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Survey Study of and Stocking Densities for Tilapia-Shrimp Polycultures 10NSR3

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Survey Study of and Stocking Densities for Tilapia-Shrimp Polycultures

New Aquaculture Systems/New Species Research 3 (10NSR3)/Studies and Experiments/Various

Collaborating Institution
Asian Institute of Technology, Thailand
     Yang Yi

Central Luzon State University, Philippines
     Remedios Bolivar

Universidad Juárez Autónoma de Tabasco, Mexico
     Wilfrido Contreras-Sánchez

University of Arizona
     Kevin Fitzsimmons

Introduction
Shrimp ponds have been abandoned in many parts of the world due to diseases, poor management and environmental degradation. Tilapia production, supplemented with low densities of shrimp, in abandoned shrimp ponds may provide an opportunity to develop a sustainable aquaculture system that will support local inhabitants who have not benefited from the shrimp boom in many parts of the world. Polyculture or crop rotation of shrimp and tilapia may even be the modern equivalent of the Chinese polyculture of carp. Tilapia production in former shrimp ponds (with and without shrimp) has increased rapidly in many of the PD/A CRSP locations including Thailand, the Philippines, Honduras, Mexico, Peru and the inland desert of Arizona.

This would be a unique opportunity to take advantage of the strengths of the PD/A CRSPs locations and expertise to conduct cross-cutting research and make a contribution to groups who would be the most likely to understand and benefit from a sustainable production system. Farmers in several locations around the world appear to have demonstrated that tilapia and shrimp can in fact be grown together. There are several technical questions to be answered regarding optimal salinities, stocking densities, feeding rates, disease and parasite infestations, cost-benefits, and environmental impacts. These would be the first replicated trials and technical evaluation of the polyculture. This proposal brings together researchers and industry partners in several countries. The anticipated benefits of the research are: a production system that is more sustainable than the current shrimp farming system, opportunity for local inhabitants to have reliable job opportunities.

Shrimp aquaculture has been devastated in many countries due to a mix of disease outbreaks and decreasing yields. The progression of shrimp aquaculture has followed a familiar pattern throughout the tropics. Initially, farms are constructed in the most appropriate areas. These locations are characterized by good soils with proper pH, appropriate levels of clay, silt and sand, proper elevation, good access to clean water and convenient disposal of waste waters to a location which keeps wastes from being cycled back into the farm. These farms, if managed well, tend to be very profitable. This early success leads others to imitate the process as best they can. This has led to a "gold rush" attitude where excessive numbers of farms are built, often in ecologically fragile areas, especially mangrove forests. From a practical point mangrove forests, in general, are poor sites for shrimp farms. They do not have the proper soils, there is usually poor access to water, inadequate drainage due to low elevation and they are especially susceptible to storm damage.

A related phenomenon is overstocking of an existing farm. After the initial success of a farm, the managers often assume they can increase yields and profits by stocking more shrimp and feeding more heavily. This may work for one or two crops, encouraging even more stocking. But inevitably, the producer overshoots and a disease outbreak occurs because the animals have been overstocked and are stressed under the available environmental conditions in the pond.

In most cases, the farm managers react by increasing water flow through the farm or adding mechanical aeration. These do in fact address the problem but also increase operating expenses and environmental impacts. Added to this situation is the fact that the ponds must be properly maintained and the pond soils managed between crops. Many farms do not properly maintain their infrastructure or their pond environments. When multiple farms in one area reach this stage, there tends to be an environmental overload. The effluent from one farm becomes the supply water for another, the receiving environment cannot process the nutrient rich effluents, leading to eutrophication, and diseases are spread by water transfers, birds, and other vectors. Excessive pumping of water can lead to saltwater intrusion and depletion of freshwater aquifers. Farms that had been wildly profitable with little management, suddenly require more investment and sophisticated management for lower levels of profit. Some farms make the investment to operate in a more sophisticated and sustainable manner, many others just abandon the farm. In many countries the governmental oversight, environmental regulation and protection have been inadequate to avoid this serious ecological damage.

A related problem has been one of land tenure. In many instances investment groups have come in and gained control of coastal lands and hired local inhabitants. These people are usually happy to have the employment and appreciate the infrastructure (roads and electrification) which often accompany the farm. However, when these farms fail, the local inhabitants are often left with no jobs and environmental damages that impair their abilities to return to artisanal fishing or small-scale agriculture. Common environmental damages include salinization of soils, saltwater intrusion, loss of breeding areas for marine species, eutrophication, and changes in the water flow through estuaries.

One technique that has been tested to utilize abandoned shrimp ponds is to convert the pond to tilapia production. There have been several variations of tilapia production including rearing in seawater, brackish water and freshwater. Some have attempted polyculture with shrimp and some are using a crop rotation of tilapia and shrimp (Fitzsimmons, 2001).

Ecological Basis for Tilapia-Shrimp Polyculture
In nature, tilapia are omnivores. Young tilapia graze on algal and bacteria films scraping most hard surfaces with tongue and teeth. As they grow they also become effective filter feeders of phytoplankton and predators of zooplankton. Larger tilapia are less effective filter feeders but begin to graze heavily on macrophytic algae and aquatic plants. In extensive farming situations, tilapia filter feed on algae, prey of zooplankton and scrape films from any hard surfaces in the pond. In intensive farms, most nutrition is derived from pelleted feeds, although fish will continue to spend time scraping algal and bacterial films from all surfaces.

In nature, shrimp feed first on phytoplankton and then zooplankton during larval stages. As juveniles and adults they are omnivores and detritovores. Their natural behavior is to search the bottom substrates for decaying plant and animal material. They also constantly pick up sand grains and pieces of organic matter and graze off the algae and bacteria, drop the grain or particle and go onto the next item. In farmed settings shrimp feed on pellets and natural productivity in the pond. Research by Samocha et al. (1998), has demonstrated that shrimp can be reared in systems with little water exchange, taking advantage of the natural abilities of shrimp to thrive in conditions with high bacterial loading so long as dissolved oxygen levels and other water quality factors are maintained.

There are several variations on tilapia-shrimp polyculture: simultaneous, sequential, and crop rotation. In the simultaneous instance the fish and shrimp are grown together in a pond or raceway, in the sequential case the water is moved from one growing unit to another, and the crop rotation alternates tilapia and shrimp. There appear to be distinct advantages with each of these systems.

In a polyculture setting, tilapia and shrimp can utilize different niches in the culture setting. In an extensive farm, tilapia can filter feed on phytoplankton and zooplankton in the upper water column. Shrimp spend most of the time in the pond bottom grazing on bacterial films on the bottom substrate and on the detritus settling from above. This detrital matter consists of dying algae cells and fecal matter from the tilapia. In a more intensive farm receiving pelleted feeds, the tilapia monopolize the feed, especially if it is a floating feed. However, some feed particles always get to the bottom where the shrimp will get it. More importantly, the fecal matter from the tilapia contributes to the detrital rain that supports the shrimp. Macrobrachium-tilapia polyculture reduces the yield of prawns compared to monoculture, but increases total yield of fish and prawns (Garcia-Perez et al., 2000). A similar effect occurs with brackish water polyculture of tilapia and shrimp (Yap, 2001). Anggawa (1999) reported that yields of shrimp increased when tilapia were stocked into existing shrimp ponds. The suggested stocking rate was 20-25 g fish/m2 and the fish size at stocking of 50-100 g/fish. The use of all-male fish was needed to control reproduction. Fish were stocked when the shrimp biomass was at least 80 g/m2 (for 3-4 g shrimp) or 150 g/m2 (for 5-6 g shrimp). Tilapia harvest biomass was 40-50 g/ m2 and shrimp survival was 70%.

From the disease aspect, tilapia seem to provide advantages in several ways. Growers in Ecuador have reported that tilapia will consume dead or moribund shrimp in polycultured ponds. Cannibalism is one of the primary vectors for transmission of shrimp diseases. Tilapia, which do not appear to be susceptible or carriers of these viruses, disrupt cannibalism as a mode of transmission. Tilapia also consume small crustaceans in shrimp ponds. These crustaceans are of concern as potential vectors. Having tilapia directly in the ponds or alternating with shrimp in a crop rotation can be effective for reducing crustacean populations. Bacterial infections also may be impacted by polyculture. Vibrio and most other bacterial pathogens common in shrimp culture are gram negative while waters which have been used for fish culture tend to be predominated by gram positive bacteria. Using water from a fish culture pond seems to reduce the prevalence of luminous Vibrio bacterial infections in shrimp ponds (Yap, 2001). Growers in Asia and South America have provided anecdotal reports that shrimp production increases due to higher survival in some of these polyculture systems, however, carefully controlled and replicated trials are needed to better study these systems and confirm the results.

There may also be physical factors that improve shrimp survival and growth in polyculture and crop rotations. Tilapia disturb bottom sediments to a greater degree than shrimp, both in foraging and nest building activities. This may be beneficial in several ways. Disturbing the bottom could improve oxidation of the substrate and interrupt life cycles of shrimp pathogens and parasites. It could also release nutrients into the water column that could improve algae blooms. However, it is also possible that these activities may be detrimental. Disturbing bottom sediments could also negatively impact water quality, lowering dissolved oxygen levels, increasing turbidity from sediments and reducing algae blooms, ability to remove fish and shrimp, and most certainly increase the need to repair pond bottoms between crops. This particular aspect would require close attention and careful experimentation to gain a clear understanding.

Methods
The overall project is divided into 5 investigations: 3 survey studies of current tilapia-shrimp polycultures and 2 experiments testing aspects of the farming systems. The intention of the surveys is to examine how farmers in widely separated parts of the world are integrating tilapia-shrimp culture into a sustainable aquaculture system. As often happens, farmers are busy driving technological advances through necessity before the academic community can evaluate and document the most efficient techniques. The unique ability of the PD/A CRSP is our connection to aquaculture developments in Asia, Africa, and the Americas. By allowing aquaculture researchers to work with their domestic farmers and then sharing these findings, we should be able to discern which techniques are the most efficient, from environmental and economic aspects.

The five investigations are:

The overall project plan is to have several researchers conduct investigations in the form of survey studies at locations in their home countries and possibly a nearby country that is also practicing tilapia-shrimp culture. In several of these countries these investigations would be in conjunction with experiments that would be conducted to determine which conditions, especially stocking densities, are most appropriate in the host country.

Fitzsimmons, Yi, Bolivar, and Contreras, the project PIs, will coordinate the results of the survey studies to develop some international consensus on how these polyculture systems are working. In addition, each host country author will be encouraged to develop and publish his or her national results.

Thailand and Mexico will conduct a two-year experiment, rearing tilapia and shrimp in a polyculture setting. The intent of this experiment is to determine the proper stocking densities of shrimp and tilapia. In some countries the experiments will occur on campus where facilities are available. In other countries where facilities are not available, experiments will be conducted at a cooperating farm.

Details of Investigations A, C, and E

General Survey Methodology: The investigators will develop a contact list of farmers and community leaders in areas that have been impacted by shrimp pond abandonment. Face-to-face meetings will be arranged so that the researchers can visit the sites and document the degree of the problem with the abandoned farms. They will also use this time to contact and visit any farmers who have already tried tilapia-shrimp polyculture. Discussion of techniques, successes, and failures will be key. Finally, the researchers will develop lists of local contacts to share the research results. Especially important will be the social sector contacts who will need to share results with local inhabitants who may wish to utilize ponds which have been abandoned and are available to the local populace.

Survey: ­ The investigator will determine:

Investigators will customize the exact informational survey form in concert with one another to insure that the information gathered would be comparable and that local customs and sensibilities are respected.

Density Experiments: The investigators will conduct experiments stocking fish and shrimp at several densities. The researchers will adapt the details of experimental design to be appropriate to the industry and culture techniques in their region.

Literature Cited
Anggawa, A., 1999. Polyculture of shrimp and tilapia in east Java. American Soybean Association (ASA) Technical Bulletin AQ47-1999.

Fitzsimmons, K., 2001. Polyculture of Tilapia and penaeid shrimp. Global Aquaculture Advocate, 4(3):43­44.

Garcia-Perez, A., D. Alston, and R. Cortes-Maldonado, 2000. Growth, survival, yield and size distribution of freshwater prawn, Macrobrachium rosenbergii, and tilapia, Oreochromis niloticus, in polyculture and monoculture systems in Puerto Rico. J. World Aquacult. Soc., 31(3):446­451.

Samocha, T., A. Lawrence, and D. Pooser, 1998. Growth and survival of juvenile Penaeus vannamei in low salinity water in a semi-closed recirculating system. Isr. J. Aquacult., 5(2):55­59.

Yap, W.G., 2001. The lowdown on world shrimp culture ­ II. INFOFISH International, 2001(3):20­27.



Survey of Tilapia-Shrimp Polycultures in Vietnam and Thailand

New Aquaculture Systems/New Species Research 3A (10NSR3A)/Study/Thailand and Vietnam

Objective
Document the existing tilapia-shrimp polyculture in Thailand and the apparent lack in Vietnam, determine the extent of current and potential applications, and determine which techniques are most successful at this point. Producers in Vietnam and Thailand are desperate to supply the EU market, which has required strict environmentally sensitive culture techniques be used. In preliminary research, Yi has not found any tilapia grown in shrimp ponds in Vietnam. An important question will be why have not the Viet farmers adopted the polyculture.

Significance
Thailand was one of the first shrimp producing areas to develop inland shrimp farms utilizing slightly brackish water. These have been some of the first farms to examine tilapia-shrimp polyculture. AIT has existing relationships in Vietnam that will used to make contacts with producers. Vietnam is the most recent country to experience a shrimp farming boom and the bust appears to be in progress. Vietnam has also seen a boom in interest in tilapia production and we expect that the polyculture will be an important technique. Assisting this growth to occur in a sustainable fashion would be a significant contribution.

Quantified Anticipated Benefits
Hundreds of individual shrimp farms with thousands of employees are impacted by diseases and mismanagement. Many of these farms, their owners, employees or cooperative members could benefit if we can document, develop and extend information relating to a more sustainable polyculture system, compared to the existing model of shrimp farming. The number of farms visited will be documented. The findings of the survey will be shared through workshops and through the regular publications and short-courses presented by AIT.

The polyculture survey will be conducted through face to face interviews with farmers in the shrimp producing regions. We will want to document the number of ponds that have been or are being abandoned due to disease and/or mismanagement. We will also determine who is growing tilapia and shrimp in one of the polyculture systems. The target areas will be the coastal areas of Thailand and Vietnam. AIT has an established relationship with production groups and scientists in Vietnam. Fitzsimmons will attempt to join the survey if it can be scheduled in February or March of 2002.

Regional Integration
AIT is a critical resource to aquaculture in Southeast Asia. They publish findings in newsletters and technical journals. AIT also conducts regular short courses in aquaculture as well as traditional training in degree programs. Dissemination of the survey results should bring the information to aquaculture producers across the region.

Schedule

July 1, 2001 to June 30, 2002
Final report will be submitted by June 30, 2002.

Stocking Densities for Tilapia-Shrimp Polyculture in Thailand

New Aquaculture Systems/New Species Research 3B (10NSR3B)/Experiment/Thailand

Objective
The objective of the trials will be to determine optimal conditions for stocking and rearing tilapia and shrimp in a polyculture system. At AIT, relatively extensive techniques will be tested. These would be most applicable to small farmers who would operate family held or small community ponds with minimal inputs. Replicate small ponds will be stocked to model conditions found in the areas impacted by salinization.

Significance
Thailand has been one of the areas hit the hardest by shrimp pond mismanagement. Development of a sustainable tilapia-shrimp system would contribute to environmental restoration and recovery of lost jobs.

Quantified Anticipated Benefits
We expect to have a detailed plan of how farmers could convert operating or abandoned shrimp ponds to a more sustainable production system. This would benefit the farmers who have had to abandon farms along coastal areas as well as inland locations.

Research Methods
Three treatments in triplicate (9 ponds) will be stocked as follows:

Ponds will be used at the AIT to conduct polyculture trials. Juvenile Penaeus monodon will be stocked at a PL40 stage. Nile tilapia (Oreochromis niloticus) will be stocked at a one-gram average body weight. The 200-m2 ponds previously assigned to PD/A CRSP projects will be utilized for these trials. Salinity levels will be adjusted to 5 ppt. Fish and shrimp will be reared in fertilized ponds following PD/A CRSP guidelines and/or fed with commercially available feeds. The trial will extend for 16 weeks when all animals will be weighed. Average growth and survival will be determined for each treatment. ANOVA will be used to determine if treatment means and survival rats are significantly different

Regional Integration
Thailand has developed aquaculture contacts with Vietnam and will be an important conduit of technology and information.

Schedule

July 1, 2001 to April 30, 2003
Final report will be submitted by April 30, 2003.

Survey of Tilapia-Shrimp Polycultures in Mexico and Honduras

New Aquaculture Systems/New Species Research 3C (10NSR3C)/Study/Mexico and Honduras

This survey will be conducted under the direction of Dr. Contreras from the UJAT. Dr. Fitzsimmons will assist with interviews of tilapia-shrimp polyculture in Northwestern Mexico where he has experience and contacts and in Honduras during the aquaculture meetings.

The objective of this project is to interview shrimp farmers in Mexico and Honduras to document the number of farms being abandoned and why. We would also contact tilapia-shrimp producers in Mexico and Honduras to document details of some basic parameters for stocking and feeding tilapia and shrimp in ponds and raceway systems. Thee results would be published in the scientific literature, at regional and international aquaculture conferences and shared with others who would be interested to implement tilapia-shrimp polycultures.

Significance

Mexico is a major producer of shrimp with numerous farms on both the Pacific and Gulf of Mexico coasts. The impacts of disease and mismanagement have been severe and alternative production systems that are sustainable are critically important. Honduras is still recovering from Hurricane Mitch and a sustainable aquaculture system is needed to speed recovery.

Quantified Anticipated Benefits

Mexico has been hit by diseases almost as severely as many of the South American producers. The White Spot Virus Syndrome has impacted southern Mexico and Honduras and shrimp producers are looking for alternatives to recover profitability. Many of these farms, their owners, employees or cooperative members could benefit if we can document, develop and extend information relating to a more sustainable polyculture system, compared to the existing model of shrimp farming. Tilapia production is established in Honduras and would benefit from addition of another aspect to the industry. Brackish water culture would add to the total volume of tilapia produced and allow for more efficient use of processing and marketing infrastructure. Our plan would be to document the number of farms visited and the number who later implement changes.

Dr. Contreras will use contacts within the aquaculture communities of Southeastern Mexico and PD/A CRSP colleagues in Honduras. This survey will address one of the widest assortments of tilapia-shrimp polycultures. Mexico has extensive shrimp ponds that have been converted to polyculture as well as intensive, controlled aquaculture systems with sequential raceway culture.

Regional Integration

We hope to use this project to improve contacts between UJAT, Zamorano, and University of Arizona. Zamorano will be hosting the Central American Aquaculture Conference in August of 2001. Tilapia and shrimp will be the primary subjects of the conference and will be the forum to jump-start the project. Dissemination of the survey results should bring the information to aquaculture producers across the region.

Schedule
July 1, 2001 to June 30, 2002
Final report will be submitted by June 30, 2002.

Stocking Densities for Tilapia-Shrimp Polyculture in Mexico

New Aquaculture Systems/New Species Research 3D (10NSR3D)/Experiment/Mexico

Objective
The objective of this project is to develop a tilapia-shrimp production system that will be appropriate to the environmental and economic conditions in Mexico and Honduras. Specifically the research team will determine the some basic parameters for stocking and feeding tilapia and shrimp in ponds and raceway systems.

Significance
Mexico has major shrimp and tilapia production areas. Conversion of shrimp to polyculture operations could increase sustainability from environmental and economic perspectives. It could also provide additional employment and food for local markets.

Quantified Anticipated Benefits
Increased production of tilapia from brackish waters and restoration of shrimp ponds to polyculture ponds would be the primary benefit. We hope to quantify this by recording the number of farms that adopt the technology.

Research Methods
Three treatments in triplicate (9 ponds) will be stocked as follows:

Fish and shrimp will be fed with commercially available feeds. Shrimp, (Litopenaeus vannamei) will be stocked into the tanks at a PL40 stage. Nile tilapia (Oreochromis niloticus) will be stocked at a one-gram average body weight. The polycultured animals will be fed at a 10% rate of the total biomass of fish and shrimp per day. The trial will extend for 8 weeks when all animals will be weighed. Average growth and survival will be determined for each treatment. ANOVA will be used to determine if treatment means and survival rats are significantly different

This experiment will be repeated with 40-gram tilapia and 3-gram shrimp to determine how larger fish and shrimp grow in a model of a grow-out system. Feeding rate would be at a 3% rate and the trial will be extended to 12 weeks. Both trials will be conducted at ambient salinity. Additional trials will be conducted with higher salinity levels if time permits. The student will also have the opportunity to gather data from the tilapia-shrimp system at the Genesis farm in Puerto Penasco, Mexico. Fitzsimmons will plan to visit the site in September of 2002.

Regional Integration
Honduras and Panama are regional producers who would benefit from these technologies. Tilapia and shrimp production are growing in the border area of Mexico and the US. Further coordination between US and Mexican scientists and producers is needed. Sharing of graduate students and cooperation on regional conferences are desired goals to improve integration. Through regional aquaculture meetings in Honduras and Mexico and development of e-mail and Web sites, we expect to further integrate aquaculture findings and developments.

Schedule
July 1, 2001 ­ April 30, 2003
Final report will be submitted by April 30, 2003.

Survey of Tilapia-Shrimp Polycultures in Philippines

New Aquaculture Systems/New Species Research 3E (10NSR3E)/Study/Philippines

Objective
The objective is to determine the extent of shrimp farms being abandoned and if any are now experimenting with tilapia-shrimp polyculture. A session at the 2002 Tilapia Conference to be held in Los Baños in the Philippines would be incorporated.

Significance
The Philippines is one of the major producers of both tilapia and shrimp and likely to be one of the major beneficiaries of the development of sustainable polyculture systems.

Quantified Anticipated Benefits
We plan to identify any existing and potential tilapia-shrimp polyculture sites. Methods and production figures would be published and extended to active and potential practitioners of the polyculture.

A scientist from CLSU will customize the general survey questions listed above to the industry in the Philippines. Face to face interviews will be conducted and the results will be published in technical style, but also developed into extension documents that can be shared with potential practitioners. Fitzsimmons will attempt to join the survey if it can be scheduled in February 2002 in conjunction with the Tilapia farming conference.

Regional Integration
We would integrate the findings from the Philippines with those discerned from Thailand and Vietnam. We hope that by sharing the data and techniques between these three major aquaculture producers, more sustainable systems can be developed. There is also interest in exporting tilapia from the Philippines. Brackish water tilapia would be a likely high value product form that should receive a good price on the international markets. This would further integrate the Philippines into the regional markets for tilapia products.

Schedule
July 1, 2001 ­ June 30, 2002
Final report will be submitted by June 30, 2002.

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