Academic literature on the topic 'Prawn farming'

Semi-intensive prawn farming is currently facing difficulties in both the production and consumption processes. Climate change and an unstable output market are the main causes affecting the investment efficiency of semi-intensive prawn farming. The authors carry out the study to evaluate the financial efficiency of semi-intensive prawn farming in My Xuyen District, Soc Trang Province. Research data are collected from 100 households raising prawns. The research results show that, with an average investment cost of 19.8 million VND/1000m2/crop, farmers may earn a profit of 6.5 million VND/1000m2/crop, and the profit margin achieved reaches 0.25 times. Therefore, the model of semi-intensive prawns achieves high financial efficiency and brings a great income for prawn farmers.

This study was conducted through the interview of 48 households applying alternative system of the giant freshwater prawn and shrimp farming in Tra Vinh province. The study aimed to evaluate the effects of different factors on the efficiency of the prawn farming in order to contribute to sustainable development ofthe faming system in the brackish water area of the Mekong Delta. The results showed that the pond was in average area of 0.8 ha; water salinity varied in range of 1-10 ppt during prawn farming. Prawn stocking density was 9.0 inds./m2, and all of the prawn were fed with pellet feed or combined with by-products andtrash fish. After 5, 6 months of culture, average prawn yield of 886 kg/ha/crop and net income of 68 millions VND/ha/crop were achieved. Prawn farming covered only 28.5% of total production cost of the whole system including prawn and tiger shrimp but contributed up to 44.1% of total net income of the prawn -tiger shrimp system. A total of 89.6% of prawn farming households succeeded in getting net income, compared to 81.3% for tiger shrimp farming households. Inaddition, the study also found that factors such as water salinity, pond preparation, seed nursing and feeding methods strongly affect to the efficiency of prawn farming. The result indicated the great potential and feasibility for farming giant freshwater alternatively with tiger shrimp in brackish water areas of the Mekong delta.

A conceptual model of a stochastic production process is proposed which illuminates the business perils associated with shortfalls in yields of aquacultured freshwater prawns. Commercial production data are statistically analyzed within the context of the model to measure the extent to which yield variability engenders financial risks for prawn producers. It is shown that at wholesale prawn prices of US $11.00/kg there is a 50% probability that a representative 8-ha prawn farm utilizing ponds greater than 0.8 surface ha will incur a financial loss in any given year. This probability falls to 30% when ponds smaller than 0.4 surface ha are utilized.

<abstract> <p>Water and soil qualities play significant roles in the farming of giant freshwater prawn. The study evaluated water and soil qualities for giant freshwater prawn farming site suitability by using Analytic Hierarchy Process (AHP) and Geographic Information System (GIS) in Jelebu, Malaysia. The water quality parameters measured were biochemical oxygen demand, chemical oxygen demand, ammonia nitrogen, pH, dissolved oxygen, water temperature, total suspended solids, nitrite concentration and phosphate concentration, meanwhile soil qualities investigated were land use, slope, pH, texture, organic carbon and organic matter. Site suitability analysis can assist to identify the best location for prawn production. Specialist's opinions were used to rank the level of preference and significance of each of the parameter while the pairwise comparison matrix was applied to calculate the weight of each parameter for prawn farming. There are about 45.41% of the land was most suitable, 28.89% was moderately suitable while 25.69% was found unsuitable for prawn farming. The combination of AHP and GIS could give a better database and guide map for planners and decision-makers to take more rewarding decisions when apportioning the land for prawn farming, for better productivity.</p> </abstract>

Bangladesh is considered one of the most suitable countries in the world for freshwater prawn farming because of its favorable agro climatic condition. The expansion of shrimp farming is triggered by the increased international market demand, seed production and intensive shrimp culture. Shrimp farming is having a positive impact on the livelihoods of many people in Bangladesh, especially the poorer farmers. Prawn and shrimp farming offer a reliable source of revenue that is often more profitable than other kinds of farming, or other non-farming employment. The objective of this paper was to review species availability, culture technique and artificial breeding of prawn and shrimp in Bangladesh.Res. Agric., Livest. Fish.4(2): 107-116, August 2017

The objective of this work was to evaluate the chemical composition and fatty acid contents of Amazonian and giant river prawns. After four-month farming, with the same diet for both species, palmitic and stearic acids were the main saturated fatty acids. Oleic acid was the main monounsatured fatty acid, and the eicosapentaenoic and docosahexaenoic acids were the most abundant polyunsaturated acids. Amazonian prawn has higher levels of protein and polyunsaturated fatty acids than those of the giant river prawn, which shows its potential for aquaculture.

Karangsong Village is one of the coastal villages in Indramayu which has a high fishery and marine resources potential, (both capture and aquaculture fisheries). The aquaculture activities in this village were mostly milkfish and prawn cultures. Community development through polyculture activity in this village had been done for 2 years 4 months from December 2012 to April 2015. This activity aimed to improve the community skill, especially milk fish and prawn using polyculture system. Methode used in this activity was training and empowering. The community was trained about pond culture preparation and milk fish and prawn culture methods. The community participated in first year was 4 people, and second year was 9 people. Aid distribution scheme of this program was 1 package for each fish-farmer contained prawn seed, milkfish seed, and fish-prawn feed. Through effectively empowering program, people knowledge, technology, biomass farming, and income (912 million from milkfish farming; 920 million from shrimp farming) were increased.

This paper examines the long-term impacts of the joint prawn-rice gher farming system on agricultural and household incomes, soil fertility, and productivity of modern variety (MV) rice in southwestern Bangladesh, based on socioeconomic data of the gher farmers and soil fertility data of their gher plots. In 2005, 20 farmers operating on 30 plots were randomly selected from the Bilpabla village of Khulna from whom prawn and MV rice production data were collected using a questionnaire; soil samples were also collected and tested. In 2011 and 2017, the sustainability of the gher system over time was assessed through another survey of farmers following the same methodology. Results revealed that although the nominal income from gher farming increased by 59 percent in 2011 and 23 percent in 2017, the real income and per capita household income remained unchanged over time. Agricultural income has contributed about 65 percent to household income, which for gher farmers was about 200 percent higher than average rural incomes in Bangladesh. Rice productivity declined slightly from its 2005 level. However, the productivity of MV rice under prawn-rice gher farming is substantially higher than in the conventional MV rice farming system. The positive estimates of the Mean Soil Quality Index and Soil Degradation Index for land used for MV paddy production within the gher indicate an increase in soil nutrients. This suggests that the joint prawn-rice gher farming system is relatively sustainable, having improved soil fertility and stabilized real income. Policy implications toward promoting agricultural growth in the southwestern region of Bangladesh include research on developing varieties of MV rice suited to prawn-rice gher farming and the development of commercial feeds and markets for prawn to further raise productivity and incomes of gher farmers.

The overarching aim of this research was to improve understanding of the synergies and trade-offs between economic and domestic food security benefits associated export-oriented shrimp and prawn aquaculture in a fragile developing country environmental context. The research scope covers the entire ‘seafood system’ incorporating production, distribution, trading and consumption in the south-west coastal region under greater Khulna District, Bangladesh. The primary research objective was to understand causal factors in variation of seafood nutritional quality and health outcomes, exploring correlations with seafood consumption across a range of agro-ecological, aquatic farming systems and socio-economic conditions. The study also focused on differences in intra-household allocation with a special focus on adolescent girls, being amongst the most vulnerable members of society. These objectives necessitated a highly inter-disciplinary approach to understand complex interactions between biophysical aspects (e.g. where and which species are most effective in supplying essential nutrients) and the social norms of food allocation. Fieldwork was conducted in Satkhira, Khulna, and Bagerhat Districts of Khulna Province over 17 months during 2012 to 2015. Four villages across a peak-annual surface water salinity gradient; high saline (>10 ppt), medium saline (>5<10 ppt), low saline (<5 ppt) and freshwater (<0.5 ppt) were selected for case-studies. The thesis begins with a literature review of the evolution of shrimp and prawn farming in Bangladesh and the wider region and identification of knowledge gaps. Research resolved from district to community to household level. Key informant (KI) interviews were used to establish well-being criteria (based on a range of 5 social and economic assets) at community level. In each community a census of households (n=1082 households) were derived from the same interviews and KIs asked to ranked households on the established well-being criteria. Results were validated through a short interview of all the identified households (HH). This sample-frame provided the based for two concurrent survey efforts. Stratified-random selection of 160 HH on two well-being categories (better-off and worse-off) for ‘farm level’ analysis using a semi-structured questionnaire. Key topics included inputs/outputs characteristics, economic benefits and the fate of farmed products were evaluated. Another 240 households with single adolescent girls were selected from the same frame, again with randomized-stratified sampling based on well-being categories for ‘intra-household’ analysis. This resulted in selection of 60 HH per community consisting of 30 ‘better-off’ and 30 worse-off households (further analysis was conducted on a range of secondary sampling outcomes based on livelihood options, intra-household food distribution and aquatic farming assets). A 24-hour food recall method, food frequency questionnaire, food photography and measuring cup sets were used to estimate individual members’ food consumption at the household level. Anthropometric measures (stunting, wasting, BMI, MUAC) and biomarkers (omega-3 index in RBC and LC n-3 PUFA/LC PUFA in whole blood cell) were used to assess food security outcomes of adolescent girls (n=200 subject). In an entirely separate effort, samples of shrimp/prawn and fish polyculture species (57 species and 9 by-products, 1 live feed; n=672) were collected from the major agro-ecologies (four saline gradients; HS, MS, LS and FW) and culture systems (extensive, semi-intensive, intensive, organic and pocket gher). At least 3 sites from each saline gradient (3×4=12 sites) were selected for sampling and pooled samples to represent all the culture system in the region. The major macro and micronutrients of the collected species were analysed and these datasets were used to know the nutritional distribution among the family members in household level study. Two aggregate indices of wealth (or well-being) and aquaculture were developed based on a range of quantitative (ordinal and interval) measures. Principle Component Analysis (PCA) was used to understand how aquaculture influences on wealth gain. Wealth index of the same social well-being did not differ among the agro-ecologies. However, the aquaculture index was varied in agro-ecologies. Most of the households (60-80%) were involved directly in aquaculture however, a majority portion of the households was worse-off (48-64%). Both HS and LS area had more livelihood options due to their proximity to mangrove forest Sundarbans and city amenities, respectively compared to MS and FW area. Ownership of the land did not influence any involvement in aquaculture and yields but he willingness and risk-absorbing capacity of the farmers were the main factor to get involve in aqauculture. In aquatic farming system the importance of export-oriented shellfish yield gradually decreased from HS to FW area (55-20% by volume). The intentional stocking of finfish and PLs were common across the saline areas however the wild caught juveniles and hatchery originated fingerlings were usual in higher and lower saline areas, respectively. The low priced tilapia took the place of wild recruited mangrove fishes in MS area. Diseases, especially the devastating white spot virus (WSSV), frequency were higher in higher saline areas. The indicators like wild recruitment, salinity, water productivity and water management also a vital factor to gain yield. The integration of aquatic and terrestrial crops (rice and dyke crop) in the lower saline areas provide higher yield compared to higher saline areas. However, the net economic returns were largely determined by the aquatic products. The income of ghers in FW and MS area was sensitive to the lower prices of freshwater finfish and tilapia. The protein content in shellfish was higher than the other finfish, however, lower in other essential nutrients. Species living in the higher saline areas contained higher total n-3 PUFA (in weight) and LC n-3 PUFA/LC-PUFA compared to the same species living in lower saline areas. Small Indigenous Species (SIS) and Self-Recruiting Species (SRS) were proven to provide higher micronutrients and total n-3 PUFA than larger fish. Seafood that destined for the international markets contained less n-3 PUFA and micronutrients in comparison to the domestically consumed fish. Customary intra-household food distribution disparity (mainly fish) still exists at household levels where females, especially adolescent girls, were deprived. Fish consumption (>77 g /capita/day) and fish originated protein supply (>25% of total protein intake) was higher than the other part of Bangladesh. The protein consumption of adolescents was 2-3 times higher than the Recommended Nutritional Intake (RNI). However, the energy intake was lower than the required level. High protein, low energy consumption was not reflected in body mass. Micronutrients (zinc) consumption was above the RNI level. However, iron and calcium consumption was less than the RNI. The n-3 PUFA in RBC of adolescent girls accurately reflected their access to, and availability of, oily fish. In the omega-3 index (n-3 PUFA in red blood cell) both HS and MS areas, adolescent females were in the intermediate stage (4-8%), and rest of the two areas were in the undesirable stage (<4%). The n-3 LC-PUFA was around 20-30% of total LC-PUFA content in whole blood and gradually decreased from higher saline to lower saline areas. The thesis concludes that the gher based aquatic animal farming in S-W Bangladesh is a dynamic system operated by both rich and poor. The salinity level and the presence of mangrove forest make the farming system dynamic. The holistic scenario suggested aquaculture in ghers is a family driven small scale polyculture where varieties of aquatic foods are produced both for global and local value chain. Higher amounts of valued products (both in terms of nutrition and price), less disease susceptibility, more alternative livelihood options both in HS and LS were found in better position than the other two sites, however the nutritional content of fish and its manifestation in adolescents strongly mirrors agro-ecologies irrespective of social position of households. The thesis provides an important, grounded importance of the system and the linkage of the community people for livelihoods, food production and food security. The dynamic systems were understood and effective messages formulated for the policy makers. In doing so, the thesis contributes to an understanding of how small-scale polyculture equally benefited local food security and macroeconomic growth of a developing country.

The assemblage composition, biomass and dynamics of zooplankton and epibenthos were examined in a commercial prawn pond in southeast Queensland over two seasons. Physico-chemical characteristics of the pond water were measured concurrently. Numbers and biomass of zooplankton in the surface tows (140 micrometre mesh) varied from 8 ind. L-1 (44 micrograms L-1) to 112 ind. L-1 (324 micrograms L-1) in the first season, with peaks in biomass corresponding to peaks in numbers. In the second season the zooplankton numbers varied from 12 to 590 ind. L-1, but peaks in numbers did not correspond with peaks in biomass, which varied from 28 to 465 micrograms L-1. This was due to differences in the size of the dominant taxa across the season. Although this occurred in both seasons, the effect on biomass was more pronounced in the second season. In both seasons, immediately after the ponds were stocked with prawn postlarvae there was a rapid decline in zooplankton numbers, particularly of the dominant larger copepods. This was probably due to predation by the postlarvae. Subsequent peaks in zooplankton numbers were principally due to barnacle nauplii. The largest peaks in zooplankton numbers occurred before stocking in the first season, but the largest peaks were in the middle of the second season. While changes in abundance and biomass of the zooplankton assemblage were not correlated with physico-chemical characteristics in the first season, there were correlations between zooplankton numbers and temperature, dissolved oxygen, pH and secchi disk readings in the second season. No correlations were found with zooplankton biomass and physico-chemical characteristics in the second season. The correlations in the second season were mainly due to the high prevalence of barnacle nauplii through the middle part of the season, and may reflect suitable conditions for barnacle reproduction. Epibenthic faunal abundance in the beam trawls (1 mm mesh) peaked at 14 ind. m-2 and 7 ind. m-2 in the first and second seasons respectively and the biomasses at 0.8 g m-2 and 0.7 g m-2. Peaks in abundance of epibenthos did not correspond to peaks in biomass. This was due to large differences in the size of the taxa across the seasons. Sergestids (Acetes sibogae) and amphipods were the most abundant taxa in beam trawl samples. Amphipods were only abundant in the first season, with their numbers increasing towards the end of the grow out period. Acetes were abundant in both seasons, but were dominant in the second season. Correlations between physico-chemical parameters and epibenthos numbers were found to be strongly influenced by the dominant taxa in each season. In the first season, negative correlations were found between epibenthos abundance and pH and temperature. These relationships may reflect an effect on the growth of macroalgae in the pond, with which the amphipods were strongly associated, rather than a direct effect on the epibenthos. In the second season, a positive correlation existed between temperature and epibenthos abundance, however this was strongly influenced by the very high abundance of Acetes in the last sampling period. No correlations were found between epibenthic fauna biomass and physico-chemical parameters. Abundances of epibenthic fauna were not related to zooplankton densities indicating this source of food was not likely to be a limiting factor. Neither the pond water exchange regime nor moon phase could explain changes observed in abundances of zooplankton or epibenthos assemblages in the first season, however the sampling regime was not designed to specifically investigate these effects. In the second season water exchanges were sampled more rigorously. The density of zooplankton in the outlet water was from 2 to 59% of the density of zooplankton in the pond, and the zooplankton density of the inlet water was from 9 to 50% of the outlet water. The number of zooplankton recruited into the pond from the inlet water, after the prawns were stocked, was negligible and contributed little to changes observed in zooplankton assemblages. Reproduction of barnacles within the pond appeared to play the most important role in changes in the assemblage. Water exchange did, however, appear to play a greater role in the changes observed in epibenthic fauna assemblages. In the last season of sampling the feeding of the dominant epibenthic species, Acetes sibogae, was examined using a combination of gut content and stable isotope analysis. Acetes gained little nutrition directly from the pelleted feed, probably relying primarily on zooplankton as their direct food source. Other dietary items such as macroalgae also played a role in the nutrition of the Acetes. If Acetes numbers were high at the beginning of a season they may compete with the newly stocked prawns for the zooplankton resource. However, they will not compete with the prawns later in the season when the prawns are gaining most of their nutrition from the pelleted feed. Overall it appears that zooplankton are important to the nutrition of the prawns at the beginning of the season when the assemblage is usually dominated by copepods. Later in the season the assemblage is dominated by barnacle nauplii which are recruited from within the pond. The establishment of an abundant assemblage of suitable zooplankton species before stocking prawn postlarvae would appear to be beneficial, if not essential. The assemblage of epibenthic fauna changes throughout the season as new recruits are brought in from outside the pond. Epibenthic faunal assemblages in ponds from southeast Queensland are dominated by Acetes which are not likely to adversely affect the production of prawns unless they are particularly abundant early in the grow out season when the prawns would be utilising the same food resources as Acetes.

The assemblage composition, biomass and dynamics of zooplankton and epibenthos were examined in a commercial prawn pond in southeast Queensland over two seasons. Physico-chemical characteristics of the pond water were measured concurrently. Numbers and biomass of zooplankton in the surface tows (140 micrometre mesh) varied from 8 ind. L-1 (44 micrograms L-1) to 112 ind. L-1 (324 micrograms L-1) in the first season, with peaks in biomass corresponding to peaks in numbers. In the second season the zooplankton numbers varied from 12 to 590 ind. L-1, but peaks in numbers did not correspond with peaks in biomass, which varied from 28 to 465 micrograms L-1. This was due to differences in the size of the dominant taxa across the season. Although this occurred in both seasons, the effect on biomass was more pronounced in the second season. In both seasons, immediately after the ponds were stocked with prawn postlarvae there was a rapid decline in zooplankton numbers, particularly of the dominant larger copepods. This was probably due to predation by the postlarvae. Subsequent peaks in zooplankton numbers were principally due to barnacle nauplii. The largest peaks in zooplankton numbers occurred before stocking in the first season, but the largest peaks were in the middle of the second season. While changes in abundance and biomass of the zooplankton assemblage were not correlated with physico-chemical characteristics in the first season, there were correlations between zooplankton numbers and temperature, dissolved oxygen, pH and secchi disk readings in the second season. No correlations were found with zooplankton biomass and physico-chemical characteristics in the second season. The correlations in the second season were mainly due to the high prevalence of barnacle nauplii through the middle part of the season, and may reflect suitable conditions for barnacle reproduction. Epibenthic faunal abundance in the beam trawls (1 mm mesh) peaked at 14 ind. m-2 and 7 ind. m-2 in the first and second seasons respectively and the biomasses at 0.8 g m-2 and 0.7 g m-2. Peaks in abundance of epibenthos did not correspond to peaks in biomass. This was due to large differences in the size of the taxa across the seasons. Sergestids (Acetes sibogae) and amphipods were the most abundant taxa in beam trawl samples. Amphipods were only abundant in the first season, with their numbers increasing towards the end of the grow out period. Acetes were abundant in both seasons, but were dominant in the second season. Correlations between physico-chemical parameters and epibenthos numbers were found to be strongly influenced by the dominant taxa in each season. In the first season, negative correlations were found between epibenthos abundance and pH and temperature. These relationships may reflect an effect on the growth of macroalgae in the pond, with which the amphipods were strongly associated, rather than a direct effect on the epibenthos. In the second season, a positive correlation existed between temperature and epibenthos abundance, however this was strongly influenced by the very high abundance of Acetes in the last sampling period. No correlations were found between epibenthic fauna biomass and physico-chemical parameters. Abundances of epibenthic fauna were not related to zooplankton densities indicating this source of food was not likely to be a limiting factor. Neither the pond water exchange regime nor moon phase could explain changes observed in abundances of zooplankton or epibenthos assemblages in the first season, however the sampling regime was not designed to specifically investigate these effects. In the second season water exchanges were sampled more rigorously. The density of zooplankton in the outlet water was from 2 to 59% of the density of zooplankton in the pond, and the zooplankton density of the inlet water was from 9 to 50% of the outlet water. The number of zooplankton recruited into the pond from the inlet water, after the prawns were stocked, was negligible and contributed little to changes observed in zooplankton assemblages. Reproduction of barnacles within the pond appeared to play the most important role in changes in the assemblage. Water exchange did, however, appear to play a greater role in the changes observed in epibenthic fauna assemblages. In the last season of sampling the feeding of the dominant epibenthic species, Acetes sibogae, was examined using a combination of gut content and stable isotope analysis. Acetes gained little nutrition directly from the pelleted feed, probably relying primarily on zooplankton as their direct food source. Other dietary items such as macroalgae also played a role in the nutrition of the Acetes. If Acetes numbers were high at the beginning of a season they may compete with the newly stocked prawns for the zooplankton resource. However, they will not compete with the prawns later in the season when the prawns are gaining most of their nutrition from the pelleted feed. Overall it appears that zooplankton are important to the nutrition of the prawns at the beginning of the season when the assemblage is usually dominated by copepods. Later in the season the assemblage is dominated by barnacle nauplii which are recruited from within the pond. The establishment of an abundant assemblage of suitable zooplankton species before stocking prawn postlarvae would appear to be beneficial, if not essential. The assemblage of epibenthic fauna changes throughout the season as new recruits are brought in from outside the pond. Epibenthic faunal assemblages in ponds from southeast Queensland are dominated by Acetes which are not likely to adversely affect the production of prawns unless they are particularly abundant early in the grow out season when the prawns would be utilising the same food resources as Acetes.
Thesis (Masters)
Master of Philosophy (MPhil)
School of Environmental and Applied Science
Full Text

Acute hepatopancreatic necrosis disease (AHPND) is an emerging bacterial infection in shrimp that has been widespread across the major world shrimp producing countries since 2009. AHPND epizootics have resulted in a huge loss of global shrimp production, similar to that caused by white spot disease in the 1990’s. The epizootiological understanding of the spread of AHPND is still in its early stages, however, and most of the currently published research findings are based on experimental studies that may struggle to capture the potential for disease transmission at the country scale. The main aim of this research, therefore, is to develop epizootiological tools to study AHPND transmission between shrimp farming sites. Some tools used in this research have already been applied to shrimp epizoology, but others are used here for the first time to evaluate the spread of shrimp diseases. According to an epizootiological survey of AHPND in Thailand (Chapter 3), the first case of AHPND in the country was in eastern shrimp farms in January 2012. The disease was then transmitted to the south in December 2012. The results obtained from interviews, undertaken with 143 sample farms were stratified by three farm-scales (large, medium and small) and two locations (east and south). Both the southern location and large-scale farming were associated with a delay in AHPND onset compared with the eastern location and small- and medium-scale farming. The 24 risk factors (mostly related to farming management practices) for AHPND were investigated in a cross-sectional study (Chapter 3). This allowed the development of an AHPND decision tree for defining cases (diseased farms) and controls (non-diseased farms) because at the time of the study AHPND was a disease of unknown etiology. Results of univariate and unconditional logistic regression models indicated that two farming management practices related to the onset of AHPND. First, the absence of pond harrowing before shrimp stocking increased the risk of AHPND occurrence with an odds ratio () of 3.9 (95 % CI 1.3–12.6; P‑value = 0.01), whereas earthen ponds decreased the risk of AHPND with an of 0.25 (95 % CI 0.06–0.8; P‑value = 0.02). These findings imply that good farming management practices, such as pond-bottom harrowing, which are a common practice of shrimp farming in earthen ponds, may contribute to overcoming AHPND infection at farm level. For the purposes of disease surveillance and control, the structure of the live shrimp movement network within Thailand (LSMN) was modelled, which demonstrated the high potential for site-to-site disease spread (Chapter 4). Real network data was recorded over a 13-month period from March 2013 to March 2014 by the Thailand Department of Fisheries. After data validation, c. 74 400 repeated connections between 13 801 shrimp farming sites were retained. 77 % of the total connections were inter-province movements; the remaining connections were intra-province movements (23 %). The results demonstrated that the LSMN had properties that both aided and hindered disease spread (Chapter 4). For hindering transmission, the correlation between and degrees was weakly positive, i.e. it suggests that sites with a high risk of catching disease posed a low risk for transmitting the disease (assuming solely network spread), and the LSMN showed disassortative mixing, i.e. a low preference for connections joining sites with high degree linked to connections with high degree. However, there were low values for mean shortest path length and clustering. The latter characteristics tend to be associated with the potential for disease epidemics. Moreover, the LSMN displayed the power-law in both and degree distributions with the exponents 2.87 and 2.17, respectively. The presence of power-law distributions indicates that most sites in the LSMN have a small number of connections, while a few sites have large numbers of connections. These findings not only contribute to a better understanding of disease spread between sites, therefore, but also reveal the importance of targeted disease surveillance and control, due to the detection of scale-free properties in the LSMN. Chapter 5, therefore, examined the effectiveness of targeted disease surveillance and control in respect to reducing the potential size of epizootics in the LSMN. The study untilised network approaches to identify high-risk connections, whose removal from the network could reduce epizootics. Five disease-control algorithms were developed for the comparison: four of these algorithms were based on centrality measures to represent targeted approaches, with a non-targeted approach as a control. With the targeted approaches, technically admissible centrality measures were considered: the betweenness (the number of shortest paths that go through connections in a network), connection weight (the frequency of repeated connections between a site pair), eigenvector (considering the degree centralities of all neighbouring sites connected to a specified site), and subnet-crossing (prioritising connections that links two different subnetworks). The results showed that the estimated epizootic sizes were smaller when an optimal targeted approach was applied, compared with the random targeting of high-risk connections. This optimal targeted approach can be used to prioritise targets in the context of establishing disease surveillance and control programmes. With complex modes of disease transmission (i.e. long-distance transmission like via live shrimp movement, and local transmission), an compartmental, individual-based epizootic model was constructed for AHPND (Chapter 6). The modelling uncovered the seasonality of AHPND epizootics in Thailand, which were found likely to occur between April and August (during the hot and rainy seasons of Thailand). Based on two movement types, intra-province movements were a small proportion of connections, and they alone could cause a small AHPND epizootic. The main pathway for AHPND spread is therefore long-distance transmission and regulators need to increase the efficacy of testing for diseases in farmed shrimp before movements and improve the conduct of routine monitoring for diseases. The implementation of these biosecurity practices was modelled by changing the values of the long-distance transmission rate. The model demonstrated that high levels of biosecurity on live shrimp movements (1) led to a decrease in the potential size of epizootics in Thai shrimp farming. Moreover, the potential size of epizootics was also decreased when AHPND spread was modelled with a decreased value for the local transmission rate. Hence, not only did the model predict AHPND epizootic dynamics stochastically, but it also assessed biosecurity enhancement, allowing the design of effective prevention programmes. In brief, this thesis develops tools for the systematic epizootiological study of AHPND transmission in Thai shrimp farming and demonstrates that: (1) at farm level, current Thai shrimp farming should enhance biosecurity systems even in larger businesses, (2) at country level, targeted disease control strategies are required to establish disease surveillance and control measures. Although the epizootiological tools used here mainly evaluate the spread of AHPND in shrimp farming sites, they could be adapted to other infectious diseases or other farming sectors, such as the current spread of tilapia lake virus in Nile tilapia farms.

Submitted by JOSUÉ FERNANDES FROTA FILHO (frotafilho.jf@outlook.com) on 2018-04-24T17:00:58Z No. of bitstreams: 1 Josue_Dissertação_24_04_FINAL.pdf: 705810 bytes, checksum: c7f70d2764da25e302dc2b38af6c84bd (MD5)
Rejected by Alexandra Maria Donadon Lusser Segali null (alexmar@fcav.unesp.br), reason: Solicitamos que realize correções na submissão seguindo as orientações abaixo: O arquivo pdf submetido ao repositório deve conter a ficha catalográfica e o certificado de aprovação (documentos obrigatórios). Favor inserir no arquivo pdf a ficha catalográfica e o certificado de aprovação (tudo em um arquivo só). Agradecemos a compreensão. on 2018-04-25T12:56:05Z (GMT)
Submitted by JOSUÉ FERNANDES FROTA FILHO (frotafilho.jf@outlook.com) on 2018-04-26T11:48:21Z No. of bitstreams: 1 Josue_Dissertação_24_04_FINAL corrigido.pdf: 927542 bytes, checksum: a658dd423a96120871bc91bfa99cbc9b (MD5)
Approved for entry into archive by Alexandra Maria Donadon Lusser Segali null (alexmar@fcav.unesp.br) on 2018-04-26T12:10:28Z (GMT) No. of bitstreams: 1 fotafilho_jf_me_jabo.pdf: 927542 bytes, checksum: a658dd423a96120871bc91bfa99cbc9b (MD5)
Made available in DSpace on 2018-04-26T12:10:28Z (GMT). No. of bitstreams: 1 fotafilho_jf_me_jabo.pdf: 927542 bytes, checksum: a658dd423a96120871bc91bfa99cbc9b (MD5) Previous issue date: 2018-04-19
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
O crescimento acelerado da aquicultura vem sendo acompanhado pela crescente preocupação em se garantir a sustentabilidade das atividades aquícolas. A sustentabilidade neste trabalho é baseada principalmente em duas dimensões: ambiental, e econômica. O presente trabalho teve como objetivo avaliar a sustentabilidade ambiental e a viabilidade econômica em pequena escala de produção de pós-larvas do camarão de água doce da espécie Macrobrachium amazonicum, por meio de um conjunto indicadores de sustentabilidade. Foram considerados os ciclos de produção durante um ano de cultivo de pós-larvas do camarão-da-amazônia. A capacidade produtiva considerada foi de 290 milheiros de pós-larvas/mês. A sustentabilidade ambiental foi medida com base na utilização de recursos naturais, eficiência no uso destes recursos e poluição liberada ao ambiente pelo meio de cultivo. A sustentabilidade econômica foi medida com base nos aspectos sobre a eficiência no uso dos recursos financeiros e a capacidade de gerar recursos para reinvestimentos na atividade. Os resultados sugerem que há viabilidade econômica para o produtor que realiza larvicultura em sistemas de fundo de quintal (backyard hatchery). Além disso, os dados obtidos também mostraram que embora a larvicultura seja uma atividade bastante intensificada, há eficiência na utilização dos recursos naturais, sendo mais sustentável do que outras fases de produção, como o berçário e crescimento final da mesma espécie. Desse modo, o modelo utilizado é uma alternativa viável com sustentabilidade econômica e ambiental para produção de pós-larvas de M. amazonicum em sistemas familiares de produção.
The rapid growth of aquaculture has been accompanied by the increasing concern to ensure sustainability of aquatic activities. In this work, sustainability is based on environmental and economic dimensions. The objective of the study is to evaluate the environmental and economic sustainability of a small scale Macrobrachium amazonicum post-larvae production using a set of indicators for sustainability. Production cycles during one year of the Amazon Prawn hatchery was considered. The considered productive capacity was 290 thousand post larvae/month. Environmental sustainability measurements were based on the use of natural resources, efficiency in the use of resources and pollution released to environment from the production facility. Economic sustainability measurements were based on the aspects of efficiency in the use of financial resources and the capacity to generate resources for reinvestments in the activity. Results show that there is economic feasibility for the ‘backyard’ hatcheries system for freshwater prawn farmers. In addition, data indicate that in spite of hatchery being a highly intensified activity, there is efficiency in using natural resources, and it is more sustainable than other production phases, such as nursery and grow-out phase of the same species. To sum it up, the hatchery model studied is a feasible and sustainable alternative to produce M. amazonicum post-larvae with environmental and economic sustainability to be operated using either family labour production.
88882.156917/2017-01

This chapter focuses on advances in the farm production of the freshwater prawns (FWPs) Macrobrachium spp., primarily on M. rosenbergii. Farming FWPs is generally divided into four phases: reproduction, hatchery, nursery, and grow-out. The broodstock is held in earthen ponds or indoor tanks filled with freshwater. The hatchery is usually performed in intensive systems, using indoor tanks and brackish water, whereas the nursery phase uses freshwater in indoor tanks or in earthen ponds. The grow-out is generally performed in semi-intensive systems, using freshwater earthen ponds in monoculture, but integrated systems with fish, crabs, or rice are also very common. The production strategy is site specific and should be set up according to the species raised, climate characteristics, and the desired market size of the prawn. Productivity generally ranges from 1,000 to 4,500 kg/ha/yr, but may surpass 11,000 kg/ha/yr in tropical areas. Production is concentrated in Asia, mainly in China. Most production is traded in local markets, and FWPs are usually sold alive, but some countries, such as Bangladesh, India, and Thailand, export frozen prawns to Europe and the USA. Substantial scientific literature and more than 100 patents support the technology for farming FWPs. However, genetics, nutrition, and interaction with other species in integrated culture are still issues. The culture of FWPs has been described in detail in a number of international review papers, books and book chapters, and practical manuals. This chapter summarizes and updates the information found in those publications.