PD/A CRSP Eighteenth Annual Administrative Report
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Research conducted under the Eighth and Ninth Work Plans includes nine of the fifteen themes outlined in the Continuation Plan 19962001 (see also Tables 1 through 4 on pp. 58 of the present report). In the reporting period (1 August 1999 through 31 July 2000), CRSP scientists conducted research in the following areas: pond dynamics, feeds and fertilizers, reproduction control, new aquaculture systems/new species, effluents and pollution, appropriate technology, marketing and economic analysis, adoption/diffusion, and decision support systems.
A summary of each study report received during the reporting period is presented below. Reports are identified by research area, research theme and code, project leader, and report title. In addition, information about the status (i.e., final vs. progress) of each report is also provided. For example, a final report was owed if the completion date for a study fell within the reporting period; similarly, if a study was not scheduled to be completed until after the close of the reporting period, a progress report was owed on 31 July. Please see Appendix 5 for a tabular overview of reports received, themes addressed, and study completion dates (where these differ from completion dates listed in the Eighth or Ninth Work Plan, it is owing to schedule changes requested and approved in the reporting period).
9PDR2/Pond soil characteristics and dynamics of soil organic matter and nutrients/Boyd [Progress report]
Historically, little work has been conducted on the role of bottom soils in pond aquaculture. As levels of production have increased, it has become apparent that bottom soils are an important factor in pond dynamics. This study is a continuation of Eighth Work Plan studies to characterize pond soils. Three ponds from a freshwater site at the Ayutthaya Fisheries Station and three ponds from a brackishwater shrimp farm at Banggachi, Thailand, were cored in September 1999. Moisture content, pH, organic carbon, nitrogen, and phosphorus decreased with depth; sulfur also increased with depth. Calcium, magnesium, potassium, and sodium were unexpectedly high at the freshwater site. Concentrations of minerals and nutrients were greater at the brackishwater site than at the freshwater site; this was due to intensive farming practices involving high inputs of nutrients and organic matter and to the naturally occurring concentrations of minerals in salt water at the brackishwater site. Young and old ponds developed profiles with distinct horizons. Horizon development is highly influenced by external input of soils, followed by internal input of organic matter, internal resuspension and resedimentation, and changes in soil properties resulting from nutrient and lime inputs. This study suggests that the simplest and most reliable method of pH measurement, direct insertion of a standard pH probe into a 1:1 mixture of dry soil (dried at 40°C and pulverized to pass through a 2.36-mm screen) and distilled water, should be adopted as a standard procedure. Cores were selected from the CRSP site in the Philippines and from an additional site in Brazil and will be analyzed in the following months. Results from all sampled CRSP sites will then be used to develop a concept of pond soil development and a system of pond classification.
8FFR1K/Global Experiment: Optimization of nitrogen fertilization rate in freshwater tilapia production ponds/Bowman [Final report]
Prior PD/A CRSP research has addressed primary production in tilapia ponds through the addition of inorganic and organic fertilizers. While increased fertilization generally increases primary productivity (and thus tilapia yield) in aquaculture ponds, experiments to determine optimal levels of inorganic fertilization rates are lacking. Researchers at all PD/A CRSP sites undertook the Eighth Work Plan Global Experiment to accomplish the following objectives: 1) determine the optimal rate of nitrogen fertilization (in the presence of adequate phosphorus and carbon) to obtain optimal primary productivity and yields of Nile tilapia in freshwater production ponds; 2) determine the most profitable nitrogen fertilization rate; and 3) develop a full-cost enterprise budget for the most profitable nitrogen fertilization rate identified. This study summarizes results from cool- and warm-season experiments conducted at the Sagana Fish Farm, Kenya. In the cool-season experiment, ponds were stocked with sex-reversed Nile tilapia, Oreochromis niloticus, averaging 16.9 g at a rate of 1,000 kg ha-1 and with Clarias gariepinus fingerlings at a rate of 37 kg ha-1. In the warm season experiment, all ponds were stocked with sex-reversed O. niloticus at 1000 kg ha-1 and with C. gariepinus juveniles at 125 kg ha-1. Treatments for this experiment consisted of nitrogen (diammonium phosphate and urea) applied at 0, 10, 20, and 30 kg ha-1 wk-1. Phosphorous was applied at a rate of 8 kg ha-1 wk-1 to the three treatments receiving quantifiable urea. In both season trials there was a significant quadratic relationship between gross fish yield and nitrogen input. However, increasing nitrogen input beyond 20 kg ha-1 wk-1 did not result in increased tilapia yields. A partial budget analysis indicated that calculated rates of 19.9 and 16.0 kg N ha-1 wk-1 yielded the highest marginal returns for the cool- and warm-season experiments, respectively. These results are in the range of those reported from other CRSP sites. Clarias did not affect tilapia production and was not negatively impacted by high nitrogen levels. The results of this study, advocating a low-intensity approach to aquaculture, may be readily accepted by local farmers who are willing to adopt low-cost aquaculture methods over increasingly intensified approaches that drive up production costs.
8FFR1Ph/Global Experiment: Optimization of nitrogen fertilization rate in freshwater tilapia production ponds (Cool season trial)/Brown [Final report]
Prior PD/A CRSP research has addressed primary production in tilapia ponds through the addition of inorganic and organic fertilizers. While increased fertilization generally increases primary productivity (and thus tilapia yield) in aquaculture ponds, experiments to determine optimal levels of inorganic fertilization rates are lacking. Researchers at all PD/A CRSP sites undertook the Eighth Work Plan Global Experiment to accomplish the following objectives: 1) determine the optimal rate of nitrogen fertilization (in the presence of adequate phosphorus and carbon) to obtain optimal primary productivity and yields of Nile tilapia in freshwater production ponds; 2) determine the most profitable nitrogen fertilization rate; and 3) develop a full-cost enterprise budget for the most profitable nitrogen fertilization rate identified. This study summarizes results from a cool-season experiment conducted at the Freshwater Aquaculture Center of Central Luzon State University, Philippines. Ponds were stocked with sex-reversed male Oreochromis niloticus at an initial density of 1,000 kg ha-1. Treatments for this experiment consisted of nitrogen (urea and ammonium phosphate) applied at 0, 10, 20, and 30 kg ha-1 wk-1. Phosphorous was applied at a rate of 8 kg ha-1 wk-1 to the three treatments receiving quantifiable urea. Extrapolated gross fish yield was highest in the treatment receiving 30 kg N ha-1 wk-1 (2,671 kg ha-1), followed by the treatments receiving 10, 20, and 0 kg N ha-1 wk-1, in that order. These results are in the range of those reported from other sites. However, the variation in return was not statistically significant, indicating that while some fertilization is better than no fertilization for increasing yield, doubling or tripling the amount of fertilizer does little to increase yield. A partial budget analysis indicated that the 10 kg N ha-1 wk-1 treatment gave slightly higher profit than the treatments with higher fertilization. A net return of US$57 can be obtained from the culture of Nile tilapia in a 0.05-ha pond for 90 days. The results of this study, advocating a low-intensity approach to aquaculture, may be readily accepted by local farmers who are willing to adopt low-cost aquaculture methods over increasingly intensified approaches that drive up production costs.
9FFR2/Fish yields and economic benefits of tilapia/Clarias polyculture in fertilized ponds receiving commercial feeds or pelleted agricultural by-products/Bowman [Progress report]
High-quality, nutritionally complete supplemental feeds produce high fish yields; however, in many developing countries such feeds are limited. In Kenya, high-quality feeds are expensive, and poultry and bran diets are often substituted. However, poultry rations contain more energy per unit of protein than recommended, and brans are nutritionally deficient. This experiment examines appropriate feed/fertilizer combinations for tilapia that will increase natural food organisms in ponds, thus improving production. Three low-cost supplemental feeds were tested: rice bran, a commercially available pig finisher pellet, and a formulated, test-diet pellet. Fertilization regimes were the same for all three diets, consisting of application of diammonium phosphate and urea. Measurements of fish size, fish growth, and water quality parameters were taken throughout the experiment. Preliminary results indicate that average fish yield is greatest in ponds receiving pig finisher pellets, followed by the formulated, test-diet pellets, and finally by rice bran. Economic analyses also indicate that pig finisher pellets yield the greatest profit given the investment. Further analyses of collected data are currently being conducted.
9FFR2A/Stable carbon and nitrogen isotope analysis of tilapia and Clarias fed commercial feeds or agricultural by-products /Lochmann [Abstract; report title different than experiment title in Ninth Work Plan]
High-quality, nutritionally complete feeds produce high fish yields; however, in many developing countries such feeds are limited. In Kenya, high-quality feeds are expensive, and poultry and bran diets are often substituted. Feeds that consist of small particles are often unconsumed, and pelleting appears to increase efficiency of use. This experiment examines a variety of diets with the goal of developing a feed/fertilizer combination that is appropriate for fish farming in Kenya. Tilapia were cultured at the Sagana Fish Farm using three treatments: 1) a rice bran diet, 2) a pelleted poultry feed, and 3) a high-quality, nutritionally formulated pelleted feed. All treatments received identical chemical fertilization. Measurements of fish growth rate, fish yield, water quality, and reproduction were taken. Samples of feeds, fertilizers, fish, mud, and plankton are currently being prepared for isotopic analysis.
9FFR4/Timing of the onset of supplemental feeding of Nile tilapia (Oreochromis niloticus) in ponds/Brown [Final report]
Tilapia producers in the Philippines commonly provide supplemental feeds to fertilized ponds. Supplemental feeding, in addition to fertilization, is often done during the first 40 days of the grow-out period. CRSP research in Thailand, however, has shown that a delay in feeding onset of 80 days, rather than 38 days, after stocking results in no loss of productivity. On-farm trials to test the application of these results were conducted in Nueva Ecija, Philippines. Seven farmers each raised fish in two ponds: one with a 45-day delay in feeding and one with a 75-day delay. Ponds were stocked with Nile tilapia of the GIFT strain and fertilized with urea and ammonium phosphate at a rate of 28 kg N ha-1 wk-1 and 5.6 kg P ha-1 wk-1. Fish were given feeds consisting of 67% rice bran and 33% fish meal. There were no significant differences in final mean weight, daily weight gain, fish yield, or survival rate between the two treatments. A significant difference was found in the amount of feed used and its associated costs. A simple cost/benefit analysis showed that by delaying the onset of feeding, the net value of the crop was improved.
8RCR1C/Methods for the contribution from the male and female genome to sex inheritance/Phelps [Final report]
Sex inheritance in Nile tilapia does not conform to a 1:1 ratio of females to males, as expected from a simple Mendelian XX:XY sex determination process. All-male populations are desirable, but the widely noted variation and general unpredictability of tilapia sex ratios makes the selection of true-breeding YY fish difficult. This study is part of a three-phase Eighth Work Plan research program to characterize sex determination. Specifically, this study examined the role of autosomes. The experimental design used three strains of highly inbred tilapia from the Ivory Coast, Egypt, and Ghana. The design also used three variations in breeding: 1) single males with multiple partners, 2) single females with multiple partners, and 3) repeat spawns of the same pair. Results from all designs yielded mean average male populations of greater than 50%, with considerable ranges. For the entire population, the mean percent male was 54.1% with a range of sex ratios from single spawns of 16 to 100% male; this is a statistically significant variation from the expected 1:1 inheritance pattern. Results of this study did not clearly indicate that sex determination in tilapia is sex linked. Sex determination appears to be a product of individual parent contribution, making a true-breeding YY program difficult.
9RCR5B/Masculinization of tilapia by immersion in trenbolone acetate: Growth performance of trenbolone acetateimmersed tilapia/Fitzpatrick [Final report]
All-male populations of tilapia are desirable to prevent unwanted reproduction and because males grow more quickly than females. Past research has identified a diet with 17-methyltestosterone (MT)-treated food as an effective masculinizing agent. This experiment, one component of a three-part Ninth Work Plan examination of trenbolone acetate (TA), examines short-term immersion in TA as an alternative to treated food. TA has been used previously in the cattle industry and is considered a more potent masculinizing agent than MT. The effects of TA immersion were compared to the effects of MT treatment; these were both compared to results from a feeding control and an immersion control. Results showed that TA immersion led to significant masculinization of tilapia fry, but with a lower efficiency than the MT treatment. Neither treatment led to increases in fish growth; however, immersion in TA may remove some of the environmental risks of treatment with MT, which has been found to remain in pond sediments.
9RCR5C/Masculinization of tilapia by immersion in trenbolone acetate: Detection of trenbolone acetate after treatment/Fitzpatrick [Progress report]
Previous studies have shown that immersion in trenbolone acetate (TA) can be an alternative to the use of 17-methyltestosterone (MT)-treated food to achieve all-male tilapia populations. However, the concentration of TA in solution is greater than that of MT in treated food, and the costs of immersion are greater than that of food treatment. This study examines the fate of TA in solution and the potential for reuse of immersion water. Tilapia fry were immersed in water containing either TA or an ethanol control. An additional control consisted of hormone-treated water that did not receive fry. Before, during, and after immersion and fry removal, water samples were tested to detect remaining levels of TA. Initial results have shown that TA concentrations are highly variable, with some treatments showing an increase in TA after introduction and removal of fish. In addition, these results show that masculinization rates were low and mortality was high in TA-immersed fry. Thus, initial findings indicate that a target dose for TA immersion is difficult to achieve, perhaps due to TA precipitation in water. Additional trials are being conducted, both to validate existing results and to remove confounding variables.
9RCR6A/Monosex tilapia production through androgenesis: Selection of individuals for sex inheritance characteristics for use in monosex production/Phelps [Abstract; report title different than study title in Ninth Work Plan]
Sex inheritance in Nile tilapia does not conform to a 1:1 ratio of females to males, as expected from a simple Mendelian XX:XY sex determination process. All-male populations are desirable, but the wide variation and unpredictability of tilapia sex ratios makes the selection of true-breeding YY fish difficult. This study uses cross-breeding among and within nine families to determine a true-breeding tilapia strain. A total of 80 within-family and 65 cross-family spawns have been obtained from the nine families, with the goal of determining the heritability of sex and factors influencing it. In addition, the study is culturing progeny in aquaria at either 28°C or 36°C during the period of gonadal differentiation to determine the effect of temperature on sex ratios. Sex ratios will be determined and analyzed for frequency within families.
9RCR7/Monosex tilapia production through androgenesis/Shelton [Abstract]
Sex inheritance in Nile tilapia does not conform to a 1:1 ratio of females to males, as expected from a simple Mendelian XX:XY sex determination process. All-male populations are desirable to prevent unwanted reproduction and because males grow more quickly than females. Goals of this experiment are to produce a protocol for the production of androgenotes carrying only the paternal genome and to examine the mechanism of sex determination. In order to test for the succession of the paternal genome, a phenotypic marker must be developed. This experiment is currently examining color mutation as a phenotypic marker by crossing red tilapia with Ghana tilapia. Once the phenotypic marker is established, construction of the protocol will commence.
9RCR8/The application of ultrasound to produce all-male tilapia using immersion protocol/Diana [Abstract]
Masculinization of tilapia continues to be an important tool for aquaculturists to prevent unwanted reproduction and because males grow more quickly than females. Past and concurrent research has identified the hormones 17-methyltestosterone (MT) and andostrenedione as effective masculinizing agents. One of the objectives of this investigation is to examine the efficacy of using ultrasound technology to enhance the delivery of hormones using immersion protocol. MT and andostrenedione were tested during one- or two-hour treatments with concentrations of 100 and 500 µg l-1. Fish were treated on days 10 and 13 post-fertilization. In this test, the use of ultrasound showed a significantly higher rate of masculinization than that seen in a control. Further tests will examine two more potent hormones using the same immersion protocol.
9NS1/Lotus-fish culture in ponds: Recycling of pond mud nutrients/Diana [Abstract; report title different than experiment title in Ninth Work Plan]
Nutrient enrichment of pond waters is an essential management practice in aquaculture, particularly in semi-intensive and intensive culture systems. Nutrients, and in particular phosphorus, accumulate in pond muds, which serve as a sink. Pond muds have been used to fertilize land crops, whereby phosphorus is extracted and used. However, removing pond mud is labor intensive. This experiment examines whether the alternative practice of lotus-fish culture can utilize these reserved nutrients. Ponds will be cultivated with fish alone, lotus alone, and fish and lotus together. Fish were stocked at 2 fish m-2 and lotus plants were stocked at 20 plants per 200-m2 pond. Treatment ponds stocked with tilapia were fertilized weekly with urea and triple superphosphate (TSP) at rates of 28 kg N and 7 kg P ha-1 wk-1; no fertilizer was applied in ponds with lotus alone. After fish harvest, nutrient recovery rates, fish growth rates, and mud characteristics will be analyzed. Cost analyses will also be performed.
9NS2/Culture of mixed-sex Nile tilapia with predatory snakehead/Diana [Abstract]
Intensive culture of Nile tilapia can reap profits. However, intensive culture can also lead to overpopulation of tilapia ponds, which leads to a loss of efficiency, as growth is stunted by a shortage of food. Predators such as snakehead (Channa striata) have been reported as effective in reducing population numbers, but the most effective densities of snakehead are unknown. This experiment examined the efficiency of snakehead in controlling tilapia reproduction and its effect on tilapia growth and production. Six treatments were monoculture of sex-revered tilapia, monoculture of mixed-sex tilapia, and polyculture of mixed-sex tilapia with snakehead at stocking ratios of 10:1, 20:1, 30:1, 40:1, and 80:1. Initial results from trials in 1999 showed that snakehead can control overpopulation of mixed-sex Nile tilapia. However, the snakehead burrowed through pond walls and moved freely among ponds, confounding results and necessitating duplication of the experiment.
9NS3/Development of sustainable pond aquaculture practices for Colossoma macropomum in the Peruvian Amazon/Kohler [Progress report; report title different than investigation title in Ninth Work Plan]
Evaluating the aquaculture potential of local and native species remains a need in Peru, as few production technologies for species in the Amazon basin have been developed. In addition, the nutrition requirements and optimal stocking densities of local species such as Colossoma spp. and Piaractus spp. are poorly understood. This investigation addresses these topics for Colossoma macropomum. C. macropomum was cultured at densities of 2,500, 3,250, and 4,000 fish ha-1 and fed a locally prepared diet. The mean weight decreased with increasing density, but feed conversion efficiency increased proportionately with increasing density. There was no significant change in survival. The study also examined financial aspects of Colossoma culture and found it to be economically feasible.
9NS3A/Practical diet development for broodstock of Colossoma macropomum and Piaractus brachypomus/Lochmann [Progress report; report title different than study title in Ninth Work Plan]
Colossomid broodstock cultures in Peru suffer from inconsistent spawning. Inadequate nutrition of the brood stock may contribute to the spawning problem; however, little is known about broodstock nutrition. This investigation examines broodstock feedstuffs and diets with the goal of formulating diet and spawning procedures that will maximize broodstock spawning. Feed nutrients were analyzed using standard techniques. Results show that current Colossomid diets have an energy:protein ratio of 8.7, which is lower than the reported range of efficient values and indicate that the diets are neither cost-effective nor efficient, as broodstock may metabolize protein for the purposes of growth and at the expense of reproduction. Lipids are naturally in the diet; however, there are not enough data to determine if the amount in the diet is sufficient for reproduction. Results also show that vitamin C must be added in a stable form. This investigation also examined vitamin E, carotenoids, and amino acids. Trials are being conducted to ascertain specific vitamin C and E requirements.
9NS4/Semi-intensive culture of tilapia in brackishwater ponds/Diana [Abstract]
Many tilapia species, including Thai red tilapia, can grow successfully in euryhaline water after proper acclimation. However, information on semi-intensive tilapia culture in saline ponds is almost nonexistent. The objectives of this experiment are to 1) determine appropriate fertilization regimes, 2) investigate nutritional value and digestibility of specific marine phytoplankton, and 3) determine the utility of underutilized or abandoned shrimp ponds for tilapia production. This experiment is examining the impacts of two fertilization regimes (28 kg N and 7 kg P ha-1 wk-1 and 28 kg N and 14 kg P ha-1 wk-1) and three levels of salinity (10, 20, and 30). This experiment will also examine budgets of brackishwater ponds to estimate the cost of inputs versus the value of the fish crop.
9ER1/Use of pond effluent for irrigation in an integrated crop/aquaculture system/Wood [Final report]
Aquaculture in Kenya is practiced in water retention reservoirs and fish ponds. In addition, 80% of Kenya's land falls in arid and semi-arid zones, where rains are unpredictable. Effluents from aquaculture operations can be used as irrigation waters, thereby aiding farmers' needs; however, the interaction between effluent nutrients, applied fertilizers, and crops is unknown. This investigation consisted of two experiments. The first experiment sought to determine the effects of pond effluent when used as irrigation water for fertilized and unfertilized crops of French beans and kale. To do so, a factorial design was constructed consisting of six treatments in the first growing season and twelve treatments in the second growing season, with varying rates and types of irrigation and fertilization. Fresh and dry matter yields were recorded at harvest, and samples were collected for determination of tissue nutrient content. After the second season, the highest yield for French beans was found in crops that had been irrigated with pond water and then fertilized. However, the highest yield for kale was found in crops that had been irrigated and fertilized using traditional sources. The second experiment examined the effectiveness of two types of soil (a black clay vertisol and a red clay cambisol) in removing nutrient effluents. Results from a laboratory experiment involving packed columns of soil showed that land soils can remove substantial amounts of phosphorus and nitrogen from pond effluents, potentially aiding in pollution reduction.
9ER2B/Fate of methyltestosterone in the pond environment: Detection of MT in pond soil from a CRSP site/Fitzpatrick [Final report]
This is the second phase of an investigation examining the fate of 17-methyltestosterone (MT) in the pond environment. The first phase found that in the laboratory, MT persists in the soil for up to eight weeks. Persistent MT may lead to unintended exposure of humans and animals. The second phase examined the persistence of MT in semi-closed pond systems at CRSP sites with previous MT use (Kenya) and with no history of MT use (Mexico). Soil samples were collected after administration of either an MT or a control diet to fry. Concentrations of MT in the water, soil, and water-soil interface were ascertained using radioimmunoassay techniques. Results showed that levels of MT at the Kenya site exhibited levels higher than laboratory background, perhaps due to a gradual accumulation of MT over its history of use. In Mexico, levels returned to near background levels on the last day of the experiment. Levels of MT in the water and gradually accumulating levels in soils may lead to unintended exposure of humans and fish and may cause intersex characteristics in exposed fish.
9ER2C/Fate of methyltestosterone in the pond environment: Impact of MT-contaminated soil on tilapia sex differentiation/Fitzpatrick [Final report]
This is the third phase of an investigation examining the fate of 17-methyltestosterone (MT) in the pond environment. The first two phases found that MT persists in soil for up to eight weeks after treatment termination, adding to concerns about unintentional MT exposure. This phase examined whether the persistence of MT in soils influenced sex differentiation of tilapia. In the experiment, one set of fry was fed MT-impregnated food. When the cycle of MT-treatment was over, the fry were then fed a control diet. Simultaneously, another set of fry were fed a control diet only. After treatment, sex ratios were determined. Rates of masculinization were lower in control groups. Fish fed MT-impregnated food and then fed a control diet while being maintained in the MT-treatment tanks showed no difference in sex ratio from fish that were fed a control diet throughout the experiment. However, several individuals in the MT-treatment tanks had intersex gonads, suggesting some impact on development.
9ER3/Integrated recycle system for catfish and tilapia culture/Diana [Final report]
Clarid catfish have been one of the most popular freshwater fish cultured in Southeast Asia. Catfish can be grown at extremely high density and are fed mainly trashfish, chicken offal, or pelleted feed, which cause poor water quality and phytoplankton blooms. Past studies have shown that tilapia can feed on phytoplankton from catfish culture systems, improving water quality and producing an extra crop. This experiment examined the relationship between catfish and tilapia culture and water quality through the use of three treatments: 1) catfish alone, 2) catfish and tilapia without artificial water circulation, and 3) catfish and tilapia with artificial circulation. Growth rate, water quality, and soil analyses were conducted throughout the experiment. Results showed no significant differences in catfish and tilapia growth rates and survival rates among all treatments; however, high mortality of tilapia was observed in the artificial recirculation treatment, perhaps due to heavy loading of wastes. Nutrient budgets showed that total nitrogen and total phosphorus contents in pond effluents in treatments with catfish-tilapia polyculture were significantly lower than those with catfish alone. The results of this experiment indicate that Nile tilapia can effectively recover nutrients contained in wastewater of intensive catfish culture. They further suggest that natural water circulation between catfish and tilapia compartments can cost-effectively reduce nutrient contents in pond effluents.
9ER4/Effects of water recirculation on water quality and bottom soil in aquaculture ponds/Boyd [Progress report]
Nutrient enrichment of pond waters is an essential management practice in aquaculture, particularly in semi-intensive and intensive culture systems. However, the discharge of pond effluents may result in deterioration of the receiving waters due to high organic carbon, nitrogen, and phosphorus concentrations. Growing concern about the release of nutrient-enriched effluents has created a need for more environmentally responsible techniques for managing pond waters. This study examined the effectiveness of a water-recirculating system in removing organic carbon and nutrients from pond waters and soils. Shrimp ponds were subjected to one of three treatments: 1) high-density stocking with water recirculation into another pond of equal volume without shrimp, 2) high-density stocking without water recirculation, and 3) low-density stocking without water recirculation. Recirculation of water had no effect on shrimp yields. Recirculation effectively reduced the amount of total ammonia nitrogen, but the concentrations of all other variables were either significantly greater or no different than the ponds without recirculation. Soil samples are currently being analyzed.
9ATR1/On-farm trials: Evaluation of alternative aquaculture technologies by local farmers in Kenya/Bowman [Progress report]
On-farm trials are valuable for two reasons: they offer an opportunity to test, in a real-world setting, the effectiveness of technologies developed in controlled laboratory settings, and they allow for communication of management alternatives to both farmers and extension agents associated with the trials. Farmers participating in these trials elected to practice either a "no cash expenditure" type of management, which relied on inputs such as manure found on their farm, or a "purchased feed/fertilizer" management scheme. Four treatments were applied, using monosex or mixed-sex tilapia in one of the two management schemes. Extension agents visit farmers regularly. Ponds have been stocked, and weekly or as-needed data on inputs, water addition, mortality, expenses, weight, and length are recorded. Fish harvests will take place in late 2000.
9ATR2/Linkage of aquaculture within watersheds and concurrent design of hillside ponds/Verma [Abstract]
The promotion of tilapia culture in Honduras can result in improved nutrition and economic status of local farmers. The majority of farmers who might benefit from the addition of aquaculture to their production systems own or farm land located on hillslopes (generally land with a slope of 2 to 15%). Poor management of hillslopes for agricultural use has resulted in deterioration of natural resources and environments. In addition, fish ponds are rare on hillsides due to engineering constraints. Hillside aquaculture operations must be sited carefully, taking into consideration environmental and stakeholder needs. This investigation examines the design of hillside ponds. Two types of ponds are being examined: watershed ponds in which water is supplied by rainfall and spring-fed ponds. Additional testing variables include pond size, hillside slope, ground cover, and soil. Design modules have been constructed for nine combinations of tested variables. The designs are intended not only to meet engineering requirements, but also to meet stakeholder concerns, such as investment constraints and land availability. Researchers will include spatial data analysis tools in their development of designs. Farmers will then be encouraged to adopt the designs for testing.
9MEAR3/Development of Central American markets for tilapia produced in the region: Potential markets for farm-raised tilapia in Honduras/Engle [Progress report; report title different than activity title in Ninth Work Plan]
Much of CRSP research focuses on increasing tilapia production yields. This activity builds on past research efforts by identifying potential markets for tilapia in Honduras. Currently, most Honduran-produced tilapia is exported. In 1999, a survey was distributed to restaurants and supermarkets along the major north-south route in Honduras. The survey examined seafood and tilapia sales, consumer reactions to tilapia, and tilapia supply. Additional survey questions examined store and restaurant sizes and histories, as well as clientele characteristics and preferences. Raw scores of this survey are presented in the report; analysis of scores will be conducted by late 2000.
9MEAR4/Economic and social returns to technology and investment in Thailand/Engle [Progress report]
This two-phase study was designed to develop and refine a model of economic tradeoffs associated with adopting CRSP-developed technologies. In the first phase, researchers assessed the choices a small-scale tilapia farmer in Thailand would make based on the availability of four CRSP-developed technologies: 1) low-intensity inorganic fertilization, 2) organic fertilization with collected chicken manure, 3) organic fertilization in layered pondchicken coop systems, and 4) high-input green water use. Existing secondary data were used to examine gross and net expenditures and revenues, supply availability and price, and financing amount and availability as they affect the choice of technology. A mixed-integer programming model used 11 scenarios to determine efficient choices. The study found that the layered systems provided the greatest returns but required heavy operating costs. Low-intensity inorganic fertilization required the least investment but always resulted in the lowest net returns. When loan amounts are restricted, the model indicated organic fertilization with collected chicken manure to be the optimal choice. High-input green water technology is optimal only when fingerling availability is restricted. The second phase of this study will involve primary data collection by survey to determine actual rates of adoption of CRSP-developed technologies and provide estimates of the social and economic returns generated by CRSP research in Thailand.
9MEAR5/Rapid economic evaluation tools/Hatch [Progress report]
Among the factors influencing the adoption of tilapia production technologies are the associated costs, risks, and incentives. This study involves development of a tool to quickly estimate the economic consequences of a given technology. Such a tool would enable researchers to consider economic as well as physical and biological considerations in designing research to develop effective and efficient tilapia production technologies. In the first year of this study, researchers tested a prototype of a rapid decision economic tool by evaluating two technologies developed under an earlier CRSP research project in Honduras: 1) chemical fertilization and 2) fertilization followed by supplemental feeding. The decision tool is being developed using the software programs Excel and @Risk. Use of SIMTool and integration with the CRSP-developed POND© simulation software are being considered. The first run of the prototype tool showed that the fertilization-followed-by-supplemental-feed technology provides a higher net income and a lower risk of losing money in the short run than the chemical-fertilization technology. This tool, when fully developed, should help aquaculture researchers judge economic incentives and risks of various technologies.
8ADR1-2/Sources of technical assistance for fish farmers in the Peruvian Amazon/Molnar [Final report; report title different than study title in Eighth Work Plan]
Adoption of PD/A CRSP technologies and research findings by local farmers can be facilitated with knowledge of local pond environments and cultural practices. In particular, attitudes toward extension agents providing technical assistance are particularly important, as it is through extension agents that CRSP-developed findings are translated and diffused to hatcheries, fish farmers, and other agencies and organizations involved in aquaculture development. This study examined prior experience with and attitudes toward extension agents in the Napo, Tamishiyacu, and Tahuayo river system areas north and south of Iquitos, Peru. A survey developed for use in other CRSP countries was modified and distributed to 146 fish farmers in those regions. The survey asked participants about species raised, land holding patterns, and their experience with and expectations of those providing technical assistance. Results of the survey show that attitudes toward extension did not vary greatly based on the species cultured; however, attitudes varied based on land holdings. Those holding more parcels of land reported less contact with extension than those holding more hectares of land. Nearly all farmers surveyed wanted extension contact in the future.
8ADR1-3/Identifying goals and priorities of fish farmers in the Peruvian Amazon/Molnar [Final report; report title different than study title in Eighth Work Plan]
Fisheries in the Amazon basin play a vital role in the economic and nutritive health of local populations. Interest in aquaculture has been growing, in large part due to support and training from government agencies, nongovernmental organizations, and missionaries. Aquaculture is also one way of combating the cyclical nature of Amazon fisheries, in which fishing is more difficult during high-water periods. This study surveyed 143 fish farmers in the region. Results show that the majority of farmers grow more than two species of fish, with tucanare and bujurqui being the most frequently grown combination. The fish most frequently grown in monoculture were boquichico and gamitana, local fish with abundant fingerlings in the rivers and simple diets. In general, respondents had favorable attitudes towards fish farming and found that it did not affect their ability to care for their families or other crops. The largest problem associated with fish farming was loss due to human and animal predation. The majority of respondents felt optimistic about aquaculture growth in the future.
9ADR3/Aquaculture training for Kenyan fisheries officers and university students/Bowman [Progress report]
Aquaculture productivity in Kenya is low, in part due to a lack of adequate technical skills among fisheries officers and university personnel involved with the field. The objectives of this activity are to increase the pond management skills of fisheries and extension personnel and to enhance the research and extension opportunities of Kenyan university students likely to seek employment in the aquaculture sector. To fulfill these objectives the CRSP project in Kenya has begun scholarship support for two graduate students and offers stipends for undergraduate and graduate level research at Sagana Fish Farm. In addition, the project has offered a series of four short courses, lasting two weeks each, which were attended by over 80 Kenya Fisheries Department personnel. Farmer field days, with an anticipated total attendance of 50 farmers, have been planned for late 2000.
9ADR4/Establishment of companion sites in the Africa region/Bowman [Progress report]
CRSP research in Africa has centered around the Rwasave Fish Culture Station in Rwanda (1983 to 1994) and the Sagana Fish Farm in Kenya (1997 to present). In the current period, the Kenya Project received funding to regionalize CRSP efforts and thus extend the validity and benefits of CRSP research. This activity commenced by identifying companion sites and beginning preliminary research investigations at those sites. Selected companion sites are the ICLARM-Malawi National Aquaculture Center in Zomba, Malawi, and Bunda College near Lilongwe, Malawi. Research at the National Aquaculture Center is currently underway to examine the effect of stocking size and nutrient inputs on productivity of Oreochromis shiranus. Work is being conducted by students from the National Aquaculture Center and Bunda College. Research on the use of salinity to increase growth of tilapia is scheduled to begin at Bunda College in the fall of 2000.
9ADR5/Regional outreach in Africa/Bowman [Progress report]
One of the challenges facing the development of aquaculture in Africa is the dissemination of research information to local users. Extension services are best suited to do this; however, currently there is a lack of adequate communication and cooperation between researchers and extension agents in Kenya and surrounding areas. The goal of this activity is to promote communication between aquaculture researchers and extension agents through participation in and organization of regional meetings. In this reporting period, researchers at Sagana Fish Farm orchestrated a workshop on pond aquaculture, attended and made presentations at conferences in the US and Africa, and established numerous linkages.
9ADR6A/Workshop on the timing of the onset of supplemental feeding of Nile tilapia (Oreochromis niloticus) in ponds/Brown [Final report; report title different than activity title in Ninth Work Plan]
Socioeconomic studies carried out by CRSP researchers have shown that farmers in Central Luzon, Philippines, are receptive to the adoption of new technologies. Feeds and Fertilizers Research performed with seven on-farm trials has shown that delayed feeding (75 days rather than the usual 45 days) does not reduce pond productivity but does reduce investment costs. The objective of this activity was to disseminate these results to other area farmers through a workshop at the Freshwater Aquaculture Center, Central Luzon State University (CLSU). Attendees of the workshop included the farmers of the previous trials, two additional farmers, and CLSU students, faculty, and administrators. Farmers who attended were impressed by the results and indicated that they would immediately adopt the practice. Other farmers in the region have also learned of the research through word-of-mouth and have adopted the delayed feeding practice. This workshop will be complemented by another activity (9ADR6B), the development and dissemination of printed materials.
9ADR6B/Production of improved extension materials/Brown [Abstract]
Socioeconomic studies carried out by CRSP researchers have shown that farmers in Central Luzon, Philippines, are receptive to the adoption of new technologies. Feeds and Fertilizers Research performed with seven on-farm trials has shown that delayed feeding (75 days rather than the usual 45days) does not reduce pond productivity, but does reduce investment costs. As farmers are receptive to this change in practice, extension materials will be created and distributed to complement a workshop that was held at Central Luzon State University (9ADR6A). Development of extension materials is underway; materials may include technical bulletins and fact sheets.
9ADR7/Decision support for policy development: Planning conferences for collaborating researchers, public agencies, and nongovernmental organizations working in aquaculture/Verma [Abstract]
The "Red Nacional de Acuicultura" (National Aquaculture Network) was created by the United Nations Food and Agriculture Organization (FAO) in 1992 with the purpose of integrating international institutions with the private and public sectors in Honduras. CRSP researchers at the Escuela Agrícola Panamericana El Zamorano (referred to as Zamorano) in Honduras are working to strengthen this network as a hub for information exchange, research activity, and policy leadership. Using Zamorano as a base, this activity will foster linkages among national and regional organizations and disseminate tilapia production information. Initial meetings have shown that communication among organizations and between organizations and farmers is lacking. To address this and other needs, a series of three meetings are being held for various stakeholders. One of the primary topics will be a Web-based Information Delivery System for Tilapia (WIDeST). WIDeST makes knowledge of tilapia production available to farmers, nongovernmental organizations, policy makers, businesses, and consumers. WIDeST is expected to aid in the process of information dissemination and institution linkage.
9ADR8/Production strategies characterizing small- and medium-scale tilapia farms: Approaches, barriers, and needs/Verma [Abstract]
Rural farmers in Honduras face numerous production and distribution challenges, making adoption of PD/A CRSP aquaculture technologies and research findings difficult. To understand these challenges and thereby facilitate use of aquaculture techniques, the current study is being undertaken. A survey instrument that has been used in research in other CRSP countries was modified and will be used to survey rural farmers. A 1996 evaluation of CRSP technologies in Honduras showed that rural farmers relied heavily on middlemen, sold their product largely to Honduran restaurants, and used word of mouth as a means of marketing. The current study will provide data on the changes since then in production practices and distribution strategies to verify and extend the previous research findings.
9ADR9/Technical assistance for fingerling production serving small- and medium-scale tilapia producers/Verma [Abstract]
An inconsistent and often insufficient supply of fingerlings is one of the central challenges facing Honduran tilapia aquaculture. The Comayagua research station does not produce a reliable supply, and private suppliers are more often geared toward large-scale commercial operations. Smaller-scale farmers must expend large amounts of energy locating and transporting fingerlings, when they are available. The objective of this activity is to address this constraint by providing technical assistance and training to current and potential fingerling suppliers to small- and medium-scale tilapia producers. Surveys have been conducted of farmers and restaurants to assess production and marketing needs of fingerling suppliers. A workshop will be provided for current and prospective fingerling producers.
9ADR10/Training and technical assistance for Honduras institutions working with small- and medium-scale tilapia producers/Verma [Abstract]
The Honduran national extension program in aquaculture is present in many regions, but it is fragmented and underfunded. In particular, activity with small- and medium-scale farms, which are mostly rural, has been largely ignored. Nongovernmental organizations (NGOs) are present in many of these rural regions but often lack the expertise to advise on issues related to tilapia aquaculture. This activity's objectives include identifying NGOs that are interested in incorporating aquaculture extension into their activities and then providing the technical assistance and training to allow them to do so. A meeting held in 1999 between collaborating institutions has identified potential NGOs, and training workshops are scheduled for Fall 2000.
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. The distribution of fish sizes through time can be modeled mathematically, allowing for estimation of growth and harvest parameters. As such, this study endeavored to modify existing POND© software and other models to develop new software that can be used to simulate population growth and fish biomass and to inventory fish stocks. A set of mass balance equations was used to describe fish size distribution as it relates to individual fish growth. The software provides two views: a facility-level view, showing a schematic of the entire farm, and a pond-level view, showing pond inventory, feed rate history, and a spreadsheet containing feeding, stocking, and harvest data. Using the summary data provided by these views, a user can quickly and easily view a pond's readiness for harvest. A final part of this study will be the development of training materials for a workshop on the use of the software.
9DSSR3/Enhancing the POND© decision support system for economics, education, and extension/Bolte [Progress report]
POND© software is a decision support tool developed by the PD/A CRSP for analyzing and projecting fish-culture and economic aspects of warmwater aquaculture production systems. This study is focused on enhancing the economic capability of the program by supporting partial budgeting and the inclusion of time-based costs. Efforts to create a task-oriented user interface have led to the formulation of "wizards," which automate key simulation tasks. In addition to enhancement of POND©, the researchers are releasing an additional decision support tool, AquaFarm©, which provides simulation of physical, chemical, and biological unit processes, facilities, and management systems for a broad class of aquaculture systems, including semi-intensive and intensive systems. AquaFarm© complements and expands many of the functionalities contained within POND©.
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