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Global Studies and Activities

B. Global Studies and Activities

Minding the Pond: Feeding, Fertilization, and Stocking Practices for Tilapia Production in Rwanda, Thailand, The Philippines and Honduras

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


This report provides basic descriptive information concerning the way aquaculture is practiced in four CRSP countries. It focuses on four central aspects of tilapia culture; pond management, feeding, fertilization, and stocking practices. Data were collected from tilapia growers: 121 active Rwanda fish farmers in eight local administrative districts (communes) during the winter and early spring of 1992; 51 active Honduran fish farmers in five of 15 Honduran departments during the fall 1993; 51 active Thai fish farmers in four of 75 Thai provinces during winter 1994; 56 Philippine fish farmers in four of 15 provinces on the main island of Luzon during winter 1994. In each country, the survey instrument was revised and adapted, then translated into the national language. More than 80 percent of the Rwandan farmers had but a single pond. In contrast, more than 70 percent of the Philippine and Honduran farmers had more than one pond. Most Honduran farmers had more that a hectare of ponds. More than half the Thai sample reported problems getting enough water to keep ponds full. A third of the Philippine farmers said so, as did a quarter of the Rwandans. Farmers in the four countries fed their tilapia a variety of different items reflecting differences in the intensity of aquaculture practice in each nation. Commercial feed was not used in Rwanda; two-thirds of the Hondurans did not use commercial feed; and about half the Philippine respondents did not use commercial feed. Thai farmers were most dependent on commercial inputs to raise their tilapia crops. They also used the most diverse variety of feeds, reflecting the high level of availability of different feed types and a greater willingness to use feeds for other animals for the fish as well. Honduran and Rwandan farmers were most likely to report inadequacies in feed availability on their farms. About seven percent of the Rwandan farmers said that they never had enough. Cattle and goats were most often reported in Rwanda, pigs in Honduras, and chickens in the Philippines, and ducks were more frequent on Thai farms. Given the pervasive use of integrated systems in Thailand, ponds are most frequently fertilized by animal manure in that country. Thai farmers also are more likely to apply lime to improve the alkaline balance of the pond and foster primary productivity. Rwandan farmers indicated the most passive approach to fish farming - about half said they visited every day. Philippine farmers spent the most time with their ponds when they visited them; Thai farmers the least. Fingerling availability was a problem for 30 percent of the Philippine respondents, less than 25 percent in Rwanda and Honduras, and a concern for only 4 percent in Thailand. Most farmers are growing but single crop of tilapia each year in Rwanda and Thailand. In Honduras, almost half reported two or more crops, but in the Philippines two-thirds obtained two crops per year. The data emanating from this study present a comparative perspective on tilapia culture in four CRSP countries. The similarities and differences suggest different patterns of technology utilization and need in each setting. The benefits of these understandings should help shape research directions and enhance the development impacts of CRSP technologies.

POND: A Decision Support System for Pond Aquaculture

John P. Bolte, Shree S. Nath, and Doug E. Ernst
Department of Bioresource Engineering
Oregon State University
Corvallis, Oregon, USA


Decision support systems are a useful mechanism for synthesizing qualitative and quantitative knowledge into analysis tools that can easily be used by a diverse audience. A user-friendly decision support system (POND) which can be used to guide decision-making processes relevant to pond aquaculture management and planning has been developed. POND uses a combination of expertise, an economics package, and simulation models for analyzing pond aquaculture systems, either at the level of an individual pond or for an overall facility. This functionality is accomplished by the use of an object-oriented paradigm which enables the definition of objects responsible for certain tasks analogous to entities or experts in a real pond aquaculture facility (e.g., a fish culturist) responsible for monitoring fish growth). The economics package can be used to generate enterprise budgets, which account for fixed and variable costs, depreciation, interest, and income items. Users can examine various pond management strategies and generate enterprise budgets to assess the economic viability of such strategies.POND includes simulation models to describe the dynamics of fish growth, water temperature, carbon, nitrogen and phosphorus, phytoplankton, and zooplankton. These models are organized hierarchically into two levels to provide users with the capability of performing different kinds of analyses based on data availability and output resolution needs. The fish growth model accounts for the effects of fish weight, food availability, photoperiod, temperature, and dissolved oxygen and unionized ammonia concentrations, and has been calibrated for Nile tilapia. This model has been used to simulate PD/A CRSP experiments at different sites with favorable results. Simulation models that are used in POND to describe other state variables are briefly discussed.