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PD/A CRSP Research Reports 91-31 to 91-35

PD/A CRSP Research Reports 91-31 to 91-35

Techniques for assessment of stratification and effects of mechanical mixing in tropical fish ponds

James P. Szyper, University of Hawaii, Institute of Marine Biology, P.O. Box 1346, Kaneohe, Hawaii 96744

C. Kwei Lin, University of Michigan, East Lansing, Michigan 48823

3 May 1991, CRSP Research Reports 91-31

Abstract Density stratification isolates near-surface from bottom pond waters and prevents exchange of dissolved oxygen (DO) and nutrient elements, potentially restricting photosynthesis and production. Destratification strategies have become important for cost-effective intensification of pond aquaculture. Evaluation of methods and devices has emphasized effects on production, with little detailed description of effects on physico-chemical components of pond ecosystems.

This paper describes short-term effects of mechanical mixing on temporal and spatial distribution of temperature and DO in tropical freshwater fish ponds. Intensely stratified ponds of 1.5 m depth were monitored at eight depths for temperature and two depths for DO every 30 min with a modest-cost automated system of commercially available hardware. Results are presented as time-series plots, isotherm diagrams of temperature distribution with time and depth, and a stability index of energy required to mix a pond to uniform temperature.

Required mixing energy is minuscule compares with electrical energy consumption of the lowest powered mixing devices discussed in literature. Strategy for application of mechanical energy to water is critical for efficiency. A relatively subtle difference between two mixing regimes (daytime mixing for one 2-h period or two 1-h periods) produced potentially important differences in temperature and DO distribution.

This abstract was reprinted from the original, which was published in Aquacultural Engineering 9 (1990) 151-165.

Nitrogen input, primary productivity and fish yield in fertilized freshwater ponds in Indonesia

Christopher F. Knud-Hansen, Ted R. Batterson, Clarence D. McNabb, Department of Fisheries and Wildlife, Michigan State University, East Lansing, MI 48824, USA

Irwan S. Harahat, Komar Sumantadinata and H. Muhammed Eidman, Institut Pertanian Bogor, Facultas Perikanan, Jalan Raya Pajajaran, Bogor, Indonesia

27 July 1991, CRSP Research Reports 91-32

Abstract Twelve 0.02-ha ponds in West Java were fertilized weekly with four levels of chicken manure (12.5, 25, 50, and 100 g dry weight/m2/week) during a 149-day growout experiment for Nile tilapia (Oreochromis niloticus) production. Laboratory leaching experiments for measuring dissolved inorganic nitrogen (DIN) release form chicken manure showed that nitrogen was released as ammonia-N, which was rapidly lost from the manure and leveled off at about 6 mg NH4-N/g dry weight chicken manure after 4-5 days. Allochthonous DIN input from both chicken manure fertilization and almost daily source-water additions ranged from 0.055 to 0.142 g N/m2/day. Source water contributed more nitrogen than manure in all but the highest fertilization treatment.

Pond averages of net primary productivity (NP) ranged from 0.54 to 2.00 g C/m2/day, while gross fish yield at harvest ranged from 4.9 to 15.7 kg fresh weight/ha/day. Net fish yield (NFY) was linearly correlated to both the dry weight sum of NP and chicken manure fertilization (r2 = 0.97) and allochthonous DIN input (r2 = 0.96). Results suggest that Nile tilapia obtained organic carbon from both primary productivity and manure-derived detritus.

DIN availability limited algal productivity at a chicken manure fertilization rate of 100 g dry weight/m2/week when microbial decomposition of manure supplied sufficient CO2. Incorporation of allochthonous DIN input into NFY increased significantly from 15.0% at the three lower fertilization rates to 25.4% at the highest loading rate. Using organic fertilizers proportionally rich in phosphorus and carbon relative to nitrogen may maintain this element's limitation of algal productivity. Efficient utilization of DIN input also may minimize total and un-ionized ammonia concentrations. In the absence of deleterious ammonia effects on survival and growth, fish yields can be readily predicted from measurements of nitrogen inputs.

This abstract was reprinted from the original, which was published in Aquaculture, 94 (1991)49-63.

Calibration and validation of TAP, an aquaculture pond water quality model

Raul H. Piedrahita, Department of Agricultural Engineering, University of California, Davis, California 95616, USA

15 October 1991, CRSP Research Reports 91-33

Abstract A computer model of water quality in aquaculture ponds (The Aquaculture Pond model, TAP) has been run for data obtained from five research sites around the world. The procedures followed for data manipulation, and the assumptions made to complete the data requirements are described. Agreement between simulated and measured dissolved oxygen values was used as an indicator of the quality of the simulations. The quality of the simulations varied between sites and in some cases between pond treatments at a given site. Possible reasons for the variations in quality of fit are discussed.

This abstract is reprinted from the original, which was published in Aquacultural Engineering, 9: 75-96(1990).

Modeling water quality in aquaculture ecosystems

Raul H. Piedrahita, Department of Agricultural Engineering, University of California, Davis, California 95616, USA

15 October 1991, CRSP Research Reports 91-34

Abstract The techniques and uses of computer models, future developments, and applications of computer modeling in aquaculture are reviewed. The general characteristics of aquaculture ecosystems are summarized from a computer modeling point of view. Various types of models of aquaculture systems are presented, including models that simulate dissolved oxygen concentration, water temperature, and other water quality variables. The models presented are reviewed from perspectives of modeling technique, model uses, data requirements, and predictive ability. Future applications of computer models in aquaculture research and commercial practice are proposed. These applications include the development of models integrated with automated data acquisition and control systems, models that simulate water temperature and water quality parameters simultaneously, and models for use in stratified ponds.

This abstract was reprinted from the original, which was published in Aquaculture and Water Quality, 1991. Volume 3 of Advances in World Aquaculture. Pages 322-362, David E. Brune and Joseph R. Romasso (eds.).

Engineering aspects of warmwater hatchery design

Raul H. Piedrahita, Department of Agricultural Engineering, University of California Davis, Davis, California 95616, USA

5 October 1991, CRSP Research Reports 91-35

Abstract Engineering considerations for the design of hatchery systems for warmwater fishes are presented in this paper. The material is presented as it relates to specific unit operations or activities in a hatchery. Topics covered include aspects of water quality, water delivery systems, impoundment types, and water conditioning. The material is generally applicable and is not specific to a particular level of technological sophistication, or investment, or to a particular species. Application of the general principles mentioned to specific situations is dependent on the requirements for a particular installation.

This abstract was reprinted from the original, which was published in Aquaculture Systems Engineering, Proceedings of the World Aquaculture Society and the American Society of Agricultural Engineers, 1991 World Aquaculture Society, Baton Rouge, LA, USA. p. 85-100.

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