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Global Experiment and Related Investigations

IV. Abstracts of Technical Papers

A. Global Experiment and Related Investigations

Effect of Pond Management Strategy on Nutrient Budgets

Global Experiment

Honduras Team
Department of Fisheries and Allied Aquacultures
Alabama Agriculture Experiment Station
Auburn University, Alabama, USA

Ministerio de Recursos Naturales
Tegucigalpa, Honduras

Thailand Team
School of Natural Resources and Environment
University of Michigan
Ann Arbor, Michigan, USA

Agricultural and Food Engineering Program
Asian Institute of Technology
Bangkok, Thailand


PD/A CRSP pond management strategies rely on high nutrient loading rates to increase pond productivity. However, there is little information on the effect of semi-intensive pond management strategies on quality of pond effluents. Discharge of nutrient-rich pond water may result in deteriorated quality of receiving waters. Development of nutrient budgets would permit quantification of potential pollution impact of a specific pond management strategy. The objectives of the Global Experiment for this reporting period are, therefore, to develop nutrient budgets for nitrogen and phosphorus for semi-intensively managed freshwater and brackish water production ponds and to quantify the effect of pond management strategy on water and sediment quality. Two treatments, each replicated three times will be tested in each environment. Freshwater treatments for Nile tilapia (Oreochromis niloticus) consist of chemical fertilization plus commercially formulated fish ration (min. 20% crude protein) beginning on day 80 (Treatment 1) and chemical fertilization followed by commercially formulated fish ration (min. 20% crude protein) beginning on day 80 (Treatment 2). Brackish water treatments for Penaeus vannamei consist of feeding a commercially formulated shrimp ration containing 20% crude protein, (Treatment 1) and feeding a commercially formulated shrimp ration containing 30% crude protein (Treatment 2). The culture period will be 240 days for tilapia and 120 days for shrimp. Standard PD/A CRSP protocol will be followed to determine water budget, water quality, and sediment quality data. The experiment was started at the Honduras and Thailand sites.

Experimental Evaluation of Lime Requirement Estimators for Global Sites

Work Plan 7, Africa Study B

James R. Bowman and Wayne K. Seim
Department of Fisheries and Wildlife
Oregon State University
Corvallis, Oregon, USA


Low pond mud pH or pond water alkalinity are indications that lime should be applied to produce more favorable chemical environments for pond aquaculture. A number of methods are available for estimating the lime requirement. A number of workers have suggested the relationship between soil pH and soil base saturation differs with the amount of clay and organic matter present, and the mineralogy of the clay fraction. This study was designed to evaluate the suitability of several lime requirement (LR) estimators for a variety of soils from global sites. Soil samples were tested for LR and then added to beakers with 750 ml of soft water and the estimated amount of limestone. Water alkalinity was then monitored over the following 28 days. Results suggest different estimators perform better with specific soil types. Some estimators indicated lime should be added to soils already alkaline, even though water alkalinity did not increase with added lime. Additional analysis of these results is underway to identify the most suitable LR estimators for specific soil types.

Experimental Evaluation of Lime Requirement Estimators for Global Sites - Isolation Column Experiment

Interim Work Plan, Africa Study 3

James R. Bowman and Wayne K. Seim
Department of Fisheries and Wildlife
Oregon State University
Corvallis, Oregon, USA


Work Plan 7, Africa Study B was designed to evaluate the suitability of several different lime requirement (LR) estimators for different soil types by testing them in glass beakers containing soil samples, 750 ml of soft water and specific lime treatments. The present study was designed to investigate the use of artificial enclosures (isolation columns) as in-pond test units and to compare alkalinity response to liming in such enclosures with results obtained in the laboratory studies. The isolation columns (IC) were polyethylene tubes, 29 cm in diameter, secured to bottomless plastic buckets driven into the pond soils. Six columns were placed in one pond at a water depth of about 1 m. Three columns were limed according to its estimated LR; three were controls. Alkalinity response was monitored over the following 28 days. Soil samples from the same pond were added to 750 ml of similar quality water in glass beakers, along with the appropriate lime treatment and alkalinity measured over the following 28 days as a comparison with the IC model. Preliminary analysis of the alkalinity response patterns for each approach indicate alkalinities for laboratory "microcosms" and IC were similar after 28 days although the time course of alkalinity differed. Total alkalinities in unlimed isolation columns remained close to those in the open pond, while microcosm alkalinities in unlimed treatments differed from pond patterns, suggesting the columns did not greatly influence water quality dynamics.

Phosphorus Adsorption Capacity and Availability of Added Phosphorus in Soils from Aquaculture Areas in Thailand

Work Plan 7, Africa Study A

Claude E. Boyd and Prasert Munsiri
Department of Fisheries and Allied Aquacultures
Auburn University, Alabama, USA


A series of 20 soil samples were collected from aquaculture areas in 14 provinces of Thailand. Samples represented 10 soil suborders, and exhibited wide variation in physical and chemical properties. Soil samples were treated with 0, 25, 50, 100, and 200 ppm phosphorus and incubated under water- saturated conditions for one month. Results show that amounts of added phosphorus recoverable by water extraction decreased markedly as phosphorus adsorption capacity (PAC) of samples increased (r=0.88 to 0.96, P<0.01). This suggests that relative abilities of bottom soils to adsorb and release phosphorus added to ponds in fertilizers or feeds can be assessed from PAC data. Because of the importance of phosphorus adsorption by soil in regulating phosphorus availability to phytoplankton in ponds, the PAC appears to be a more useful technique than traditional phosphorus extraction methods as an index of phosphorus status in aquaculture ponds. The PAC was highly correlated with clay content of soils (r=957: P<0.01), and a knowledge of clay content will permit a rough assessment of phosphorus status. <P>

Problem Perceptions, Production Practices, and Economic Incentives for Tilapia Producers in Four PD/A CRSP Countries

Global Socioeconomic Study>

Joseph J. Molnar, Terry R. Hanson, and Leonard L. Lovshin
International Center for Aquaculture and Aquatic Environments
Auburn University, Alabama, USA


As a synopsis of the three main aspects of a larger study conducted under the aegis of the Pond Dynamics/Aquaculture CRSP, this article summarizes the main findings of a larger report that establishes how and to what extent the research is reaching institutions serving farmers in PD/A CRSP countries and whether they in turn influence the practices of fish farmers. An economic analysis of experiments featuring various combinations of inputs made in wet and dry seasons are presented. The primary contours of farmer practices and perception related to feeding, fertilizing, and marketing tilapia are summarized. The economic analysis utilizes the survey data and other information obtained from PD/A CRSP publications, interviews with participating scientists, and others to examine the economic viability of various experimental outcomes associated with several years of parallel experimentation. Economic viability was assessed with primary data obtained from PD/A CRSP scientists according to their 1983-92 work plan, and nutrient input regime testing.

Interviews were conducted with tilapia farmers in four PD/A CRSP countries: Rwanda, Honduras, Thailand, and the Philippines. In Rwanda, 21 active Rwandan fish farmers in eight local administrative districts (communes) were interviewed in the Kinyarwanda language during the winter and early spring of 1992. Data were obtained in Spanish from a sample of 51 active Honduran fish farmers in nine of 15 Honduran departments during the fall 1993. Data were obtained from a sample of Philippine fish farmers in four of 15 provinces on the main island of Luzon during winter 1994. The survey was revised and adapted in English; some interviews were conducted in the Tagalog language. Data were obtained in Thai language interviews with 51 active fish farmers in three of 75 Thai provinces during winter 1994.

The institutional connections of the PD/A CRSP were profiled using information obtained in published documents and from interviews and other fieldwork conducted during visits to each country. Based on information obtained from PD/A CRSP scientists, host country counterparts, and other knowledgeables, the institutional context and connections of the research program is portrayed.

Tilapia growers in each of the countries face vastly different institutional systems supporting tilapia production. Where PD/A CRSP activities have the opportunity to influence host country governmental assistance to aquaculture, efforts should emphasize infrastructure and improved functioning of the private sector. Poorly organized fish product markets and input distribution systems often hinder aquaculture development. As markets for tilapia expand, production and support services demand will also expand. Development of private sector marketing services for both production inputs and fish outputs are needed for sustained aquacultural development. Weak connections to the farm level characterize the institutional context in each PD/A CRSP country. Thus, efforts to enhance the transfer and utilization of PD/A CRSP research results will require greater attention to actual and potential pathways of influence and information flow to the farm and village. Better understanding of these relationships will facilitate the conduct of a research program that meets farm-level needs in an environmentally and socially sustainable way.

Central Data Base

Hillary Berkman

Summary of Activities

At the time the Central Data Base was transferred to the University of Hawaii it was complete through the Fourth Work Plan and nearly complete through the Fifth Work Plan. Since then data from two experiments in Rwanda and two experiments in Thailand were added to the Fifth Work Plan data.

The Sixth Work Plan included 19 experiments to be conducted between September 1, 1991 and August 31, 1993. Supplemental Work Plans included nine more experiments to be conducted during that period. All data collected using standard CRSP methods, and which the database could accommodate, were to be reported. (See Sixth Work Plan, page 1). Currently, the CRSP data base includes the following Sixth Work Plan data: two experiments from Honduras, three experiments from the Philippines and five experiments from Thailand. There are no data from Rwanda reported in the data base. In summary, ten experiments from the Sixth Work Plan have been included in the data base.

The Seventh Work Plan experiments covered the period from September 1, 1993 to August 31, 1995. Nine experiments were to be conducted in Honduras; none are reported in the database. Ten studies were to be conducted in Thailand; the results of four of those studies are included in the data base. Two experiments from the Philippines are reported. No data from Egypt are included in the database. Rwanda data are understandably absent. In summary, six experiments from the Seventh Work Plan have been added to the database.