Showing papers on "Polyculture published in 1985"

Extensive and semi-intensive culture of prawn and shrimp in the Philippines

Abstract: Various farming systems for prawn and shrimp are compared, with emphasis on the extensive and semi-intensive culture of tiger prawn Penaeus monodon and white shrimp Penaeus indicus in monoculture or in polyculture with milkfish (Chanos chanos). The bases of comparison include pond design characteristics, stocking density, food supply, water management, average production, technical, and other major input requirements. Common factors that may influence production for each system are also discussed. It is observed that prawn and shrimp production has been mainly characterized by the extensive system. Of the 200,000 ha of brackishwater fishponds in the Philippines, about 25% (50,000 ha) are stocked with prawns and shrimps in monoculture or in polyculture with milkfish. Only a relatively small portion (less than 500 ha) of the area is utilized for semi-intensive culture. The dramatic increase in area utilization for extensive prawn production in recent years can be attributed to high market demand, increased hatchery-bred fry production, minimum technical requirements, and lower production cost and risks. The trend towards intensification among existing large fishfarms is hampered by rising capital costs for fishpond improvement and increasing operational expense and risks. However, intensification is gaining some attention and progress in limited areas, primarily to maximize utilization and production to avoid high investment cost of land for expansion. Further development and progress in the industry will be dependent on such factors as market price, availability of fry and feed at reasonable cost, supply of trained technicians, technical problems, financial situation, and economic viability of the operation.

Effects of Polyculture and Manure Fertilization on Water Quality and Heterotrophic Productivity in Macrobrachium rosenbergii Ponds

Abstract: Water quality effects of high densities of silver carp Hypophthalmichthys molitrix, grass carp Ctenopharyngodon idella, and water hyacinths Eichhornia crassipes in semi-intensive pond culture of prawns Macrobrachium rosenbergii were examined. Additional effects of isonitrogenous additions (8 kg N˙hectare−1˙week−1) of dried chicken manure and chicken broiler feed were evaluated. Excretion, grazing, and sediment resuspension by the carps stimulated phytoplankton productivity and turnover rates of microplankton, led to high early-morning dissolved oxygen (DO) concentrations, and, in the ponds fed manure, increased phytoplankton biomass. Removal of phosphorus from the water by water hyacinths led to reduced chlorophyll-α concentrations, primary productivity, and microplankton turnover, and to low morning DO concentrations: In hyacinth ponds fed chicken broiler feed, there were large percentage fluctuations in phytoplankton biomass. Additions of manure stimulated autotrophic productivity about 3.0 tim...

Spatial and temporal changes of nitrifying bacterial populations in fish ponds of differing management practices

Abstract: Practices of three types of fish farming (polyculture, monoculture and traditional) resulted in density differences of ammonia oxidizers which occurred in maximal numbers in polyculture and minimal in traditional systems. This distribution pattern was attributed to their nutrient status. The sine and cosine waves of periodic functions were a good fit with the seasonal data showing a sharp peak in winter. The correlation studies revealed that seasonal changes of ammonia oxidizers of these fish ponds were largely dependent upon pH, concentrations of different forms of nitrogen, phosphate, dissolved oxygen, organic carbon and organic matter as well as the ratio of C to N.

Growth of Anguilla anguilla in Different Densities in Out‐Door Containers with Tilapia aurea

Abstract: Growth of Anguilla anguilla at different densities in monoculture and in polyculture with Tilapia aurea were studied in conditions close]y related to a soil bottom fish-pond. Eels were stocked at densities of 25 or 50 A. anguilla m 2 (10.75 ft2) or 25 A. anguilla and 20 T. aurea per m2. Growth was more rapid than those of fish stocked at densities of 100 A. anguilla per m 2 (10.75 ft2), at low densities the average weight of the eels increased from 4 gm. (0.14 oz) to over 100 gm (3.53 oz). T. aurea, however grew at about the same rate in all experimental groups. Mortality of A. anguilla was highest in groups that had been stocked at a higher density.

Distribution pattern of sulphate reducing and thiosulphate oxidizing bacterial populations in fish ponds of differing farming managements

Abstract: The population size of SRB and TOB was enumerated at bimonthly intervals from water and sediment samples of six fish ponds (polyculture, monoculture and traditional systems) over a period of two and a half years. Density of SRB and TOB was maximal in polyculture and minimal in traditional systems of fish farming. Using sine and cosine waves of periodic functions or polynomial equations of high order, seasonal changes in the numbers of SRB and TOB were represented; the former occurred in largest numbers in summer while the latter in winter. Step wise multiple regression analysis revealed that organic carbon, organic matter, phosphate and different forms of N were important attributes to the seasonal changes of SRB and TOB in these fish ponds.