Experimental assessment of the effects of sublethal salinities on growth performance and stress in cultured tra catfish (Pangasianodon hypophthalmus)

The effects of a range of different sublethal salinities were assessed on physiological processes and growth performance in the freshwater ‘tra’ catfish (Pangasianodon hypophthalmus) juveniles over an 8-week experiment. Fish were distributed randomly among 6 salinity treatments [2, 6, 10, 14 and 18 g/L of salinity and a control (0 g/L)] with a subsequent 13-day period of acclimation. Low salinity conditions from 2 to 10 g/L provided optimal conditions with high survival and good growth performance, while 0 g/L and salinities >14 g/L gave poorer survival rates (p < 0.05). Salinity levels from freshwater to 10 g/L did not have any negative effects on fish weight gain, daily weight gain, or specific growth rate. Food conversion ratio, however, was lowest in the control treatment (p < 0.05) and highest at the maximum salinities tested (18 g/L treatment). Cortisol levels were elevated in the 14 and 18 g/L treatments after 6 h and reached a peak after 24-h exposure, and this also led to increases in plasma glucose concentration. After 14 days, surviving fish in all treatments appeared to have acclimated to their respective conditions with cortisol levels remaining under 5 ng/mL with glucose concentrations stable. Tra catfish do not appear to be efficient osmoregulators when salinity levels exceed 10 g/L, and at raised salinity levels, growth performance is compromised. In general, results of this study confirm that providing culture environments in the Mekong River Basin do not exceed 10 g/L salinity and that cultured tra catfish can continue to perform well.     

The potential of dry olive cake in a practical diet for juvenile hybrid tilapia,Oreochromis niloticus × Oreochromis aereus

A feeding trial of 84 days was carried out to evaluate the effects of olive cake (OC) on growth, feed utilization, digestibility of nutrient, haematological values and some blood chemistry parameters of juvenile hybrid tilapia (Oreochromis niloticus × Oreochromis aereus). Four diets were prepared including OC at levels of 0, 120, 240 and 360 g kg^?1. Twenty fish per tank (initial weight 8.58 ± 0.09 g) were randomly distributed into 200‐L fibreglass tanks. Final body weight and specific growth rate of fish fed with diets OC12 were not significantly different compared to fish fed with the control diet. The best feed conversion rate and protein efficiency rate were obtained from the fish fed with the control and OC12 diets. Growth performance, feed conversion rate and protein efficiency rate of fish fed diets with OC incorporation levels of more than 12 per cent tended to decrease significantly (P < 0.05) compared to the control and OC12 diet groups. The apparent digestibility coefficients (ADC) of dry matter significantly decreased (P < 0.05) with the increase of dietary OC levels, whereas the ADC of protein was not affected by dietary treatment. The ADC of lipid of fish fed with control and OC12 diets were significantly (P < 0.05) higher than those of fish fed with OC24 and OC36 diets. Mean corpuscular haemoglobin, cholesterol and triglycerides were affected by dietary OC level. The findings of this study show that OC can be incorporated to diets of juvenile hybrid tilapia up to 120 g kg^?1 without any adverse effect on fish growth and feed utilization.     

Sodium fluoride influences calcium metabolism resulting from the suppression of osteoclasts in the scales of nibbler fish <Emphasis Type="Italic">Girella punctata</Emphasis>

The influence of sodium fluoride (NaF) on calcium metabolism was examined in nibbler fish (marine teleosts). Two days after the administration of NaF (5 μg/g of body weight) (around 10^?4 M in fish), we showed that plasma calcium levels significantly decreased in NaF-treated nibbler fish. In addition, we detected fluoride in the treated scales by use of a scanning electron microscope with an energy-dispersive X-ray microanalysis, indicating that NaF directly affects their scales. Therefore, the influence of NaF on osteoblasts and osteoclasts in the scales was examined. In the scales of NaF-injected nibbler fish, tartrate-resistant acid phosphatase (TRAP) (osteoclastic marker enzyme) decreased, although alkaline phosphatase (osteoblastic marker enzyme) was activated. To confirm the effect of NaF on osteoclasts, furthermore, the mRNA expressions of osteoclastic markers (matrix metalloproteinase-9 and TRAP) were decreased significantly 2 days after incubation. In barred knifejaws, plasma calcium levels decreased as they did in nibbler fish. Therefore, NaF functions in both osteoblasts and osteoclasts and then influences calcium metabolism in marine fish. In the marine environment, high levels of fluoride (1.2–1.5 mg F^?/l) (around 10^?5–10^?4 M) are present in seawater. It is probable that teleosts living in seawater efficiently use fluoride to regulate their blood calcium levels.     

Detection of Herpesvirus anguillae (AngHV‐1) in European eel Anguilla anguilla (L.) originating from northern Poland—assessment of suitability of selected diagnostic methods

The Community Action Plan requests EU member states to implement measures that ensure the recovery of the severely depleted European eel stocks. One of the main threats is posed by Anguillid herpesvirus 1 (AngHV‐1) leading to increased mortality in both wild and farmed eels. Following recommendations of the OIE to minimize the risk of obtaining false‐negative results, the main aim of the study was to optimize diagnostic methods for AngHV‐1 detection using conventional PCR, nested PCR and in situ hybridization assay. While 53.3% of the individual organ samples were tested positive for AngHV‐1 by PCR, the additional virus analysis via nested PCR revealed that the actual prevalence was 93.3%. In the cell cultivation passages, a cytopathic effect was hardly found in the first two rounds. In the third passage onto cell cultures, a lytic CPE was detected. The identification and confirmation of the viruses obtained from cell cultures as well as directly from the organ tissues were proceeded by PCR, nested PCR and sequencing of the PCR products. While no positive signal was detectable in the first round by PCR using samples from the third cell culture passages, the nested PCR provided weak but visible positive signals.     

Development of real‐time and quantitative QCM immunosensor for the rapid diagnosis of Aeromonas hydrophila infection

Since bacterial infection cause a significant economic loss in fish farms, it is necessary to develop rapid diagnostic tools. Interests on label‐free biosensors have been raised for the rapid detection of aquatic pathogenic bacteria but have not been extensively studied yet. Here we report a quartz crystal microbalance (QCM) immunosensor system for the rapid and simple detection of Aeromonas hydrophila, a pathogen for fish and human, in comparison with a conventional indirect ELISA method. In QCM immunosensor system, an antibody against A. hydrophila was covalently cross‐linked to the gold surface of sensor chip and bacterial attachment was monitored as real‐time frequency shifts within 5 min. The frequency shifts were very positively related to the amounts of bacterial cells between 6.25 and 100 μg corresponding to 6 × 10⁶ to 10⁸ CFU with a high specificity. The QCM immunosensor was also able to detect bacterial cells in fish tissue extract in a dose‐dependent manner. Indirect ELISA also showed the dose‐dependent reaction and the amplified signal may allow a lower detection limit. However, QCM immunosensor system showed a more linear and reliable standard curve with R² value of almost 1 (0.9999). Moreover, detection of the bacteria was much quicker and simpler.     

Effects of species and shelterbelt structure on wind speed reduction in shelter

Live shelterbelts are common elements in coastal land areas and play an important role in reducing wind speed and sand drift. A simple measured index, that well represents relationship between shelterbelt structure and wind speed reduction, is required by landowners to enable them in establishing more effective shelterbelts. A three-dimensional crown (3D) density is proposed, which can be easily identified through shelterbelt parameters including maximum height, shelterbelt width, vertical crown/stem area ratio, and horizontal crown/stem area ratio. The utility of the index was tested in 10-year-old Casuarina equisetifolia and in 7-year-old Acacia auriculiformis shelterbelts in north central Coast of Vietnam. There was a significant negative linear relationship (R ² = 0.64, p < 0.001) between 3D density and wind speed reduction efficiency, while there was no relationship between a two-dimensional crown density and wind speed reduction efficiency. Reduction efficiency was found to increase at higher wind speeds in shelterbelts of A. auriculiformis, but not C. equisetifolia. The A. auriculiformis shelterbelt was more efficient in reducing wind speed compared to C. equisetifolia shelterbelt. The former recovered 70 % wind speed at 130 m (16.5H) leeward, while it recovered 70 % at 85 m (8H) leeward in C. equisetifolia shelterbelt.     

Stabilization of toxic metals in three contaminated soils by residual impact of lime integrated with biochar and clays

Journal of Soils and Sediments - Mine and smelter soil contaminations with Pb, Cu, Cd, and Zn have become serious problems in China, because of anthropogenic activities. Little is known about the...     

Trace Metal Contamination During Grinding of Plant Samples

Inductively coupled plasma-mass spectroscopic (ICP-MS) analysis of leaves from 22 cabbage crops in the Sa P? and B?c Hà districts of Láo Cai Province, North-Western Vi?t Nam, revealed unexpectedly high concentrations of chromium (Cr) and nickel (Ni). The concentrations were strongly linearly related (r² = 0.94), indicating sample contamination during grinding through a stainless-steel hammer mill. We tested this hypothesis in two ways. First, brown rice ground through the same mill was contaminated not only by Cr and Ni, but also cobalt (Co), iron (Fe) and molybdenum (Mo). Second, scanning electron microscopy/energy dispersive analysis of x-rays (SEM/EDS) of the ground samples revealed small fragments with co-located Fe, Cr and Ni, consistent with stainless steel wear fragments. Other grinders may perform differently and we suggest that quality assurance protocols for trace metal analysis of plants should include testing for grinder wear metals. Lastly, brown rice appears to be convenient for investigating contamination of plant tissues during grinding.     

Chemical modification of wheat protein-based natural polymers: cross-linking effect on mechanical properties and phase structures

Chemical modification of wheat protein-based natural polymer materials was conducted using glyoxal as cross-linker, and the cross-linking effect was studied on mechanical properties under different humidity conditions, the molecular motions of each component, and the phase structures/components of the whole materials. The cross-linking significantly enhanced the mechanical strength of wheat gluten (WG) materials under RH = 50%. The elongation of materials was also increased, which was in contrast to many cross-linked protein systems. The reaction mainly occurred in proteins and starch components, resulting in the formation of a stable cross-linked network with restricted molecular motions and modified motional dynamics. Although the plasticizer glycerol could also take part in the reaction with glyoxal or other components in WG especially when the glyoxal content was higher, the amount of glycerol involved in such reactions was very little. Glycerol was predominantly hydrogen-bonded with the network. The lipid component did not seem to take part in the cross-linking reaction; its mobility was promoted while its interaction with the protein-starch network was weakened after cross-linking. The formation of the cross-linked network did not enhance the hydrophobicity of the materials; the materials still adsorbed a high level of moisture under high humidity conditions (ca. RH = 85%) with no improvement in mechanical strength. In addition, further increasing the amount of glyoxal did not generate an additional strength improvement even at RH = 50%, possibly because the enhanced mobility of lipid promoted the component to be phase-separated from the WG system. To improve the water-resistant properties, the hydrophobicity of the protein macromolecules requires enhancement by other chemical modifications.     

澜湄合作机制框架下的林业减贫研究

澜湄流域国家和地区是世界上典型的贫困区域之一,澜湄流域拥有相似的气候、植物物种和地理环境,在减贫经验方面具有相互借鉴的基础。文中在分析澜湄国家贫困演变历程和现状以及森林资源状况基础上,总结我国云南省和泰国林业减贫的成功实践,结合对澜湄流域的贫困林区、森林管理机构和农户的实地调研,阐述了澜湄国家面临的挑战以及对社区林业减贫的需求,提出了澜湄流域的林业减贫对策与建议,以期助力澜湄流域减贫事业。