Small-scale marine fisheries policy in Vietnam

Vietnam's marine fisheries are considered to be small scale and are concentrated in coastal near-shore waters. This has resulted in heavy pressure on near-shore fisheries resources. Near-shore fisheries are considered by fishers and the government to be over-exploited, causing hardship for many coastal communities. This paper reviews and analyzes changes in policy towards small-scale fisheries in Vietnam over the last two decades. The primary issues facing the small-scale fisheries in Vietnam are to restructure the near-shore fisheries and to address over-capacity. Recommended actions include improved fisheries statistics, resources for provincial fisheries staff, and a coordinated and integrated approach involving a mixed strategy of resource management; resource restoration; economic and community development; and new governance arrangements.     

Petroleum composition in the Cuu Long Basin (Mekong Basin) offshore southern Vietnam

The Cuu Long Basin (Mekong Basin) is a rift basin off southern Vietnam, and the most important petroleum producing basin in the country. However, information on petroleum type and characteristics has hitherto been largely unavailable to the public. This paper presents petroleum geochemical data on nine oil samples from four different producing fields in the Cuu Long Basin: the Dragon (Rong), Black Lion (Sutu-Den), Sunrise (Rang ?ong) and White Tiger (Bach Ho) Fields. The oils are highly paraffinic with bimodal normal alkane distributions and show moderate pristane to phytane ratios and a conspicuous hyperbolic decrease in abundance with increasing carbon number of hopane homologues from C₃₀ to C₃₅. The TPP-index of Holba et al. (Holba, A.G., Dzou, L.I., Wood, G.D., Ellis, L., Adam, P., Schaeffer, P., Albrecht, P., Greene, T., Hughes, W.B., 2003. Application of tetracyclic polyprenoids as indicators of input from fresh–brackish water environments. Organic Geochemistry 34, 441–469) is equal to 1 in all samples which in combination with tricyclic triperpane T26/T25 ratios >1 and the n-alkane and hopane distributions mentioned above provide a strong indication of an origin from lacustrine source rocks. This is supported by the absence of marine C₃₀ desmethyl steranes (i.e. 24-n-propylcholestanes) and marine diatom-derived norcholestanes. Based on the overall biological marker distributions, the lakes probably belonged to the overfilled or balanced-fill types defined by Bohacs et al. (Bohacs, K.M., Carroll, A.R., Neal, J.E., Mankiewicz, P.J., 2000. Lake-basin type, source potential, and hydrocarbon character. An integrated sequence-stratigraphic–geochemical framework. AAPG Studies in Geology 46, 3–34). The oils were generated from source rocks at early- to mid-oil-window maturity, presumably Oligocene lacustrine shales that are present in the syn-rift succession. Oils from individual fields may, however, be distinguished by a combination of biological marker parameters, such as the oleanane index, the gammacerane index, the relative abundance of tricyclic terpanes, the proportions of diasteranes and 28-norspergulane, complemented by other parameters. The oils of the Cuu Long Basin show an overall similarity to the B-10 oil from the Song Hong Basin off northern Vietnam, but are markedly different from the seepage oils known from Dam Thi Nai on the coast of central Vietnam.     

Effect of open gap in coastal forest on tsunami run-up—investigations by experiment and numerical simulation

The objective of this study is to investigate the effects of an open gap, such as a road, in a coastal forest on tsunami run-up. A numerical model based on two-dimensional nonlinear long-wave equations was developed to account for the effects of drag and turbulence induced shear forces due to the presence of vegetation. Experiments were conducted on a forest simulated with vertical cylinders by changing the gap width. The numerical model was validated in good agreement with the experimental results. The numerical model was then applied to a wide forest of Pandanus odoratissimus, a tree species that is a dominant coastal vegetation on a sand dune in South and Southeast Asia. The effect of vertical stand characteristics of P. odoratissimus with aerial roots was considered on the drag resistance. A straight open gap perpendicular to the shoreline was used to investigate the effect of gap width. As the gap width increases, the flow velocity at the end of the open gap first increases, reaches a maximum, and then decreases, while the run-up height increases monotonously. The maximum velocity in the present condition is 1.7 times the maximum velocity without a coastal forest. The effects of different gap arrangements in the forest on tsunami run-up were also investigated in this paper. The flow velocity at the end of an open gap can be reduced by a staggered arrangement.     

Meiobenthos in estuary part of ha long bay (gulf of tonkin, south china sea, vietnam)

The distribution of the taxonomical composition and the density of meiobenthos depending on some factors of environment has been studied in bottom sediments of the northern estuary part of Ha Long Bay (Cua Luc estuary). The basic factor of influence on meiobenthic community structure was the granulometric composition of sediment. The greatest taxonomic diversity is noted in the silted sands, lowest — in the silty sediments. The density of meiobenthic community was higher in the silty sediments. Slightly expressed correlation between the density of nematodes and the percentage of silty particles in the sediments is detected (Spearman rank correlation coefficient was 0.49±0.21, p=0.035). The nematodes were dominant at all stations. In total, representatives of 66 species of nematodes belonging to 17 families and 52 genera were identified.     

A history of breaking laws—Social dynamics of non-compliance in Vietnamese marine fisheries

Whether or not fishers comply with regulation depends on the economic and social context in which they operate their vessels. This is how conventional theory explains the phenomenon of non-compliance. It treats state–community interaction processes not as direct causes for non-compliance but rather as background conditions shaping individual fishers’ perception and decisions for action. This paper argues that conventional theory fails to include the dynamics of tempo-relational processes between state and communities, which explains collective patterns of non-compliance in fisheries. The paper addresses this hiatus in the literature, using a process-sociological approach to analyse non-compliance in Vietnamese marine fisheries. The analysis highlights that Vietnamese marine fisheries are mainly regulated through informal networks of trust and mistrust, which function through their interplay with the highly centralised and formalised Vietnamese state. Based on this assessment, the paper concludes that outcomes of processes of the dynamic social interplay between state and communities are semi-dependent on individual perception and action, and as such have a causal effect of their own on patterns of non-compliance in fisheries.     

Geoacoustic Inversions of Horizontal and Vertical Line Array Acoustic Data From a Surface Ship Source of Opportunity

The application of an inversion methodology produces the first demonstration of a simultaneous solution for geoacoustic and source track parameters from acoustic data collected in a shallow-water, sandy sediment environment. Inversion solutions from data collected in the 2006 Shallow Water Experiment (SW06) are extracted from noise measurements of a surface ship source on an L-array. The methodology includes a screening algorithm to determine a set of frequencies for the inversion data. In addition, the methodology assesses the accuracy of the inversion solution and incorporates an estimation of parameter value uncertainties. The solution from the inversion of the horizontal component of the L-array data from the surface ship source before its closest point of approach (CPA) is used to construct modeled propagation loss for comparison with observed received level (RL) structure as the source departs from CPA. Inversion of the data from a single element in the vertical component of the L-array produces a solution that agrees with the solution obtained from the inversion of horizontal subaperture data. Also, modeled transmission loss (TL) structure obtained from the single-element inversion solution reproduces the depth dependence of the RL structure observed at other elements of the vertical component of the L-array.      

Slow quasigeostrophic unstable modes of a lens vortex in a continuously stratified flow

This work addresses the linear dynamics underlying the formation of density interfaces at the periphery of energetic vortices, well outside the vortex core, both in the radial and axial directions. We compute numerically the unstable modes of an anticyclonic Gaussian vortex lens in a continuously stratified rotating fluid. The most unstable mode is a slow mode, associated with a critical layer instability located at the vortex periphery. Although the most unstable disturbance has a characteristic vertical scale which is comparable to the vortex height, interestingly, the critical levels of the successively fastest growing modes are closely spaced at intervals along the axial direction that are much smaller than the vortex height.     

“豫灵人”发现区的地貌

本文从地貌基本特征、地貌形态结构和地貌形成演变等三方面,论述了豫灵人发现区的地貌。     

“豫灵人”发现区第四系与古人类相关问题分析

本文通过对“豫灵人”发现区地壳发展历史和第四系成因类型的分析,提出了“豫灵人”发现区古人化石所在地的中更新统上部地层是本区继续寻找发现古人化石和旧石器的重要地区与地层之一。     

用地面气温特征向量场探讨北半球七十年代的气候特征

本文利用自然正交展开的分析方法,对10°S—80°N地区1968年12月—1978年11月历年逐月的地面温度距平场进行了分解.从分析中得到七十年代地面气温场变化的主要特征是:温度变化趋势是以多振动为主;夏季平均变化是偏冷的,冬季是偏暖的.再者是东半球的变化大于西半球,极区与中高纬的变化是反相的.通过分析温度变化的特征,进一步探讨了七十年代异常气候频繁出现的原因,表明气候异常主要是由于中高纬地区温度梯度变化加强,致使大气斜压性产生剧烈的变化而造成的.