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Research Summary - 19th Administrative Report
PD/A CRSP Nineteenth Annual Administrative Report

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Research Summary

Research Area: Production Optimization
Research Theme: Pond Dynamics Research

9PDR2/Pond soil characteristics and dynamics of soil organic matter and nutrients/Boyd [Final report]

For years aquaculturists have largely ignored bottom soils, but as levels of production have increased, it is apparent that bottom soils are an important factor in pond dynamics. During the Eighth and Ninth Work Plans, soil cores were obtained from ponds at PD/A CRSP sites in Thailand, Honduras, Kenya, Peru, and the Philippines and non-CRSP sites in Brazil and Ecuador. The data obtained on the composition of pond sediment were used to develop a system for classifying pond soils; this report mainly describes this system. The proposed system allows pond sediment to be classified using four primary and five secondary properties, as well as two optional tertiary properties. The primary properties used were pH, texture, sediment thickness, and organic matter status (mineral or organic in nature). The secondary properties used were organic carbon, carbon:nitrogen ratio, acidity, carbonates, and sodium adsorption ratio. The two tertiary properties used were the thickness of the F horizon and the oxidation status of the sediment surface; these may be used for classification when desired. Results from the pond soil studies also revealed information such as: reactions between pond soil and pond water occur primarily in the upper 2 to 10 cm layer; low pH, high acidity, and elevated organic matter concentration in surface sediment appear to be the most common chemical problem with pond soils; and accumulation of soft sediment in ponds is the most common physical problem with pond soils. These observations suggest that pond bottoms should be dried between crops and that ponds should be limed in order to reduce acidity and increase pH levels. It is anticipated that these findings will greatly improve pond soil management practices.

Research Area: Production Optimization
Research Theme: Feeds and Fertilizer Research

9FFR2/Growth performance and economic benefits of Oreochromis niloticus/Clarias gariepinus polyculture fed on three supplementary feeds in fertilized tropical ponds/Bowman [Final report; report title different than study title in Ninth Work Plan]

High-quality, nutritionally complete supplemental feeds produce high fish yields; however, this strategy is often impossible or inappropriate in countries where high quality feedstuffs are limited. In Africa, nutritionally complete diets for tilapia are very expensive, and poultry and bran diets are often substituted, both of which are nutritionally unbalanced. This experiment examined appropriate feed/fertilizer combinations for tilapia in order to increase natural food organisms in ponds and ultimately improve production. Three low-cost supplemental feeds were tested: rice bran, a commercially available pig finisher pellet, and a formulated,
test-diet pellet. Fertilizer regimes were the same for all three diets, consisting of application of diammonium phosphate and urea. Results showed the locally available pig finisher pellets was the most profitable.

Research Area: Production Optimization
Research Theme: Feeds and Fertilizers Research

9FFR2A/Fish yields and economic benefits of tilapia/Clarias polyculture in fertilized ponds receiving commercial feeds or pelleted agricultural by-products/Lochmann [Final report]

Stable isotope ratios have been used to trace the assimilation of materials ingested by fish and hence estimate the relative contribution of different feedstuffs to fish growth. In this component of a related Kenya Project feeding investigation (9FFR2), stable isotope ratios of carbon and nitrogen in three test diets, plankton, and Nile tilapia were analyzed. In the feeding study, caged tilapia had access only to plankton, while free-swimming fish consumed plankton and one of three test diets. It was anticipated that as fish assimilated food with a distinctive stable isotope signature, it would be possible to estimate the contribution of each food to growth. The free-swimming tilapia (those that ate both plankton and a test diet) showed isotopic evidence of a varied diet. However, growth during the experimental period (50% of final body weight) was not high enough to distinguish the influence of assimilation of different foods.

Research Area: Production Optimization
Research Theme: Feeds and Fertilizers Research

9FFR3/Reduction of feed rations below satiation levels in tilapia pond production/Brown [Final report; report title different than study title in Ninth Work Plan]

An important goal of CRSP feeds and fertilizers research is to optimize the economic benefits of all pond inputs. The use of supplementary feed in addition to fertilization has improved tilapia yields economically, but while using commercial feeds ensures rapid growth of fish, feed costs often demand 60 to 70% of total production costs. Good feeding procedures are important in order to minimize feed wastage and deterioration of water quality. The goal of this study was to evaluate growth, yield, and survival for tilapia fed daily at 100 and 67% of experimentally determined satiation. Two ponds stocked with sex-reversed Nile tilapia at each of the nine participating farm sites were assigned one of each of the two treatments. All ponds were fertilized weekly with urea and ammonium phosphate at a rate of 28kg N ha-1 wk-1 and 5.6 kg P ha-1 wk-1, and water quality parameters were monitored monthly using standard methods. A sample of 50 fish was obtained from each pond every month to measure average weights of the fish. After 120 days, the ponds were harvested and the total number of fish were counted and bulk-weighed. Results at harvest showed that there were no significant differences found in mean weights, daily weight gains, fish yields, extrapolated gross yields, and survival between the two satiation levels tested. Fish fed at the reduced satiation level displayed a better feed conversion ratio than those fed at full satiation, and the reduction in the amount of feed used amounted to about US$400 savings in terms of feed costs. The results of this study may be readily accepted by tilapia farmers who seek to reduce production costs without compromising yields or quality.

Research Area: Production Optimization
Research Theme: Feeds and Fertilizers Research

9FFR5/Educational development activities in support of tilapia aquaculture in the Philippines/Brown [Final report; report title different than study title in Ninth Work Plan]

The objective of this activity was to further the formal education and training of a graduate student in the Aquaculture masters or doctoral program at the Freshwater Aquaculture Center of Central Luzon State University (CLSU) and to improve the capabilities of aquaculture teaching laboratories at this facility. During the time of this activity, graduate student Eddie Lopez was supported during the concluding stages of his doctoral studies. The student's research, including descriptive and experimental components, investigated the interactions of growth, survival, and social behavior of genetically manipulated tilapia. In addition, improvements of facilities at CLSU were made, including the construction of 15 concrete tanks for student and faculty research. A Fisheries Information and Learning Center is also being set up to catalog and maintain various aquaculture and fisheries references. The improvements should benefit all students and faculty at the Freshwater Aquaculture Center at CLSU.

Research Area: Production Optimization
Research Theme: Feeds and Fertilizers Research

9FFR6/Development of training modules for aquaculture extension workers and university students in Kenya/Bowman [Final report]

Lack of technical training is a major reason for the low output of fish ponds in Kenya. The objective of this activity was to increase the capability of the Department of Fisheries at Moi University (MU) in order to improve aquacultural practices in the region. This activity provided funds and mentoring to allow one faculty member from the MU Department of Fisheries to travel to Auburn University (AU) to learn technical skills needed in order to prepare training modules for use in training courses in Kenya. Charles Ngugi of MU spent about eight weeks in the US developing three complete training modules including: Introduction to Aquaculture­An Overview, Pond Construction­Site Selection, and Pond Management and Maintenance. Ngugi also began work on a number of other modules, which will be adaptations of existing modules for the Kenya region. The activity has also provided MU faculty with improved computer and course preparation skills, which will lead to the development of better training materials and the more thorough dissemination of information to extension workers and university students in the region.

Research Area: Production Optimization
Research Theme: Reproduction Control Research

9RCR5C/Masculinization of tilapia by immersion in trenbolone acetate: Detection of trenbolone acetate in water after treatment/Schreck [Final report]

Masculinizing Nile tilapia fry by immersion can be a good alternative to feeding the fry with food containing hormones, posing fewer risks to hatchery workers and the environment. Previous experiments have found that two 3-hour immersions in trenbolone acetate (TA) can successfully masculinize Nile tilapia fry. This experiment investigated the change in concentration of TA in the immersion water before and after treatment to determine the amount of hormone to use and to estimate the potential to reuse the treatment water. Nile tilapia were immersed twice for three hours in the steroid, then collected and sent to a laboratory for examination. Results showed that TA concentrations were highly variable at all times, indicating that a target dose for TA immersion is rarely achieved. The low concentrations of TA found in the treatment water before the fish immersion may explain the lack of masculinization that happened during this experiment. Results also showed that the steroid was present in the water even after the fish had been immersed, which suggests that reuse of the treatment water for consecutive treatments may be an improvement on this technique.

Research Area: Production Optimization
Research Theme: Reproductive Control Research

9RCR5D/Masculinization of Nile tilapia fry by immersion in trenbolone acetate: Reuse of hormone solution and effects of temperature/Schreck [Final report]

If a technique were developed that could consistently masculinize tilapia fry using short-term treatments while presenting little or no risk to the environment, it could potentially replace the current method of administering hormones to fish through the diet, in which uneaten steroids accumulate in the pond sediment and eventually contaminate the water. Preliminary studies have shown that short immersions in the synthetic androgen trenbolone acetate (TA) may be a good way to masculinize Nile tilapia fry. TA is a synthetic steroid that is widely used in the cattle industry to enhance growth and is considered to be a very potent masculinizing agent. The objectives of this study were to 1)determine if masculinization of Nile tilapia fry by immersion in synthetic steroids is efficient in large-scale systems, 2) evaluate if the interaction of immersions with elevated temperatures improves masculinization rates, and 3) evaluate the potential for reuse of steroid solutions used in immersions. Fry were immersed twice for three hours each in the TA. Results showed that there were significantly more males in the groups treated with TA (55.9 and 61.6%) than in the control groups, but the amount of males was still far below the percentage of males recommended for aquacultural purposes. When the TA was reused, the treatments did not produce a significant number of males. Results also showed that elevating temperatures in combination with TA treatments did not result in a greater number of males. More research is needed to investigate immersion protocol and hormone treatments for masculinization.

Research Area: Production Optimization
Research Theme: Reproductive Control Research

9RCR6A/Monosex tilapia production through androgenesis: Selection of individuals for sex inheritance characteristics for use in monosex production/Phelps [Final report]

One of the goals of CRSP reproduction control research is to develop short- and long-term solutions to reproduction technology problems. If tilapia reproduction is not controlled during the culture period, there will be few or no marketable fish after six months. All-male populations are preferred and can be created using hormone sex-reversal, but some consumers have concerns about eating hormone-treated fish. Inter- and intraspecific breeding programs can also result in populations high in males but give inconsistent results. Sex inheritance in Nile tilapia does not conform to a 1:1 ratio of females to males, as would be expected from a simple Mendelian XX:XY sex determination process. This study used cross-breeding among and within nine families of Nile tilapia to determine a true-breeding tilapia strain. Results from the 88 spawns collected showed that sex ratios did not appear to be passed on from one generation to another. The offspring from sibling mating within each family had a wide range of sex ratios from 19 to 86% male, and no family with skewed sex ratios produced offspring with similarly skewed ratios. This lack of consistent sex ratios in the offspring provided evidence that a YY breeding program to produce all-male offspring in Nile tilapia is not likely to succeed.

Research Area: Production Optimization
Research Theme: Reproductive Control Research

9RCR7/Monosex tilapia production through androgenesis/Shelton [Final Report]

As part of a five-year effort to produce all-male tilapia populations without the use of steroids, this investigation was designed to examine the mechanism of sex determination in Nile tilapia and to develop a chromosome manipulation protocol for the production of progeny with only a paternal genome. However, the severe temperature and UV shocks necessary to accomplish ploidy manipulation resulted in very high mortality, and none of the androgenotes survived to maturity. The lack of survival of androgenotes, combined with ongoing uncertainty as to the mechanism of sex determination in tilapia, indicated a likelihood of continued failure. Thus, the study was terminated.

Research Area: Production Optimization
Research Theme: Reproductive Control Research

9RCR8/The application of ultrasound to produce all-male tilapia using immersion protocol/Diana [Final Report]

This investigation sought to increase the efficacy and efficiency of masculinizing hormones in producing all-male populations of tilapia. In efforts to control unwanted reproduction of tilapia and because males are preferred since they grow faster than females, the practice of masculinizing tilapia has been developed using various types of hormones. Current methods of masculinizing tilapia populations include adding hormones into feed; however, hormones are unevenly distributed to the fish and potentially unsafe
because the hormone-containing feed dissolves in water over time. Immersion of fish in hormone-containing solution has also been practiced to masculinize tilapia. This study explored the use of ultrasound to improve the effectiveness of immersion. Three experiments were carried out to evaluate variation in hormone type and dosage, duration of exposure, and influence of cavitation-level ultrasound. The first experiment used treatments in one- and two-hour durations to assess the effects of two hormones at concentrations of 100 and 500 mg l-1. Results indicated that two-hour immersion combined with ultrasound produced consistently larger percentages of males than one-hour treatments. The second experiment repeated the procedures of the first experiment, except that it used three replicates per treatment, used a lower MT dose of 50 mg l-1, and tested the hormones MDHT and TBA at 100 and 250 mg l-1. The experiment illustrated that all three hormones are potent masculinizers of tilapia, but results were clouded by high mortality due to a bacterial infection in the pond. In order to verify the results from the second experiment, a third experiment was carried out using only MDHT and TBA at two concentrations (100 and 250 mg l-1), and with or without ultrasound treatments. Results showed that TBA at 250 mg l-1 with ultrasound was the most effective hormone in consistently producing a large percentage (98 to 100%) of male tilapia.

Research Area: Production Optimization
Research Theme: New Aquaculture Systems/New Species Research

9NS1/Lotus-fish culture in ponds: Recycling of pond mud nutrients/Diana [Final report]

Regular feeding and fertilization in fish ponds encourages the accumulation of nutrients, especially phosphorus, in pond mud. Pond muds have been used to fertilize land crops; however, removing pond mud is labor intensive, and its practicability is questionable. Aqueous macrophytes, like lotus, may be better able to utilize the phosphorus found in the pond soil. This experiment examined whether the alternative practice of lotus-fish culture can better recover these deposited nutrients. Ponds were cultivated with fish alone, lotus alone, and fish and lotus together. Fish were stocked at 2fish m-2, and lotus plants were stocked at 20 plants per 200-m2 pond. Treatment ponds stocked with tilapia were fertilized weekly at rates of 28 kg N and 7 kg P ha-1 wk-1; no fertilizer was applied in ponds with lotus alone. Results showed that lotus co-cultured with tilapia or alone in ponds effectively took up nutrients in old pond mud by about 2.4 t N and 1 t P ha-1 yr-1. Nile tilapia cultured alone grew significantly better than those co-cultured with lotus, while there was no significant difference in lotus growth between treatments. Since dead lotus leaves were not removed from the ponds, the shading effect of the leaves could have caused the slow growth and higher morality of tilapia in the lotus-tilapia co-culture system in this experiment. The experiment showed an effective way to remove nutrients from old pond mud using lotus plants and to feasibly rotate or co-culture lotus and Nile tilapia; however, more research is needed to refine the system and make it more profitable.

Research Area: Production Optimization
Research Theme: New Aquaculture Systems/New Species Research

9NS2/Culture of mixed-sex Nile tilapia with predatory snakehead/Diana [Final report]

Intensive culture of Nile tilapia often leads to overpopulation in ponds, resulting in a shortage of food for the fish, which stunts their growth. In areas where all-male tilapia populations cannot be produced, predation of tilapia offspring may prove an effective means of controlling reproduction. Predators such as snakehead (Channa striata) have been reported as effective in reducing population numbers. This experiment examined the efficiency of snakehead in controlling tilapia reproduction and their effect on tilapia growth and production. The experiment included six treatments: monoculture of sex-reversed all-male tilapia, monoculture of mixed-sex tilapia, and polyculture of snakehead and mixed-sex tilapia at stocking ratios of 1:10, 1:20, 1:40, and 1:80. Results showed that snakehead were able to completely control overpopulation of Nile tilapia at the low predator:stocked-prey ratio of 1:80; however, considering all growth parameters, the best predator: stocked-prey ratio was 1:20. All of the predator treatments were profitable, and the mixed-sex culture produced significantly higher net return than the sex-reversed culture. Polyculture at the lowest ratio of 1:80 showed the highest net return, followed by the 1:20 ratio. Results also showed that while adding snakehead into Nile tilapia ponds did not result in significantly greater tilapia growth, it did lower total net and gross yields of tilapia recruited (but only compared to mixed-sex fish).

Research Area: Production Optimization
Research Theme: New Aquaculture Systems/New Species Research

9NS3 and 6/Development of sustainable pond aquaculture practices for Colossoma macropomum and Piaractus brachypomus in the Peruvian Amazon [Final report; report title different than investigation title in Ninth Work Plan]

The culture of two species native to the Peruvian Amazon, Colossoma macropomum (gamitana) and Piaractus brachypomus (paco), form the basis of Peru Project research. Previous investigations into stocking density were continued, with paco tested at 4,000, 6,000, and 8,000 fish ha-1; all three densities were shown to be economically viable, and the highest stocking density was the most profitable. Gamitana, with similar culture costs and market value 50% higher than that of paco, is even more profitable, although either species cultured at any density tested showed more profit potential per hectare than pineapple, the next most profitable agricultural product in the region. A second component of the study examined reproduction of the two species. A hormone, LHRHa, was identified as successful in inducing spawning of paco. Gamitana was not successfully induced to spawn. Additional components involved training technicians in laboratory and pond practices, producing a Spanish-language manual on reproduction of paco and gamitana, and conducting outreach activities to regionalize the results of CRSP Peru Project research.

Research Area: Production Optimization
Research Theme: New Aquaculture Systems/New Species Research

9NS3A/Spawning and grow-out of Colossoma macropomum and/or Piaractus brachypomus/Lochmann [Final report]

Colossomid broodstock cultures in Iquitos, Peru, are limited by the inability to spawn consistently, which may be caused by inadequate nutrition. This study analyzed broodstock feedstuffs and diet in order to make recommendations for nutrition to maximize spawning. Results showed that the energy:protein ratio is too low in the broodstock diet, causing the fish to metabolize for basic maintenance requirements protein needed for gamete production. These results also revealed that there is an apparent lack of lipids in fertilized colossomid eggs. Both of these problems can be solved by supplementing the diet with additional lipids. Studies have found that a 1:1 ratio of n-3 to n-6 fatty acids is optimal for most fish functions, including reproduction; however, colossomid eggs in this study appeared to have twice as many n-3 fatty acids as n-6 fatty acids. This condition could impair spawning and lower gamete and larval quality, as it has been known to do in other fish species. Since the main source of these fatty acids in the current broodstock diet is fish meal, it is recommended that a combination of fish meal and soybean meal be used to meet the fish's amino acid requirements. Fish should be fed diets containing eight to ten times the level of vitamin C required for optimal growth to increase the quality of their eggs. Both vitamins C and E should be supplemented in stabilized forms to prevent deterioration under conditions of high heat and humidity found in Iquitos. This study also examined carotenoids, but further research is necessary to identify an inexpensive source that could be used in Iquitos.

Research Area: Production Optimization
Research Theme: New Aquaculture Systems/New Species Research

9NS4/Semi-intensive culture of red tilapia in brackishwater ponds/Diana [Final report; report title different than investigation title in Addendum to the Ninth Work Plan]

Many tilapia species, including Thai red tilapia, are capable of tolerating a wide range of salinities and can successfully grow in brackish water after proper acclimation. However, information on semi-intensive tilapia culture in saline ponds is almost nonexistent. In Thailand, shrimp culture is commonly reduced to one crop per year, leaving the ponds empty for large portions of the year, or in some cases the ponds have been abandoned due to failure of shrimp farming. The objectives of this experiment were to 1) determine appropriate fertilization regimes in brackishwater ponds, 2) investigate nutritional value and digestibility of marine phytoplankton, and 3) exploit underutilized or abandoned shrimp ponds for tilapia production. This experiment tested two fertilization regimes (28 kg N and 7kg P ha-1 wk-1, N:P = 4:1, and 14 kg N and 7 kg P ha-1 wk-1, N:P = 2:1) and three salinity levels (10, 20, and 30). Results showed that Thai red tilapia grew better in brackishwater ponds than in freshwater ponds in semi-intensive fertilization culture systems, with the best growth performance and highest net return from ponds fertilized with the N:P ratio of 2:1 at 10 salinity. These data provide farmers of the coastal zones of Southeast Asia with a low-risk use of their shrimp ponds.

Research Area: Production Optimization
Research Theme: New Aquaculture Systems/New Species Research

9NS5/Supplemental feeding for semi-intensive culture of red tilapia in brackishwater ponds/Diana [Final report]

Developing alternative aquaculture systems to aid in the use of underutilized resources is an important goal of new aquaculture systems research. A large number of shrimp ponds in Southeast Asia and Central and South America are left underutilized or abandoned due to failure of shrimp farming or the farmer's desire to diversify shrimp culture. The purpose of this experiment was to determine appropriate levels of supplemental feeding in fertilized brackishwater ponds for maximum growth of red tilapia and to provide farmers with a cost-effective alternative to leaving their shrimp ponds empty. Five different supplemental feeding regimes consisting of 0, 25, 50, 75, and 100% of satiation were tested. Red tilapia fingerlings were stocked in 15 net cages suspended in an earthen pond and cultured for 90 days. The pond was maintained at 10 salinity and fertilized weekly at rates of 4 kg N and 1 kg P ha-1 d-1. Results showed that growth and yield of the tilapia increased significantly with increased feeding rates from 0 to 75% satiation, while there were no significant differences between 75 and 100% of satiation. The feed conversion ratio was significantly better with lower percentages of satiation feeding, and total weight gain of the tilapia was linearly and positively correlated with total feed input to cages. Partial budget analysis indicated that supplemental feeding at 25 to 75% satiation was profitable for red tilapia, but 50% satiation feeding was the most efficient rate.

Research Area: Environmental Effects
Research Theme: Effluents and Pollution Research

9ER2D/Fate of methyltestosterone in the pond environment: Use of MT in earthen ponds with no record of hormone usage/Schreck [Final report]

This is the fourth phase of an investigation examining the fate of 17a-methyltestosterone (MT) used to masculinize Nile tilapia fry in the pond environment. The first two phases found that MT persists in soil for up to eight weeks after treatment termination in model and actual ponds. The third phase found that MT in soils in model ponds had little masculinizing effect on fish. This final phase examined the buildup and persistence of MT in soils in a pond in Mexico used for masculinizing fry. MT was not detectable in water at any point in the trial and was detected in soils only after 10 days of administering MT-treated feed to fry. MT concentration did not correlate with proximity to feeding location nor did it gradually increase over time. Bacterial degradation of the steroid and patchiness due to uneven food deposition or mixing may have contributed to the variable MT levels. Another component of this investigation was the production of a Spanish-language manual on safe and effective use of MT to masculinize fry.

Research Area: Environmental Effects
Research Theme: Effluents and Pollution Research

9ER4/Effects of water recycling on water quality and bottom soils in shrimp ponds/Boyd [Final report; report title different than investigation title in Addendum to the Ninth Work Plan]

Shrimp aquaculture pond water can become overly rich in mineral and organic nutrients when excessive amounts of fertilizer and feed are used to produce shrimp, and water quality can be compromised. A conventional practice to replace degraded water in shrimp ponds is to exchange the old water with cleaner water, but the effluents can have negative impacts on receiving waters. An alternative to water exchange may be to recycle pond water in an oxidation pond. This study evaluated changes in chemical characteristics of pond water, soils, and shrimp yields in response to water recycling. Results showed no differences in water quality between ponds with recycled water and ponds without it. Also, no differences among treatments were observed for soil pH; concentrations of carbon, sulfur, and nitrogen; soil respiration; and phosphorus absorption capacity. It was concluded that recycling water from a production pond through an oxidation pond of equal volume had minimal to no effect on water quality or shrimp yields.

Research Area: Environmental Effects
Research Theme: Appropriate Technology Research

9ATR1/On-farm trials: Evaluation of alternative aquaculture technologies by local farmers in Kenya/Bowman [Progress report]

On-farm testing in 52 ponds, with 30 participating farmers, was conducted in Kenya's Central Province to determine whether research-based technologies are directly transferable to the farm, as well as to help farmers and extension agents understand stocking strategies and pond management options. A three-fold increase in production was obtained, and farmers were able to evaluate technologies and make informed decisions about increasing fish production in their own ponds under local conditions. The trials also allowed project personnel to train fisheries extension agents, thereby complementing the training they will receive through other Kenya Project activities.

Research Area: Environmental Effects
Research Theme: Appropriate Technology Research

9ATR2/Linkages of aquaculture within watersheds and concurrent design of hillside ponds/Verma [Final report]

The hillsides of Central America and the Andean region cover about 1 million km2 and provide livelihood for some 20 million people, half of whom are small-scale farmers living in marginalized, rural communities. Introducing tilapia production to the hillside regions of Central America could improve nutrition and provide additional income for farm families and local communities. A levee pond design model was developed for extension personnel to use as they assist local producers in building hillside ponds. The levee pond model is an Excel, spreadsheet that computes a volume balance on a levee pond. The model can compute the inflow of water needed to balance net seepage and evaporation and can determine the pump-in and pump-out rates needed to reach a target volume change per month. A spillway design is also provided based on an empirical spillway design approach. The model is currently in verification and testing and is expected to benefit locations previously determined to have market potential.

Research Area: Social and Economic Aspects
Research Theme: Marketing and Economic Analysis Research

9MEAR3/Development of Central American markets for tilapia produced in the region/Engle [Final report]

Virtually no research has been done on the potential to develop domestic markets for tilapia in Central America. If markets are not expanded and developed, increased production of tilapia will result in declining prices, having a negative impact on Central America's tilapia industry. The objective of this activity was to conduct an analysis of potential Central American markets for tilapia and to develop marketing strategies for tilapia produced in the region. Surveys of supermarkets, fish markets, and restaurants were conducted between 1999 and 2000 in both Honduras and Nicaragua in order to characterize each outlet in terms of business, clientele, and types of fish sold. Questions specifically about tilapia included volumes, prices, suppliers, product forms, supply problems, and market channels used. Results from the Honduras surveys showed that tilapia is a well-known product and that tilapia sales have increased in recent years. Reasons for not selling tilapia included availability problems, lack of demand, and freshness problems. Negative ratings of tilapia by some respondents may have to do with the poor quality of wild-caught tilapia also sold in the markets. Strategies to improve domestic markets in Honduras should include offering catch-of-the-day promotions in restaurants, sampling and in-store demonstrations in supermarkets, and informing consumers about the differences between wild-caught and farm-grown tilapia. Results from the surveys conducted in Nicaragua showed that open-air markets were selling less tilapia than in prior years, but supermarket surveys indicated that their tilapia sales had increased. Reasons vendors did not sell tilapia included an inconsistent supply, odor problems, and consumer fear that the fish came from Lake Managua, which is contaminated. Strategies for improving tilapia marketability in Nicaragua include developing markets in upscale restaurants and educating consumers to alleviate contamination fears.

Research Area: Social and Economic Aspects
Research Theme: Marketing and Economic Analysis Research

9MEAR4/Economic and social returns to technology and investment in Thailand/Engle [Final report]

The farm-level economic impacts of three aquaculture production technologies in Thailand were compared with the fertilization technology developed by the PD/A CRSP. Assuming adequate resources exist on the farm, the combination of intensive fertilization practices and monoculture of sex-reversed tilapia developed by the PD/A CRSP produced the most profitable technology. However, given the limited resources generally available on farms in northeastern Thailand, the optimal model would be that four out of five ponds be stocked in the extensive polyculture system and only one pond stocked in tilapia monoculture. Thus, despite the expected strong impact of PD/A CRSP technologies, the lack of operating capital common throughout the country will sharply constrain the adoption, implementation, and impact of these technologies.

Research Area: Social and Economic Aspects
Research Theme: Marketing and Economic Analysis Research

9MEAR5/Rapid economic evaluation tools/Hatch [Final report]

The adoption of pond aquaculture depends in part on its expected net returns. This investigation aimed to provide research and extension workers with a user-friendly rapid evaluation tool with which to assess the potential economic risks of a given technology. In the second year of this study, researchers tested the rapid decision economic tool by testing two case studies; using the tool, the economic risks were evaluated for an independent, small-scale tilapia producer in Honduras and for three production practices for small-scale production, also in Honduras. With the @Risk add-in to the Excel, program, the user can enter data on the minimum, most-likely, and maximum values to determine their percentage of risk. The current version of the tool provides an easy and flexible way to evaluate the risks of small-scale tilapia production systems.

Research Area: Social and Economic Aspects
Research Theme: Adoption/Diffusion Research

9ADR3/Aquaculture training for Kenyan fisheries officers and university students/Bowman [Progress report]

A major reason for the low output of fish ponds in Kenya is a lack of technical training on all levels of production. This activity sought to produce a number of trainers with extensive practical fish production experience. In the current reporting period the Kenya Project continued scholarship support for two M.S. students, one at Moi University in Eldoret, Kenya, and one at Auburn University in Alabama. Also, the series of short courses for personnel of the Kenyan Fisheries Department (FD) was concluded during this reporting period; more than 80 FD staff received two weeks of training in pond construction and pond management techniques. An additional 26 people received three weeks of advanced training in pond construction, pond management, and business planning. Additional field days for about 50 farmers are planned for later in 2001.

Research Area: Social and Economic Aspects
Research Theme: Adoption/Diffusion Research

9ADR4/Establishment of companion sites in the Africa region/Bowman [Final report]

Research at an African site has been a major component of the PD/A CRSP since its beginning in 1982, and has mostly centered around the Rwasave Fish Culture Station in Rwanda and the Sagana Fish Farm in Kenya. During this reporting period the Kenya Project proposed to establish at least one companion site in the Africa region and to design and implement investigations at that site in accordance with the goals of the CRSP and the companion site. The sites selected were the ICLARM-Malawi National Aquaculture Center in Zomba, Malawi, and Bunda College near Lilongwe, Malawi. The results of the investigations conducted during this time are detailed in the reports 9ADR4A and 9ADR4B.

Research Area: Social and Economic Aspects
Research Theme: Adoption/Diffusion Research

9ADR4A/Effect of stocking size and nutrient inputs on productivity of Oreochromis shiranus in ponds/Bowman [Final report]

Malawian small-scale farmers widely practice extensive tilapia culture using the indigenous Oreochromis shiranus; however, stocking sizes and inputs vary greatly in these systems due to the lack of information available on the optimal fingerling size for increased efficiency of fish production. During the production cycle, stock manipulation is complicated and may be difficult to implement on small-scale farms. This study was designed to evaluate the production and profitability of tilapia in experimental ponds using three different fingerlings stocking sizes and two isonitrogenous pond input regimes and to recommend a fingerling stocking size and input regime that will result in improved production and profitability. During this study, inputs were applied to ponds stocked with fish at three stocking sizes so that each input regime supplied
20 kg N ha-1 wk-1, and fish were stocked at a rate of
2 fish m-2. Results showed that there were no significant differences in water quality between treatments, and all water quality parameters except water temperature were within acceptable limits. Results also showed that stocking fish at 5 g resulted in higher fish production and gross margin compared to stocking larger fish. Under certain conditions where inorganic fertilization is used, substituting napier grass for maize bran increases profitability without affecting overall fish yield. This study will provide extension workers with stocking strategies to profitably grow tilapia in fertilized ponds in Malawi.

Research Area: Social and Economic Aspects
Research Theme: Adoption/Diffusion Research

9ADR4B/Studies on potential use of salinity to increase growth of tilapia in aquaculture in Malawi/Bowman [Final report]

In agriculture, soils may be too saline to support profitable crop husbandry; such soils may be used alternatively for productive aquaculture if a salinity-tolerant fish species is used. In landlocked Malawi, there is only freshwater aquaculture at small-scale and semi-commercial levels with little knowledge about the environmental requirements of and best management practices for many of the currently cultured species. A classification of cultured tilapias based on differences in their metabolic rates in seawater and fresh water in Malawi was totally unknown before this study, which was conducted to determine which tilapia species could be best cultured in Malawi. Five taxonomic groups of tilapia were observed in waters of three salinity levels (0, 10, and 20). Tilapia rendalli and Oreochromis shiranus shiranus demonstrated the best growth in fresh water, so the range of these species would be effectively limited by salinity in the natural waters of Malawi and surrounding southern African countries. Also, this study found that O.shiranus chilwae (both Bunda College and Lake Chilwa stains) and O. karongae are potential candidates for brackishwater aquaculture in Malawi. These findings suggest that Malawi's marginal lands could contribute significantly to increased food production, improved human health, improved income generation, and increased total national fish production from aquaculture.

Research Area: Social and Economic Aspects
Research Theme: Adoption/Diffusion Research

9ADR5/Regional outreach in Africa/Bowman [Final report]

An important goal of CRSP adoption/diffusion research is to provide guidance to extension workers in order to further increase acceptance of CRSP technologies in host countries. One of the challenges of developing aquaculture in Africa is disseminating the information developed as a result of CRSP research. The goal of this activity was to promote contact and communication among aquaculture researchers and extension agents through participation in and organization of regional meetings. The current reporting period's activity allowed researchers from the Kenya Project to attend and present at the World Aquaculture Society and PD/A CRSP annual meetings. These meetings provided opportunities for CRSP researchers to share their findings, learn from others' experiences, and establish linkages with other aquaculture researchers.

Research Area: Social and Economic Aspects
Research Theme: Adoption/Diffusion Research

9ADR6B/Production of improved extension materials/Brown [Final report]

One goal of adoption/diffusion research is to assist extension workers to increase the adoption of CRSP-developed technologies in host countries. A number of methods developed as a result of CRSP research are available to farmers to minimize the cost of feeding tilapia grown in ponds in the Philippines. Currently this information is being spread by word of mouth, workshops, and newsletters. Through this activity extension materials were created and disseminated among tilapia farmers in the Central Luzon region of the Philippines. Extension brochures included information realized from over two years of CRSP Ninth Work Plan Philippines Project research on reducing costs in the initial phase of grow-out, the use of subsatiation feeding levels, and the cost benefit of using only light application of fertilizers. Since farmers in the Central Luzon region are generally receptive to the adoption of new technologies, it appears likely that a significant portion of the hundreds of farmers reached will implement what they learned from the brochures on their own farms.

Research Area: Social and Economic Aspects
Research Theme: Adoption/Diffusion Research

9ADR7/Decision support for policy development: Planning conferences for collaborating researchers, public agencies, and nongovernmental organizations working in aquaculture/Verma [Final report]

The Honduras Project focuses on strengthening local capabilities to extend findings of CRSP research. The initial meetings showed that a large network of nongovernmental organizations (NGOs) in Honduras operates at the village level; improving the linkages among these NGOs could increase the effectiveness of their work. The objective of this activity was to create an environment for developing linkages in order to reach out to NGOs, extension agents, and farmers via a website, focus groups, training meetings, and printed documents. The Red de Desarrollo Sostenible-Honduras (RDS-HN) is a local network established to provide information about forest and natural resource systems. RDS-HN, in collaboration with Honduras Project investigators, was engaged in developing a Web-based Information Delivery System for Tilapia (WIDeST). WIDeST provides information on tilapia production and related topics, natural resources of Honduras, contact information for NGOs, chat-room facilities, and an email facility that allows users to ask questions and get answers from an expert. From its inception in March 2001 the website, <www.acuacultura-ca.org.hn>, had more than 6,800 visitors in just five months.

Research Area: Social and Economic Aspects
Research Theme: Adoption/Diffusion Research

9ADR8/Production strategies characterizing small- and medium-scale tilapia farms/Verma [Final report; report title different than investigation title in Addendum to the Ninth Work Plan]

This study examined Honduran farmers who do not currently grow tilapia and compared them to farmers in their region who have adopted tilapia farming. To obtain information, 128 farmers were selected at random and interviews were conducted. This sample constituted a representative portion of the population of small-scale farmers in Honduras. The analysis profiled basic differences between the two categories of farms, their operators, and their households in areas such as age, gender, marital status, and income. Results showed that younger farmers were more likely to become involved with tilapia farming, married farmers were more likely to grow tilapia, and those who grow tilapia reported having higher average incomes than non-tilapia growers. The results of this study will provide additional guidance to the technology development and outreach efforts of the PD/A CRSP in Honduras.

Research Area: Social and Economic Aspects
Research Theme: Adoption/Diffusion Research

9ADR9 and 10/Technical assistance for fingerling production serving small- and medium-scale tilapia producers & Training and technical assistance for Honduras institutions working with small- and medium-scale tilapia producers/Verma [Final report]

Two critical issues facing smaller-scale tilapia farmers in Honduras are an inconsistent and often insufficient supply of fingerlings, especially for those in remote areas, and the lack of availability of technical assistance. Farmers find that transport of the fingerlings is difficult, costly, and hard to organize. A number of nongovernmental organizations (NGOs) have been active in rural development, but the amount of technical information available is insufficient for productive pond management. The first objective of this activity was to provide information required to develop and strengthen small- and medium-scale producers of tilapia fingerlings. The second objective was to identify the NGOs and agencies interested in incorporating small-scale fish farming into their development programs and then provide technical assistance and training to their field staff. During this reporting period a two-day technical workshop was held for actual and prospective fingerling producers, and more than 30 publications on fingerling production and pond management practices were incorporated into a web-based information system developed in cooperation with a local NGO. Also, 20 NGOs expressed their willingness to incorporate aquacultural development into their programs.

Research Area: Social and Economic Aspects
Research Theme: Adoption/Diffusion Research

9ADR11/A manual of fertilization and supplemental feeding strategies for small-scale Nile tilapia culture in ponds/Diana [Final report]

The PD/A CRSP has been working to improve aquaculture in Thailand continuously since 1982. This activity was conducted to summarize the PD/A CRSP work on Nile tilapia pond culture in Thailand. A manual was developed aiming to provide simple guidelines of fertilization, supplemental feeding, and pond management for small-scale Nile tilapia pond culture and to provide simple extension and training materials to extension workers, trainers, and well-educated farmers. Small-scale fish farmers in Asian countries should benefit from the use of this manual through effective use of organic and inorganic fertilizers and feeds to increase fish production, achieve higher economic returns, and reduce environmental impacts.

Research Area: Social and Economic Aspects
Research Theme: Regionalization Activities

9RA1/Establishment of new collaboration in Bangladesh/Diana [Final report]

The PD/A CRSP has not yet expanded to Southern Asia, where a large part of the population might benefit from improved aquaculture, especially in countries like Bangladesh. Fisheries and aquaculture are particularly important to Bangladesh's economy in terms of nutrition, income, and employment, but population growth is rapidly degrading natural habitat and drastically reducing the availability of fish to Bangladesh's people. Indian major carps have been the dominant cultured species, but tilapia is now playing an increasing role in solving problems of malnutrition and alleviating poverty in Bangladesh. Activities were conducted by researchers at the Asian Institute of Technology in order to establish a new link to a Bangladesh institution and to identify a potential PD/A CRSP site in Bangladesh. Contact was made with Bangladesh Agricultural University (BAU), the sole trainer of fisheries and aquaculture graduates in Bangladesh, where interest was expressed in the potential development of collaborative research activities between the PD/A CRSP and BAU. Several nongovernmental organizations also expressed interest in collaborating to maximize fish production, maintain good water quality, reduce environmental degradation, and maximize economic returns in Bangladesh.

Research Area: Social and Economic Aspects
Research Theme: Decision Support Systems Research

9DSSR2/Decision support systems for fish population management and scheduling in commercial pond aquaculture operations/Bolte [Progress report]

Commercial large-scale aquaculture producers commonly stock multiple fish lots at a time in order to continually supply fish to markets or processors. The distribution of fish sizes over time can be modeled mathematically in order to estimate growth and harvest parameters. This study focused on developing software tools that could analyze the fish population size distributions in commercial catfish opera
tions in the southeastern US and also be adaptable to other types of operations and locations. During this reporting period, progress was made in two primary areas: continued development of models of size distributions and their dynamics through time related to biological and management factors; and software development for the decision tool deliverable from this study.

Research Area: Social and Economic Aspects
Research Theme: Decision Support Systems Research

9DSSR3/Enhancing the POND decision support system for economics, education, and extension/Bolte [Progress report]

This investigation enhances and refines the POND software to better manage commercial production facilities, primarily by applying the core models of facility processes to applied management. Efforts include creating tutorials for easier use in educational and extension environments, updating the user's manual, and incorporating a shrimp growth and development model into POND. With these additions, POND has become a powerful decision support tool of the PD/A CRSP available to end users worldwide via the Internet.


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