GOVERNING THE ENVIRONMENTAL AND SOCIAL DIMENSIONS OF PANGASIUS PRODUCTION IN VIETNAM: A REVIEW∗

The Vietnamese government's policies for an export-led economy have supported the rapid growth of Pangasius production but have had limited success in mitigating the environmental and social impacts stemming from unplanned and ad hoc expansion. Recognising the poor performance of state regulation the industry and government have turned to private or market-based environmental and social standards for Pangasius production. The success of these private governance arrangements is dependent on the capacity of producers to comply with standards within their wider environmental, social, cultural and economic context. This paper reviews current concerns over the sustainability of Pangasius production and draws attention to the challenges private governance initiatives face in steering towards sustainable production.     

The influence of the extensional viscosity of very low concentrations of high molecular mass water-soluble polymers on atomisation and droplet impact

BACKGROUND: Water-soluble polymers are increasingly added to herbicide and pesticide formulations at very low concentrations (100-1000 mg L(-1)) in order to control the spray characteristics, notably to reduce spray drift and influence droplet bounce. The incorporation of polymeric adjuvants improves the efficacy of the spray solutions, thus enabling crop growers to maximise the performance of agrochemical sprays at lower dose rates of active ingredient. It is important to establish a fundamental understanding of how polymers influence the processes involved in droplet deposition.RESULTS: The shear and extensional viscosities of a series of high molecular mass (M(w)) poly(acrylamides) (M(w) approximately 10(6)-10(7)) have been determined at very low concentrations (100-1000 mg L(-1)). The polymer solutions demonstrated typical shear thinning characteristics under shear, and strain hardening behaviour under extension above a critical strain rate. The presence of the polymers was shown to increase the size of droplets produced in atomisation using an agricultural spray nozzle, as measured by laser diffraction. This was attributed to the increase in the extensional viscosity at the strain rates generated under pressure in the spray nozzle and was a function of both polymer concentration and M(w). In addition, the presence of polymer was found to have a significant influence on droplet bounce.CONCLUSIONS: The presence of very low concentrations of high molecular mass poly(acrylamides) significantly influences the size of droplets formed on atomisation and subsequent bounce characteristics. Large extensional viscosities generated above a critical strain rate are responsible for both processes.     

赣南脐橙溃疡病菌菌系分化初步研究

从赣南6县市分离得到22株脐橙溃疡病菌并对其进行25项生理生化试验,结果表明,在所测试的16项生理特征中有8项(果糖、乳糖、麦芽糖、葡萄糖、柠檬酸盐、醋酸盐、耐盐性(1%～3%)和pH(5.0～8.0),反应结果相同,而在埘蔗糖、木糖、肌醇、山梨醇、甘露醇等碳源利用上存在差异显著;在9项生化试验项目中除硝酸盐还原都为阳...     

Declining birds in Australian agricultural landscapes may benefit from aspects of the European agri-environment model

Temperate Australia’s wheat/sheep zone and much of Western Europe have both experienced dramatic declines in native bird populations associated with agricultural landscapes. We compare recent conservation strategies on private land in the context of each region’s historical agricultural development and the ecology of its bird fauna. Specifically, we consider which aspects of the conservation instruments and practices employed in European agricultural landscapes might be used to augment and inform approaches to private-land biodiversity conservation in Australia. Australian biodiversity conservation activities have focussed predominantly on remnant native vegetation and rarely target the agricultural matrix (i.e. land that is primarily used for agricultural production). However, declining species include those that not only primarily inhabit woodland, but also species for which components of the agricultural matrix are important, or even their main, habitat. In contrast, in Europe a range of conservation activities undertaken through agri-environment schemes focus explicitly on the management of the agricultural matrix. Whilst the different approaches to conservation on private land in Australia and Europe reflect the two continents’ different ecologies, land-use histories and political economies of agriculture, there are a number of parallels between bird population declines in the two regions, and an opportunity may exist to incorporate some of the successful aspects of the European agri-environment approach into emerging stewardship schemes in Australia. We suggest that the long-term nature of European agri-environment agreements, the principle of landholder payments more commensurate with reduced production opportunity and management actions specifically targeted at the agricultural matrix, are features of the European scheme that could benefit both woodland- and matrix-inhabiting bird species in Australian agricultural landscapes.     

Multivariate global sensitivity analysis for dynamic crop models

Dynamic crop models are frequently used in ecology, agronomy and environmental sciences for simulating crop and environmental variables at a discrete time step. They often include a large number of parameters whose values are uncertain, and it is often impossible to estimate all these parameters accurately. A common practice consists in selecting a subset of parameters by global sensitivity analysis, estimating the selected parameters from data, and setting the others to some nominal values. For a discrete-time model, global sensitivity analyses can be applied sequentially at each simulation date. In the case of dynamic crop models, simulations are usually computed at a daily time step and the sequential implementation of global sensitivity analysis at each simulation date can result in several hundreds of sensitivity indices, with one index per parameter per simulation date. It is not easy to identify the most important parameters based on such a large number of values. In this paper, an alternative method called multivariate global sensitivity analysis was investigated. More precisely, the purposes of this paper are (i) to compare the sensitivity indices and associated parameter rankings computed by the sequential and the multivariate global sensitivity analyses, (ii) to assess the value of multivariate sensitivity analysis for selecting the model parameters to estimate from data. Sequential and multivariate sensitivity analyses were compared by using two dynamic models: a model simulating wheat biomass named WWDM and a model simulating N₂O gaseous emission in crop fields named CERES-EGC. N₂O measurements collected in several experimental plots were used to evaluate how parameter selection based on multivariate sensitivity analysis can improve the CERES-EGC predictions.The results showed that sequential and multivariate sensitivity analyses provide modellers with different types of information for models which exhibit a high variability of sensitivity index values over time. Conversely, when the parameter influence is quite constant over time, the two methods give more similar results. The results also showed that the estimation of the parameters with the highest sensitivity indices led to a strong reduction of the prediction errors of the model CERES-EGC.     

A comparative review of fisheries management experiences in the European Union and in other countries worldwide: Iceland,Australia, and New Zealand

This study compares the details and performance of fisheries management between the EU and a selection of other countries worldwide: Iceland, New Zealand, and Australia, which are considered in many respects to be among the most advanced in the world in fisheries management. Fisheries management in the EU, Iceland, Australia, and New Zealand has developed following different paths, despite being based on similar instruments and principles. Iceland, Australia, and New Zealand have been at the forefront of developing management practices such as stakeholder involvement, legally binding management targets (Australia, New Zealand), individual transferable quotas, and discard bans (Iceland, New Zealand). The EU has since the beginning of the 21st century taken significant steps to better involve stakeholders and establish quantitative targets through management plans, and a landing obligation is gradually being implemented from 2015 onward. The management of domestic fisheries resources in Australia, New Zealand, and Iceland has, overall, performed better than in the EU, in terms of conservation and economic efficiency. It should, however, be stressed that, compared to Australia, New Zealand, and Iceland, (i) initial over‐capacity was more of an issue in the EU when management measures became legally binding and also that (ii) EU has been progressive in developing common enforcement standards, on stocks shared by sovereign nations. The situation of EU fisheries has substantially improved over the period 2004–2013 in the northeast Atlantic, with fishery status getting close to that in the other jurisdictions, but the lack of recovery for Mediterranean fish stocks remains a concern.     

A collective navigation hypothesis for homeward migration in anadromous salmonids

Anadromous salmon (genera Oncorhynchus and Salmo) spend much of their lives feeding in productive northern oceans and then return home to natal sites for reproduction with remarkable accuracy. The mechanisms used for navigation by individuals during migrations are thought to include geomagnetic, celestial and olfactory cues, but rarely are social interactions between individuals considered. Mounting evidence from other taxa indicates that individuals in larger groups can better sense and respond to environmental cues, thus potentially increasing their ability to navigate. Here, we propose that salmon might similarly benefit from collective navigation on their homeward journey. To explore this, we compiled data from multiple studies and found strong evidence that rates of successful homing increase with population abundance, consistent with collective navigation. We then discuss how collective navigation could benefit salmon during each stage of their seaward and homeward migrations, and complement this with a review of salmon sociality. Next, we analyse historic high‐seas catch records and provide new insight into schooling structure of salmon in the marine environment. We argue that collective navigation likely represents a presently under‐appreciated mechanism enhancing the navigational ability of salmon as well as other migratory species, and outline critical tests of our hypothesis.