Small-scale marine fisheries policy in Vietnam   总被引：1，自引：0，他引：1  

Robert Pomeroy  Kim Anh Thi Nguyen  Ha Xuan Thong 《Marine Policy》2009

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.  相似文献   

High-resolution record of tectonic and sedimentary processes in growth strata     

Stphane Pochat  Sbastien Castelltort  Gaël Choblet  Jean Van Den Driessche 《Marine and Petroleum Geology》2009,26(8):1350-1364

Growth strata are used to determine the kinematics of synsedimentary structures such as faults. Classical methods of analysis such as thickness versus throw plot consider that the available space created by fault slip in the hanging wall of faults is instantaneously filled up by sediments. This has lead many previous works to identify a cyclic activity for growth faults. Here we perform a careful analysis of the variation of strata thicknesses on each side of a very well documented normal growth fault in the Niger delta. We show that these thickness variations are induced by the alternation of sedimentary processes during continuous fault slip. Suspended-load processes induce either uniform or slightly variable thickness of a large majority of mudstone layers. Bedload processes result in a preferential thickening of sand layers in the hanging wall. These high quality data thus provide strong grounds for doubting the polycyclic growth diagnosed for some faults at the scale of sedimentary cycles and supports the notion that fault displacement rates can be very well behaved. Our study emphasizes the important conclusion that stable fault growth, and related displacement rates, can appear to be punctuated when viewed at the scale of sedimentary cycles. It follows that care should be taken when attempting to derive displacement rates on temporal scales equivalent to those of alternating sedimentological cycles.  相似文献   

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

Jørgen A. Bojesen-Koefoed  H. Peter Nytoft  Nguyen Thi Dau 《Marine and Petroleum Geology》2009

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.  相似文献   

GPS���ܵ��㶨λ��Ӱ������ʱ������ؼ���ʩ����   总被引：1，自引：0，他引：1  

郑作亚  党亚民  卢秀山  郭金运  阳凡林 《大地测量与地球动力学》2009,29(5):107-111

??GPS??????λ?????????У?????????????????估???????λ??????????????????????????????????????????λ????????????λ?????????????????????????????????????????????????????????伸?ι?????????????????????????????Щ???????????????????????????????????????????????????????  相似文献   

Instantaneous Shorelines as an Intermediate for Island Shoreline Mapping based on Aerial/Satellite Stereo Images     

Yamin Dang  Xinghua Zhou  Jun Xu  Shuqiang Xue 《Marine Geodesy》2018,41(3):219-229

Island shoreline mapping based on field measurements by collecting visually discernible features is costly and even unrealistic to be implemented in practice because of the nonuniqueness, fuzziness, and ambiguity of shoreline features. The MHHW (the mean higher high water) shoreline, i.e., the intersection of the coastal profile with the MHHW, is recommended to be chosen as a significant shoreline indicator of an island. An approach for mapping the MHHW shoreline using the aerial/satellite stereo images is proposed. In the proposed procedure, first, the height difference between the instantaneous shoreline and the MHHW shoreline is calculated by the ocean tide model; then the orthometric/normal height of the instantaneous shoreline is determined from the stereo images; last, the instantaneous shoreline is used as an intermediate for determination of the height of the MHHW shoreline. The proposed procedure is applied to the MiaoZiHu Island located in the East China Sea. Preliminary experimental result shows that in ideal cases, the horizontal positional accuracy of the extracted shoreline can reach 0.2 m from aerial images of 0.1 m resolution.  相似文献   

Why chromatic imaging matters     

Joel Sanchez-Bermudez  Florentin Millour  Fabien Baron  Roy van Boekel  Laurent Bourgès  Gilles Duvert  Paulo J. V. Garcia  Nuno Gomes  Karl-Heinz Hofmann  Thomas Henning  Jacob W. Isbell  Bruno Lopez  Alexis Matter  J-Uwe Pott  Dieter Schertl  Eric Thiébaut  Gerd Weigelt  John Young 《Experimental Astronomy》2018,46(3):457-473

During the last two decades, the first generation of beam combiners at the Very Large Telescope Interferometer has proved the importance of optical interferometry for high-angular resolution astrophysical studies in the near- and mid-infrared. With the advent of 4-beam combiners at the VLTI, the u ? v coverage per pointing increases significantly, providing an opportunity to use reconstructed images as powerful scientific tools. Therefore, interferometric imaging is already a key feature of the new generation of VLTI instruments, as well as for other interferometric facilities like CHARA and JWST. It is thus imperative to account for the current image reconstruction capabilities and their expected evolutions in the coming years. Here, we present a general overview of the current situation of optical interferometric image reconstruction with a focus on new wavelength-dependent information, highlighting its main advantages and limitations. As an Appendix we include several cookbooks describing the usage and installation of several state-of-the art image reconstruction packages. To illustrate the current capabilities of the software available to the community, we recovered chromatic images, from simulated MATISSE data, using the MCMC software SQUEEZE. With these images, we aim at showing the importance of selecting good regularization functions and their impact on the reconstruction.  相似文献   

Coral assemblages and reef growth in the Commonwealth of the Northern Mariana Islands (Western Pacific Ocean)     

Peter Houk  Robert Van Woesik 《Marine Ecology》2010,31(2):318-329

Reef development varies considerably around the high, raised‐limestone islands of the Commonwealth of the Northern Mariana Islands (CNMI). Here we examine the modern assemblages at 30 sites for coral composition, colony density, colony size, and fidelity. We defined four reef types and hypothesize the presence of environmentally driven ecological stasis, whereby the environment continuously selects for coral species membership, defines colony sizes, and over time creates the noted reef types. Our results show that constructional spur‐and‐groove reefs supported significantly larger coral‐colony sizes and higher coral species richness compared with high‐relief interstitial framework, low‐relief incipient, and non‐constructional coral assemblages. Non‐constructional reefs supported much smaller coral colony sizes, despite similar population densities, and were consistently found in association with high wave exposure. The distinct coral assemblages found on interstitial framework and low‐relief incipient reefs were not affiliated with any wave exposure regime, but were located adjacent to large watersheds and on islands with unique geological history. These assemblages were nested within the spur‐and‐groove species pool. Overall, modern coral cover was well predicted by bathymetric slope and watershed size, while species richness was additively influenced by two proxies of pollution, suggesting the latter is better suited for establishing management targets. In contrast with previous studies that suggested modern assemblages were biologically controlled in the CNMI, we show reef assemblages and reef development are highly influenced by long‐term environmental forcing.  相似文献   

Dissolved organic nitrogen dynamics in the North Sea: A time series analysis (1995–2005)     

T. Van Engeland  K. Soetaert  A. Knuijt  R.W.P.M. Laane  J.J. Middelburg 《Estuarine, Coastal and Shelf Science》2010

Dissolved organic nitrogen (DON) dynamics in the North Sea was explored by means of long-term time series of nitrogen parameters from the Dutch national monitoring program. Generally, the data quality was good with little missing data points. Different imputation methods were used to verify the robustness of the patterns against these missing data. No long-term trends in DON concentrations were found over the sampling period (1995–2005). Inter-annual variability in the different time series showed both common and station-specific behavior. The stations could be divided into two regions, based on absolute concentrations and the dominant times scales of variability. Average DON concentrations were 11 μmol l⁻¹ in the coastal region and 5 μmol l⁻¹ in the open sea. Organic fractions of total dissolved nitrogen (TDN) averaged 38 and 71% in the coastal zone and open sea, respectively, but increased over time due to decreasing dissolved inorganic nitrogen (DIN) concentrations. In both regions intra-annual variability dominated over inter-annual variability, but DON variation in the open sea was markedly shifted towards shorter time scales relative to coastal stations. In the coastal zone a consistent seasonal DON cycle existed with high values in spring–summer and low values in autumn–winter. In the open sea seasonality was weak. A marked shift in the seasonality was found at the Dogger Bank, with DON accumulation towards summer and low values in winter prior to 1999, and accumulation in spring and decline throughout summer after 1999. This study clearly shows that DON is a dynamic actor in the North Sea and should be monitored systematically to enable us to understand fully the functioning of this ecosystem.  相似文献   

Marine protected areas—substantiating their worth     

H. Glenn  P. Wattage  S. Mardle  T. Van Rensburg  A. Grehan  N. Foley 《Marine Policy》2010

With the UK Marine Bill promoting the creation of a network of marine protected areas and similar commitments in other countries there is a need for tools to assist in their design and management. Although physical science often drives designation, the implementation of marine protected areas also encompasses political and socio-economic issues. This paper focuses on one tool in the armoury of decision-makers: choice experiments. It illustrates its application to the quantification of aspects of socio-economic value not readily incorporated into the evaluation of the costs and benefits of marine protected areas utilising cold-water deep coral reefs off the Republic of Ireland.  相似文献   

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

Wiebren J. Boonstra  Nguyen Bach Dang 《Marine Policy》2010

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.  相似文献