has an inhibitory effect on feeding activity of small shrimp, but that where food is not limited, no detrimental effect of large shrimp on small shrimp growth occurs. All the organisms used also served as biological monitors of water quality. No dangerously high levels of heavy metals or pesticides were found in any of the cultured animals.