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Mixed-sex blue tilapia Oreochromis aureus fry were produced from indoor spawns in March and April. Fry were stocked in May at an average weight of 0.5 g at 0, 250, 750, or 2,500/ha into ponds which had been stocked previously with three catfish strains at a combined density of 10,000 fingerlings/ha. After a 167-d culture period, from 15 May until 4 November, tilapia stocked at 250 or 750/ha grew to average harvest size approaching 0.45 kg. No significant difference in average size was observed between males and females except at the 2,500 tilapia/ha stocking density. Sixty percent of the tilapia polyculture ponds yielded no reproduction at harvest and maximum reproduction observed was 13.5 kg/ha. Lack of reproduction and the undeveloped state of sampled female ovaries indicated that most females had yet to attain sexual maturity. Catfish production and catfish feed conversion was not significantly different between tilapia polyculture and catfish monoculture ponds (P > 0.05). First seine hauls yielded over 88% of the total catfish harvest, but only an average of 3.9% of the marketable tilapia. Tilapia had no measurable impact on the incidence of catfish off-flavor at any of three sample intervals. Overall average levels of TAN and nitrites did not differ significantly between treatments; however, mean chlorophyll a concentration was significantly higher (P > 0.05) in the 2,500 tilapia/ha treatment than at lower tilapia densities.

We tested an airlift-operated floating raceway in which fry of channel catfish (Ictalurus punctatus) were raised from swim-up stage to 5 cm total length (TL) before stocking into rearing ponds. Survival of fry raised in this manner was compared with that of swim-up fry stocked directly into rearing ponds. Swim-up fry stocked into two 1.87-m3 floating raceways at a density of 21,390 fry/m3 (40,000 fry/raceway) grew to 5 cm TL within 27 d and had an average survival of 90.3%. When these fry were subsequently stocked into two 0.2-ha ponds for further rearing, 95.2% survived to 12.5-cm fingerling size. Overall, survival from swim-up stage averaged 86.1%. Survival in ponds stocked with swim-up fry averaged 84.1%. Unaccounted fish losses during the pond-rearing phase were lower in ponds stocked with raceway-reared fry than in ponds stocked with swim-up fry (4.1% versus 14.7%, respectively). Although overall survival of raceway-reared and pond-reared groups was similar, the floating raceway system offer...