Environmental impact assessment of the pangasius sector in the Mekong Delta

In the past seven years the export of white pangasius fillets grew fast. The culture method shifted to intensive production of striped catfish (Ca Tra) in deep ponds because this is more efficient than the pen and cage culture of Ca Basa. Today, striped catfish comprises more than 90 % of the culture. The increased production was achieved by producers investing in large ponds. The market chain is gearing towards vertical integration. Most farms keep fish at relatively high densities of 15 to 25 fish/m3 in ponds having a depth of up to 4m, and are advised to exchange daily 20 to 40% of the water. The sustainability of the sector is threatened due to the increased environmental pressure, and hampered by the growing cost of inputs and reduced farm-gate prices of the fish. The Environmental Impact Assessment (EIA) intends to identify measures for preventing or mitigating the environmental impacts of catfish culture in the Mekong Delta. The EIA was a seven-step process during which we interacted twice with part of the main stakeholders. To build trust among the stakeholders from the sector, we conducted the scoping and goal setting with them

Changes in mangrove vegetation area and character in a war and land use change affected region of Vietnam (Mui Ca Mau) over six decades

Aerial photographs and satellite images have been used to determine land cover changes during the period 1953 to 2011 in the Mui Ca Mau, Vietnam, especially in relation to changes in the mangrove area. The mangrove area declined drastically from approximately 71,345 ha in 1953 to 33,083 ha in 1992, then rose to 46,712 ha in 2011. Loss due to herbicide attacks during the Vietnam War, overexploitation, and conversion into agriculture and aquaculture encouraged by land management policies are being partially counteracted by natural regeneration and replanting, especially a gradual increase in plantations as part of integrated mangrove-shrimp farming systems. The nature of the mangrove vegetation has markedly been transformed over this period. The results are valuable for management planning to understand and improve the contribution of mangrove forests to the provision of ecosystem services and resources, local livelihood and global interest

Caretaker mental health and family environment factors are associated with adolescent psychiatric problems in a Vietnamese sample

Little is known about risk factors for adolescent mental health in Vietnam. The present study investigated the relationship between caretaker mental health and adolescent mental health in a cross-sectional Vietnamese sample. Primary caretakers completed measures of their own mental distress and general health status using the Self-Reporting Questionnaire-20 (SRQ-20) as well as reports of adolescent mental health using the parent version of the Strengths and Difficulties Questionnaire (SDQ). Multivariate regression models were used to examine the relationships between the caretaker and adolescent health variables. The demographic factors of age, sex, ethnicity, religious affiliation, and household wealth status demonstrated significant relationships with SDQ subscale scores. Caretaker mental health was positively associated with adolescent mental health, and this association remained significant even after accounting for other relevant demographic variables and caretaker general health status. Understanding correlates of adolescent mental health difficulties may help identify youth and families at risk for developing psychiatric problems and inform mental health interventions in Vietnam

The Lensed Lyman-Alpha MUSE Arcs Sample (LLAMAS)

Aims. We present the Lensed Lyman-Alpha MUSE Arcs Sample (LLAMAS) selected from MUSE and HST observations of 17 lensing clusters. The sample consists of 603 continuum-faint (−23 < MUV < −14) lensed Lyman-α emitters (producing 959 images) with secure spectroscopic redshifts between 2.9 and 6.7. Combining the power of cluster magnification with 3D spectroscopic observations, we were able to reveal the resolved morphological properties of 268 Lyman-α emitters. Methods. We used a forward-modeling approach to model both Lyman-α and rest-frame UV continuum emission profiles in the source plane and measure spatial extent, ellipticity, and spatial offsets between UV and Lyman-α emission. Results. We find a significant correlation between UV continuum and Lyman-α spatial extent. Our characterization of the Lyman-α halos indicates that the halo size is linked to the physical properties of the host galaxy (SFR, Lyman-α equivalent width, Lyman-α line FWHM). We find that 48% of Lyman-α halos are best fit by an elliptical emission distribution with a median axis ratio of q = 0.48. We observe that 60% of galaxies detected both in UV and Lyman-α emission show a significant spatial offset (ΔLyα − UV). We measure a median offset of ΔLyα − UV = 0.58 ± 0.14 kpc for the entire sample. By comparing the spatial offset values with the size of the UV component, we show that 40% of the offsets could be due to star-forming sub-structures in the UV component, while the larger offsets (60%) are more likely due to greater-distance processes such as scattering effects inside the circumgalactic medium or emission from faint satellites or merging galaxies. Comparisons with a zoom-in radiative hydrodynamics simulation of a typical Lyman-α emitting galaxy show a very good agreement with LLAMAS galaxies and indicate that bright star-formation clumps and satellite galaxies could produce a similar spatial offset distribution

Growth performance of Dipterocarpus alatus and Hopea odorata in degraded secondary forest land in Southern Vietnam

The two dipterocarp species, Dipterocarpus alatus and Hopea odorata, have been widely planted in degraded forest land in Southern Vietnam in the last decades. However, study on growth characteristics of these species and their associated factors is still limited. Therefore, the present study aimed to examine growth performance in different stand densities, and classify tree quality in 28-year old D. alatus and H. odorata plantations. Our results of analysis of covariance (ANCOVA) indicated that in pure stand aged 28 years, D. alatus outperformed H. odorata in tree growth, biomass and volume. In addition, except for four growth variables including tree height at the first branch (Hb), crown length (CL), crown ratio (CR) and linear crown index (LCI), the remaining variables were negatively affected by stand density. We observed that medium quality trees occupied the greatest proportion in both D. alatus (47%; n = 425) and H. od- orata (50%; n = 400). Except for CR and LCI, the class of good quality trees had the greatest values in the remaining examined growth variables. In linear discriminant analysis (LDA) model, the classification accuracy of testing set was relatively high in both D. alatus (85%) and H. odorata (91%). The most impor- tant variables for tree quality classification in D. alatus were crown diameter (CD) and diameter at breast height (DBH). Meanwhile, the most important variables in H. odorata were CD and tree height (H). These obtained results suggest that controlling crown size is important for shaping individual tree quality. Our data evidenced that D. alatus and H. odorata planted in Southern Vietnam with density equal or less than 500 trees per ha could yield high proportion of good and medium quality trees

Post-typhoon prevalence of post-traumatic stress disorder, major depressive disorder, panic disorder, and generalized anxiety disorder in a Vietnamese sample

In 2006, typhoon Xangsane disrupted a multiagency health needs study of 4,982 individuals in Vietnam. Following this disaster, 798 of the original participants were reinterviewed to determine prevalence and risk factors associated with posttraumatic stress disorder (PTSD), major depressive disorder (MDD), panic disorder (PD), and generalized anxiety disorder (GAD). Posttyphoon prevalences were PTSD 2.6%, MDD 5.9%, PD 9.3%, and GAD 2.2%. Of those meeting criteria for a disorder, 70% reported only one disorder, 15% had two, 14% had three, and 1% met criteria for all four disorders. Risk factors for posttyphoon psychopathology differed among disorders, but generally were related to high typhoon exposure, prior trauma exposure, and in contrast to Western populations, higher age, but not gender

Antimicrobial susceptibility pattern of <i>Edwardsiella ictaluri</i> isolates from natural outbreaks of bacillary necrosis of <i>Pangasianodon hypophthalmus</i> in Vietnam

The purpose of this study was to assess the in vitro susceptibility of 64 Vietnamese isolates of Edwardsiella ictaluri, the causal agent of the infectious disease Bacillus Necrosis Pangasius in Pangasianodon hypophthalmus, using the agar dilution technique. All isolates originated from different farms and were collected between 2002 and 2005. None of the isolates displayed acquired resistance to amoxicillin, amoxicillin-clavulanic acid, chloramphenicol, florfenicol, gentamicin, kanamycin, neomycin, and nitrofurantoin. Acquired resistance to streptomycin was detected in 83%, to oxytetracycline in 81%, and to trimethoprim in 71% of the isolates, as indicated by a bimodal distribution of the minimal inhibitory concentrations (MICs) of these antimicrobials. The MICs of enrofloxacin displayed a monomodal distribution with tailing toward the higher MIC values, possibly indicating reduced susceptibility of a minority of isolates (3 out of the 64). For the quinolone antimicrobial agents flumequin and oxolinic acid, acquired resistance was encountered in 8% and 6% of the strains, respectively. All strains were intrinsically resistant to the polypeptide antimicrobial agent colistin. Seventy-three percent of the isolates were shown to have acquired resistance to at least three antimicrobial agents. The results of this study emphasize the strict need to control both the prophylactic and curative use of antimicrobial agents in Vietnamese aquaculture