BRACKISH WATER POND POLYCULTURE OF ESTUARINE FISHES IN THERMAL EFFLUENT

Abstract

AbstractThree species of fish were cultured in 0.1 ha ponds from August 1976 to May 1977. Each pond received a constant flow of thermal effluent from the discharge canal of the Cedar Bayou Generating Station, Houston Lighting & Power Company. Striped mullet (Mugil cephalus) were maintained in polyculture with black drum (Pogonias cromis) and Atlantic croaker (Micropogon undulatus). These fish were also raised in mnoculture. Survival of mullet in polyculture with drum averaged 91.8%; in polyculture with croaker, 96.4%; in monoculture, 96.8%. Black drum survival averaged 95.5% in polyculture and 96.3% in monoculture. Croaker survived slightly better in monoculture at 39.3% compared to 33.5% in plyculture with mullet. Poor croaker survival was attributed to low cool season temperatures and handling mortalities. Growth of all species was improved in polyculture. Mean daily length and weight gains for mullet in monoculture were 0.22 mm/day and 0.35 g/day. These increased to 0.25 mm/day and 0.46 g/day in polyculture with drum, and 0.26 mm/day and 0.60 g/day in polyculture with croaker. Similarly, rates for black drum increased from 0.39 to 0.41 mm/day and from 0.76 to 0.90 g/day when raised with mullet. Monocultured croaker grew 0.21 mm/ day and 0.60 g/day, while in polyculture with mullet these increased to 0.28 mm/day and 0.69 g/day. Competition values indicated that daily yield of mullet and black drum was increased 30% and 20% respectively through polyculture. Growth of croaker was largely unaffected by addition of mullet into the system, but mullet growth was raised 78% through this association. Thermal additions to these ponds proved critical when seasonal grmth trends were examined.