Bac Lieu Research Articles

Research on assessment of suface water environment and sediment in seawater shallow area in Bac Lieu Province and proposing solutions for protection

Research on assessment of suface water environment and sediment in seawater shallow area in Bac Lieu Province and proposing solutions for protection

Risk factors associated with acute hepatopancreatic necrosis disease at shrimp farm level in Bac Lieu Province, Vietnam.

Background and Aim:Acute hepatopancreatic necrosis disease (AHPND) is a severe disease in shrimp farms and adversely affected the shrimp industry of Vietnam. So far, the study on risk factors associated with AHPND outbreaks is limited. The objective of this study was to determine the potential risk factors of AHPND at the shrimp farm level in Bac Lieu Province, Vietnam.Materials and Methods:Real-time-Polymerase chain reaction was used to analyze data collected from an active surveillance program of shrimp farms in 2017 in the Vinh Tien and Vinh Lac villages, Vinh Thinh commune, Hoa Binh district in Bac Lieu Province, Vietnam. The matched case-control study selected 20 cases and 20 control farms from 134 shrimp farms. In 2018, face-to-face interviews using structured questionnaires were conducted with the farmers of these selected farms.Results:Of the 59 studied variables, seven had p≤0.2 based on bivariate analyses. The results of multivariable analysis showed that the presence of fish-eating birds on shrimp farms was a significant association with AHPND (odds ratio=8, p=0.049).Conclusion:To reduce the effect of AHPND, farmers should apply effective methods to manage wild animals such as using a grid or net to cover the pond, combined with improved biosecurity.

Using games to improve learning vocabulary for non-English-majored students at Bac Lieu university

The fact is that teaching and learning vocabulary is one of the most complicated problems, and the traditional way of vocabulary instructions proves ineffective, and even worse, decreasing students’ interest and motivations in their study and work. An experimental case study was conducted with two respective classes at Bac Lieu University, Vietnam. Accordingly, in one experimental class, vocabulary was taught with the cooperative vocabulary games at the practice and revision stages. The results revealed that games could be used to improve non-English-majored students’ learning vocabulary at Bac Lieu University because of its following major effects. Firstly, games brought in relaxation and fun for students, thus helped them learn and retain new words more easily. In other words, students could be more interested in learning the vocabulary. Secondly, games usually involved friendly competition and they kept learners interested. These created the motivation for learners of English to get involved and participated actively in the learning activities. Finally, games created meaningful contexts for language practice. The more they practiced the more they could use the words. Then they learnt better and had higher results in their achievement as well.

ENGLISH-MAJORED STUDENTS’ MOTIVATION IN ENGLISH LANGUAGE LEARNING AND THEIR USE OF READING STRATEGIES: RESEARCH PERSPECTIVES

Reading plays a vital role in improving second/foreign language learning as it can encourage the development of autonomous learners. Furthermore, ESL/EFL learners’ use of reading strategies can be affected by their learning motivation, which can result in the high or low frequent use of reading strategies in reading comprehension. The present study, therefore, investigated the motivation in English language learning and the use of reading strategies among English-majored freshmen at a university in Bac Lieu province, Vietnam. A questionnaire was used to collect data from 180 English-majored freshmen, six of whom took part in semi-structured interviews. The results showed that participants had a high level of motivation in English language learning, and their metacognitive strategies worked better with their reading comprehension than their cognitive and social/affective strategies. The study further unraveled that the more participants were motivated in English language learning, the more they employed metacognitive and cognitive strategies in reading comprehension.

Some biological parameters of Glossogobius aureus population from the Mekong Delta

Glossogobius aureus is an important commercial fish for food supply and has been caught increasingly, but data on its population biology is limited. The present study was carried out along coastlines from Soc Trang to Bac Lieu, southern Vietnam to contribute new information on the biological characteristics of G. aureus population. Data analysis of length-frequency distribution of 666 individuals showed that the equation of von Bertalanffy curve of this species was . The species displayed 4.47 y longevity and 2.75 in the growth performance. The length-converted catch curve analysis showed that the fishing, natural and total mortalities were 2.73 yr-1, 1.52 yr-1 and 4.25 yr-1 respectively and fish exploitation rate was 0.64. There was one recruitment peak in July and the analyses of relative yield-per-recruit and biomass-per-recruit gave Emax=0.408, E0.1=0.284 and E0.5=0.404. This goby is potentially an aquaculture species due to its high growth rate. The fish stock has been overfished, so the gill net mesh size should be increased and fish should not be caught during the recruitment period for sustainable management.

Assessment of meteorological drought in the Vietnamese Mekong delta in period 1985-2018

Drought is one of a major natural disaster that causes tremendous damage to the ecological environment and social-economic in the Vietnamese Mekong Delta (VMD). Drought characteristics are invaluable knowledge for better management of water resources and agriculture production, especially under climate change context. This study investigated the spatiotemporal trend, intensity, duration, and frequency of meteorological droughts over VMD by using the Standardized Precipitation Evaporation Index (SPEI). The SPEI at multiple time scales (3, 6 and 12 months) are determined by using the monthly precipitation and temperature data between 1985 and 2018 obtained from ten meteorological stations in VMD namely Ba Tri, Cang Long, Soc Trang, Bac Lieu, Rach Gia, Ca Mau, Chau Doc, Can Tho, Cao Lanh, and My Tho. SPEI detected ten extreme drought events from 1985-2018 that matches with the historical extreme drought events reported in VMD. It means SPEI could be a useful indicator to support for drought management and mitigation in the future. The extreme drought event from October 2013 to September 2016 was the highest intensity and most prolonged duration from 1985-2018. The El Niño is considered to strongly influence on extreme drought events in VMD as all extreme drought events are highly associated with El Niño periods. The intensity, duration and frequency of drought events increased from 1985 to 2018. Drought events are more severe in VMD in recent years. Extreme drought also tends to cover for over VMD region. Adaption measures are essential to cope with drought disaster, especially in the agricultural and aquacultural sectors.

Roles of thermospheric neutral wind and equatorial electrojet in pre-reversal enhancement, deduced from observations in Southeast Asia

Previous studies have proposed that both the thermospheric neutral wind and the equatorial electrojet (EEJ) near sunset play important roles in the pre-reversal enhancement (PRE) mechanism. In this study, we have used observations made in the equatorial region of Southeast Asia during March–April and September–October in 2010–2013 to investigate influences of the eastward neutral wind and the EEJ on the PRE’s strength. Our analysis employs data collected by the Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) satellite to determine the zonal (east-west direction) neutral wind at an altitude of ~250 km (bottomside F region) at longitudes of 90°–130°E in the dusk sector. Three ionosondes, at Chumphon (dip lat.: 3.0°N) in Thailand, at Bac Lieu (dip lat.: 1.7°N) in Vietnam, and at Cebu (dip lat.: 3.0°N) in Philippines, provided the data we have used to derive the PRE strength. Data from two magnetometers — at Phuket (dip lat.: 0.1°S) in Thailand and at Kototabang (dip lat.: 10.3°S) in Indonesia — were used to estimate the EEJ strength. Our study is focused particularly on days with magnetically quiet conditions. We have found that the eastward neutral wind and the EEJ are both closely correlated with the PRE; their cross-correlation coefficients with it are, respectively, 0.42 and 0.47. Their relationship with each other is weaker: the cross-correlation coefficient between the eastward neutral wind and the EEJ is just 0.26. Our findings suggest that both the eastward neutral wind and the EEJ near sunset are involved in the PRE mechanism. Based on the weak relationship between these two parameters, however, they appear to be significantly independent of each other. Thus, the wind and the EEJ are likely to be influencing the PRE magnitude independently, their effects balancing each other.

Participatory selection of CWR‐derived salt‐tolerant rice lines adapted to the coastal zone of the Mekong Delta

AbstractClimate change is affecting agricultural production in the coastal areas of the Mekong Delta through the intrusion of salinity into the rice (Oryza spp.) fields, where farmers cultivate photoperiod‐sensitive rice varieties with long growth duration and low grain yields. A set of 12 stable crop wild relative (CWR)‐derived rice lines with introgressions from wild rice Oryza rufipogon Griffiths and O. nivara S.D. Sharma & Shastry was evaluated for their phenotypic response to salinity tolerance by a participatory selection approach on farm in the Phuoc Long and Gia Rai districts, Bac Lieu province. The evaluation of the results showed that four lines derived from CWR are well adapted to the local environmental conditions, with high grain yield (>6.5 t ha−1), early maturity, and short plant height. These CWR‐derived lines were adopted by farmers and proposed for testing on a larger scale in different areas of the coastal zone.

SURVEYING THE CURRENT SITUATION OF USING PROBIOTICS, CONTROLLING DISEASES AT SHRIMP FARMINGS IN THE CA MAU PENINSULA OF VIET NAM

In order to provide the basis for the application of scientific and technological advances, reorganizing shrimpfarming in sustainable and bringing high economic value to the Mekong Delta. The study surveyed the current situation of breeds, farming methods, environmental monitoring control, Vibrio sp. and the use of probiotics of shrimp farmers in the Ca Mau peninsula by interviewing 200 shrimp farmers and 20 specialized fisheries officers in Ca Mau, Soc Trang, Bac Lieu and Kien Giang provinces. The results showed that the shrimp breeds selected for farming originated from the Central and Southwest provinces. There are four popular farming methods: intensive, semi-intensive, improved extensive, and rice-shrimp. The intensive farming had the highest rates of the initial quarantine of shrimp postlarvae (74%) and Vibrio test (57%). All shrimp farmers workingon the intensive and semi-intensive farmings used probiotics. The rates of probiotic use in the improved extensive and riceshrimp farmings were lower, only 60% and 40% respectively. The results suggested that shrimp farmers working on the semi-intensive and intensive farmings paid more attention to the use of probiotics as well as the test to prevent the disease in shrimp.

Assessing changes of mangrove forest in Bac Lieu Province using multi-temporal satellite images during 1988-2018

This study is done to determine the current status of mangrove forests (mangroves) in Bac Lieu Province over the years (1988, 1998, 2013 and 2018), assess the change in mangrove area over specific periods, and at the same time determine causes of disappear and recovery processes. Landsat 5-TM, 8-OLI remote sensing image and Maximum Likelihood Classifier - MCL method were used to classify and assess the changes in the area of mangrove forests in Bac Lieu Province over the period 1988-2018. The results of the image interpretation in 1988, 1998, 2013, 2018 and the overlapping of the above maps show the area of mangroves in Bac Lieu Province has increased continuously from 1988 to 2018. During the 30-year period from 1988 to 2018, the total mangrove area in Bac Lieu increased by 1,069.4 hectares, 1.5 times higher than the original. The recovery rate of mangroves was determined to be 64.3 ha/year, 2 times higher than their disappearance rate during this period (28,7 ha/year). The main reason to the disappearance of mangroves is the conversion from mangroves to aquaculture (accounting for 91.1%), coastal erosion (accounting for 7,9%). Mangroves are restored mainly from coastal seawater surface (accounting for 46,3%), from agricultural land (27.8%), planting mangroves in abandoned shrimp ponds or planting mangroves in combination with aquaculture (accounting for 25,8%).

The Digestive Tract Morphology and Clark index of Mud Sleeper Butis koilomatodon Living in some Coastal and Estuarine areas belonging to Tra Vinh, Soc Trang, Bac Lieu and Ca Mau

This study provides new data on the characteristics of the gastrointestinal morphology and the variation of Clark index according to sexes, fish size groups, seasons and sampling sites of mud sleeper Butis koilomatodon, one of the commercially valuable gobiid species in the Mekong Delta. Analytical results of 1,227 fish samples collected monthly from April 2019 to March 2020 in Duyen Hai (Tra Vinh), Cu Lao Dung (Soc Trang), Tran De (Soc Trang), Hoa Binh (Bac Lieu), Dong Hai (Bac Lieu) and Dam Doi (Ca Mau) showed that this species had a slightly sloping mouth, the length between two jaws was relatively equal, teeth were small and grew in long lines on both jaws with the outer row having larger teeth. The length of the gut was shorter than the total length of the fish and so this species belonged to predator group. The Clark index depended on length of fish, sampling time and site but excluding season and gender. It was also effected by interactions of fish length x season; fish length x site and season x site. Conversly, the interactions of gender x season and gender x site did not impact on the Clark index. The outcomes of research will provide useful data in artificial aquaculture Butis koilomatodon.

Determinants of Retail Banking Efficiency: A Case of Vietcombank Branches in the Mekong-Delta Region

This study focused on researching the factors affecting retail banking efficiency of Vietcombank branches in the Mekong-Delta region. By collecting data from financial statements from 15 branches of VCB in the Mekong-Delta Region between 2015 and 2018, the paper applies DEA estimation to measure the effectiveness of retail banking activities and uses the Tobit regression model to identify factors affecting retail banking efficiency. The results demonstrate that the retail banking efficiency of branches averaged 52.5% during the period. The rating result shows the branches in An Giang, Can Tho, Dong Thap, Kien Giang, Long An, Phu Quoc and Tra Noc rank at the top technical efficiency. In group of medium efficiency, there are branches in Soc Trang, Tien Giang and Vinh Long. In the category of the poor efficiency are the branches in Bac Lieu, Ben Tre, Ca Mau, Chau Doc and Tra Vinh. The results also show that bank scale-related factors, capital adequacy, credit quality, time specific and region impact significantly the retail banking efficiency. The research not, only contributes to enriching the empirical research method but also is significant for the management activities in business developing strategies, improving the operational efficiency of Vietcombank in the region.

Comparison between IRI-2012, IRI-2016 models and F2 peak parameters in two stations of the EIA in Vietnam during different solar activity periods

This paper presents observations of the F2-layer critical frequency (foF2) and height (hmF2) obtained at Phu Thuy (21.03°N, 105.95°E) and Bac Lieu (9.28°N, 105.73°E) observatories in Vietnam. The data have been examined for all seasons, during high and low solar activities, and compared with the foF2 and hmF2 of the International Reference Ionosphere model (IRI-2012, IRI-2016 two options: AMTB, SHU). Phu Thuy observatory is located at the Northern Crest of the EIA and Bac Lieu in the trough of the EIA, therefore the foF2 values at Phu Thuy are higher than at Bac Lieu. The results show that the IRI-2012 model estimates well the observed foF2 at both stations during high and low solar activities. During high solar activity, models estimate well the calculated hmF2 in summer for both stations. At Phu Thuy in equinoxes AMTB reproduces the night peak better than IRI-2012 and SHU, but higher and later about 2–3 h, in winter the performance of AMTB is worst. At Bac Lieu, the IRI-2016 options reproduce the night peak and underestimates it, but IRI-2012 does not do it. The pre-noon peaks are underestimated by all the models, except IRI-2012 which overestimates the hmF2 pre-noon peaks at Bac Lieu. At Phu Thuy the pre-noon hmF2 peak is higher than the post-dusk one. At Bac Lieu the post-dusk peak is higher except in summer. During low solar activity, the IRI models estimate relatively well the shape of the calculated hmF2 at both stations. The IRI-2012 models explained better the observed foF2 (deviation of 2.5%) during solstices than during equinoxes (14.2%) for high solar activity. The IRI-2012 model explained better the observed foF2 in spring (7.8%) than in autumn (19.9%), matched better the calculated hmF2 in solstice (5.4%) than during equinoxes (11.8%). The performance of AMTB is worst at both stations for both the high and low solar activity periods except in autumn at Bac Lieu for the low solar year. IRI-2012 is best at the stations for both high and low solar activity periods, except in summer for the high solar activiy year when SHU is the best at Phu Thuy. These results can be used to improve the future IRI model.

Modelling bank erosion dependence on natural and anthropogenic factors — case study of Ganh Hao estuary, Bac Lieu - Ca Mau, Vietnam

Abstract Vietnam’s Mekong Delta is formed up with alluvial sediments and accretion over the centuries. The mixed interaction of the river — the sea have formed fertile alluvial soil, with very diverse ecosystems. During more than 300 years of exploitation, we have never had to deal with the fierce impacts of weather, climate change, along with changes from upstream leading to erosion in both estuarines and coastal areas. In recent years, there have been many tropical depressions in the area, storms create strong waves phenomena, storm surges, and changes in the upstream areas, leading to the risk of erosion tends to increase. A numerical modelling and simulation experiment is carried out to assess the impact of anthropogenic such as discharge, sediment load and natural factors such as wave, tide, sea level rise due to climate change or storms to bank erosion on estuaries and coastlines. Erosion and deposition modelling was carried out in the study area under different scenarios, pay attention to storm surges, flowrate in the estuary. The modelling results are controlled and compared with reality, allowing the evaluation of the reliability of the modelling and serving to improve the design quality of the estuarine and coastal areas protection construction.

Evaluating the potential for application of MODIS satellite data for urban air quality monitoring in Vietnam

Using satellite remote sensing data in combining with other technologies (i.e. sensor, ground-based system) for surface air quality monitoring has been considered as one of promising approaches for urban air quality management in future smart cities. This study assessed the accuracy of latest collection (Collection 6.1 - C6.1) of MODerate resolution Imaging Spectroradiometer (MODIS) satellite aerosol optical depth (AOD) retrieval by Dark Target (DT) algorithm at 3 and 10 km spatial resolutions in urban areas in Vietnam. Collocated Aqua and Terra MODIS C6.1 AOD at 550 nm were inter-compared against AOD from two AERONET stations in Vietnam, estimated throughout the satellite passes (± 1 h). Two investigated AERONET stations are Nghia Do (inland urban) and Bac Lieu (coastal urban) with the studying periods of 2010 - 2016 and 2010 - 2017, respectively. Our findings showed that the MODIS DT 3km were performed worse than the MODIS DT 10 km product in urban areas. Furthermore, all two MODIS AOD DT products showed better performance at inland urban site than coastal urban site. In general, both MODIS products were able to follow the monthly-mean AERONET AODs. The peak of aerosol loading at the investigated urban sites could be properly attributed to the combination of the monsoon effect and biomass burning activities. The mean aerosol loading of rainy season appeared to be lowest in the year, which could be attributed to the fact that the frequent rain washes out the dust in the atmosphere.

INTER-COMPARISON BETWEEN MODIS SATELLITE-BASED AND AERONET GROUND-BASED AEROSOL OPTICAL DEPTH PRODUCTS IN VIETNAM

Although a number of studies have extensively inter-compared the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite-based aerosol optical depth (AOD) with the Aerosol Robotic Network (AERONET) ground-based AOD on both global and regional scales, almost no similar studies have been conducted for Vietnam - a humid subtropical climate region. For the first time, inter-comparison between the MODIS Terra and Aqua Collection 6.1 (C6.1) Dark Target (DT) 10 km, Deep Blue (DB) 10 km, and merged DT-DB 10 km with the AERONET AODs has been performed in different areas with different surface types and different climatic characteristics in Vietnam. Three investigated AERONET stations are Nghia Do (urban), Son La (mountainous rural), and Bac Lieu (coastal urban) with the studying periods of 2010 - 2016, 2012 - 2017, and 2010 - 2017, respectively. Our findings showed the better performances of DB algorithm than those of DT and DT-DB products in the urban area. Additionally, all MODIS AOD algorithm performed worse over the coastal area compared to those in the non-coastal areas. Generally, the ability of all the MODIS AODs to catch up the monthly-mean AERONET AODs has been expressed in this study.

The use of machine learning to predict acute hepatopancreatic necrosis disease (AHPND) in shrimp farmed on the east coast of the Mekong Delta of Vietnam

Predicting the outbreak of disease is essential when managing shrimp farms. Acute hepatopancreatic necrosis disease (AHPND) caused by Vibrio parahaemolyticus is a serious disease in shrimp. It is essential that shrimp farmers on the east coast of the Mekong Delta detect the disease as early as possible, because the mortality rate can reach 100%. Here, we used machine learning to predict AHPND development based on data collected since 2010 from shrimp farms in Tra Vinh, Ben Tre, Bac Lieu, and Ca Mau provinces. We initially hypothesized that the dependent variable, AHPND, was affected by 31 independent variables, but ultimately used 15 key variables to train the models. Logistic regression, artificial neural network, decision tree, and K-nearest neighbor analyses were performed, and the accuracy of the predictions was evaluated using hold-out and cross-validation tests. Logistic regression, as the most stable algorithm, was thus used to predict AHPND outbreaks in shrimp farms.

Economic evaluation for improving productivity of brine shrimp Artemia franciscana culture in the Mekong Delta, Vietnam

The Artemia culture industry in the Mekong Delta plays an important role in providing high quality and quantity of dormant cyst for global aquaculture. Nevertheless, varying geographic location and production scale may affect the productivity and economic performance of the industry. This study presents an economic analysis by considering the interaction effect of geographic location and production scale for improving productivity of Artemia culture in the Mekong Delta. The data were surveyed from 57 farms in Vinh Chau and 37 farms in Bac Lieu. According to multivariate statistical analysis, the profitabilities of Artemia farms were significantly influenced by geographic location and its interaction with production scale (p < .001). Farms in Vinh Chau obtained higher economic performance compared to those in Bac Lieu, with the greatest profitability denoted for small-scale farms in Vinh Chau. To improve farm productivity, beside maintaining optimal stocking densities, moderate increases of organic fertilizer, feed and chemical inputs are recommended to supply Artemia with more nutrients and create better water environment for the optimal development and reproduction of Artemia. Additionally, a periodic harvest of Artemia biomass (adult Artemia) is required to minimize food and space competition and provide more incomes to farmers. In terms of supportive strategies, the government in Bac Lieu is proposed to have more investment policies for farm land and strengthen the establishments and activities of local cooperatives for further technical and financial assistance in Artemia culture.

Sustainable development for water resources of Litopenaeus Vannamei prawn farming in Bac Lieu province

Sustainable development for water resources of Litopenaeus Vannamei prawn farming in Bac Lieu province

Data envelopment analysis for production efficiency improvement: An empirical application on brine shrimp Artemia franciscana culture in the Mekong Delta, Vietnam

Artemia culture in the Mekong Delta, Vietnam, is becoming more and more important to satisfy the global demands of cyst production. Nevertheless, Artemia cyst productivity in the Mekong Delta has been fluctuating largely due to not only technical inefficiencies and external factors but also farms’ characteristics. This study employed a data envelopment analysis to evaluate the production efficiencies in correlation with biological and cost inputs of Artemia culture in Vinh Chau and Bac Lieu located in the Mekong Delta. The key factors affecting technical efficiency (TE) were determined using ordinary least squares regression model. The empirical results indicated that production efficiencies of farms in Vinh Chau and Bac Lieu were similar with metatechnology ratios of 0.97 and 0.96 respectively. About 62.8% of surveyed farms were operating in technically inefficient circumstances. Farmers’ experience, educational level and culture technique training participation had positive effects on TE, while climate effects and water problems have been proved to have negative effects on TE. To improve production efficiency, inefficient farms are suggested to have moderately increasing combinations of organic fertilizer, chemical and feed. The use of probiotics should be reduced as it increases production cost and affects TE. Notably, a collaboration of scientists and feed processing companies is recommended to produce a specific formulated feed for Artemia in commercial scales. This study also proposes adaptive policies for local governments and cooperatives to assist coastal famers in the Mekong Delta overcome technical inefficiencies, improve cyst productivity and obtain economic sustainability in Artemia culture.