The Effects of Water Exchange on Production of Metapenaeus macleayi and Water Quality in Experimental Pools

Two experiments in 4 m diameter, plastic lined pools were conducted nt two densities, 20 shrimp/ m² and 47 shrimp/m², to determine the effects of water exchange rate on the production of the penaeid shrimp Metapenaeus macleayi (Haswell) and on water quality variables. Water exchange rates ranged from 0–40%/d for the 9 wk low density experiment and 0–20%/d for the 8 wk high density experiment. With the exception of mass mortality after prawns escaped from one pool (0% water exchange) on the last day of the high density experiment, shrimp performance indices (survival, weight gain, biomass gain and food conversion ratio) were not significantly affected by water exchange rate. During both experiments water exchange significantly reduced the concentrations of phosphorus and plant pigments (chlorophyll a, b and c and pheophytin) but had no significant effect on pH or the concentration of ammonia or nitrite plus nitrate. Data from this study suggest that while production ponds should not be managed for extended periods without water exchange, simply increasing daily water exchange rates may not necessarily increase shrimp growth or survival. Water exchange can reduce nutrient concentrations and phytoplankton densities but most of the reduction occurs at water exchange rates of between 0–5%/d.     

Morphological studies on the venous drainage of the trachea in the neck of sheep.

Systemic venous drainage of the cervical portion of the trachea from the cricoid cartilage to the sternal notch was observed in 50 adult sheep. In all animals, the first five to six tracheal rings starting at the cricoid cartilage were drained by the thyroid veins (v. thyroideae) bilaterally to the external jugular veins (v. jugularis externa). A venous complex draining the remaining cervical portion of the trachea was observed only on the left side of the trachea. This complex drained to the cranial vena cava (vena cava cranialis). India ink or Evans blue dye were infused into small vessels draining this area for verification. Variations in this venous complex were classified into three types based upon length of trachea drained. Type I was found in 26%, type II found in 58%, and type III found in 16% of the sheep studied and drained 23 +/- 5%, 58 +/- 11% and 78 +/- 10% of the cervical portion of the trachea, respectively. Blood flow from this area of the trachea was 85 +/- 28 mL/min/100 g wet issue. This study identified and classified the venous drainage of the cervical portion of the trachea in sheep.     

An Investigation into Behavioural Indicators of Stress in Juvenile Scallops

Recessing and righting behaviour requires a big energetic cost to scallops and if the animals are already weakened by the stress of handling, exposure to air and transport they may find if difficult to carry out these manoeuvres. The objectives of this study were to determine the preferred sediment of scallop (Pecten maximus) spat and to determine the recessing and righting behaviour of spat under a dessication stress. The results showed that the time taken to recess was indirectly proportional to the mean sediment size of the sediment. When using the 'preferred' sediment, recessing and righting speed was indirectly proportional to the degree of exposure to air experienced by the animals. Thus by removing seasonal and size variables we were able to demonstrate a clear relationship between quality and behaviour in juvenile scallops. This test is therefore not only sensitive to changes in spat quality but is also a very quick and simple test to perform.     

Calibration of a common shortwave multispectral camera system for quantitative agricultural applications

Unmanned aerial systems (UAS) for collecting multispectral imagery of agricultural fields are becoming more affordable and accessible. However, there is need to validate calibration of sensors on these systems when using them for quantitative analyses such as evapotranspiration, and other modeling for agricultural applications. The results of laboratory testing of a MicaSense (Seattle, WA, USA) RedEdge? 3 multispectral camera and MicaSense Downwelling Light Sensor (irradiance sensor) system using a calibrated integrating sphere were presented. Responses of the camera and irradiance sensor were linear over many light levels and became non-linear at light levels below expected real-world, field conditions. Simple linear corrections should suffice for most light conditions encountered during the growing season. Using an irradiance sensor or similar system may not properly account for light variability in cloudy or partly cloudy conditions as also identified by others. A simple stand for aiding in reference panel imaging was also described, which may facilitate repetitive, consistent reference panel imaging.

     

Effects of pond preparation and feeding rate on production of Penaeus monodon Fabricius, water quality, bacteria and benthos in model farming ponds

Fibreglass pools with sediment were used as model farming ponds to investigate the interactive effects of pond preparation and feeding rate on prawn production, water quality, bacterial dynamics, abundance of benthos and prawn feeding behaviour. Pools were either fertilised 1 month (prepared) or 2 days (unprepared) prior to stocking and either ‘high’ or ‘low’ feeding rates were used. The ‘high’ rate was 5.0% (range 4–8%) wet prawn biomass/day and was similar to that recommended for commercial farms. The ‘low’ rate was 2.5% (range 2–4%) wet prawn biomass/day. Juvenile Penaeus monodon (2.0–7.5 g) were stocked at 15 prawns/m² and were cultured for 71 days. With the exception of one prepared, high feeding-rate pool where mass mortality (> 80%) of prawns occurred following an interruption to aeration, prawn survival was high (> 86%) and was unaffected by preparation, feeding rate or their interaction. Pond preparation improved growth and biomass gain by about 20%. Growth was 4% higher with the higher feeding rate but biomass gain was not affected and, as food conversion ratio was much worse, use of the lower feeding rate offers considerable scope to reduce production costs, especially during cooler periods. There was no interaction in relation to growth between pond preparation and feeding rate. Meiofauna were more abundant, and prawns grew faster, in prepared pools than unprepared pools at the start of the experiment. However, changes in bacterial dynamics or meiofauna abundance over time did not explain reductions in prawn growth over time. In general, water quality was reduced in pools receiving the high feeding rate compared with low feeding rate pools. Other interactive effects of pond preparation and feeding rate on water quality, bacteria, benthos and prawn feeding behaviour are discussed.     

Textural Optimization of Shelf‐Stable Bread: Effects of Glycerol Content and Dough‐Forming Technique

The effects of glycerol content and dough‐forming method on the physical, textural, and sensory characteristics of shelf‐stable bread were determined. Bread dough was produced with 0, 2, 4, and 6% nominal glycerol content, and formed into rolls by either dough‐dividing or extrusion‐forming methodologies. Baked products were evaluated by uniaxial compression and fitting of stress‐strain data to a three‐parameter mathematical model. A trained sensory panel quantified textural attributes using magnitude estimation methodology. Selected characteristics were also judged by an untrained consumer panel. Sensoryinstrumental relationships were determined. Products were tested instrumentally after different storage intervals to determine effects of glycerol level and dough‐forming process on degree of firming. Results showed that extrusion‐forming produced, on average, relatively more dense and less deformable products than did the dough‐dividing method; extrusionformed samples also had greater sensory firmness and were less similar to an ideal sensory texture. However, high glycerol concentrations in extrusion‐formed products gave sensory profiles that were substantially closer to the ideal. Sensory firmness and chewiness were closely correlated with parameters of power law functions that described compression behavior. Glycerol reduced ultimate firmness after storage.     

Enhanced dissipation of chrysene in planted soil: the impact of a rhizobial inoculum

Results from an innovative approach to improve remediation in the rhizosphere by encouraging healthy plant growth and thus enhancing microbial activity are reported. Mixed grass-legume systems, together with microbial inoculants, were used to remediate a polycyclic aromatic hydrocarbon (chrysene) spiked agricultural soil. Inoculants were symbiotic rhizobia, which may play an important role in rhizoremediation by increasing plant and root growth. An inoculum of an isolate of Rhizobium leguminosarum bv. trifolii, selected for PAH tolerance, was produced using a peat carrier. The inoculum and white clover (Trifolium repens L.), were planted into soils with ryegrass (Lolium perenne L.). The soils spiked with chrysene (500 mg kg⁻¹) then aged for 4 weeks. Shoot- and root-biomass of plants, and the amount of root nodulation, were determined. Rhizobial populations, soil pH and soil nitrogen were also monitored throughout the trial. In addition, the ability of the inoculated rhizobial strain to utilise chrysene as a sole carbon source was assessed. Direct uptake and/or degradation of chrysene by the clover and ryegrass did not occur to a significant degree. Enhanced losses of chrysene were seen in planted, non-sterile soils that contained a rhizobial inoculum. No direct degradation of chrysene by R. leguminosarum bv. trifolii was observed and no enhanced losses of PAHs were detected in sterile soils after inoculation with rhizobia. Results suggest that the enhanced dissipation of chrysene, observed in the non-sterile planted inoculated pots, was not a result of degradation of chrysene by R. leguminosarum bv. trifolii. The symbiotic association with R. leguminosarum bv. trifolii improved plant vigour and growth in inoculated planted treatments. This may have stimulated the rhizospheric microflora to degrade chrysene.     

Response of Douglas-fir leaf area index and litterfall dynamics to Swiss needle cast in north coastal Oregon, USA

Sources of variation in leaf area index (LAI; m² of projected leaf area per m² of ground area) and its seasonal dynamics are not well known in managed Douglas-fir stands, despite the importance of leaf area in forecasting forest growth, particularly in stands impacted by insects or disease. The influence of Swiss needle cast (SNC) on coastal Douglas-fir (Pseudotsuga menziesii var. menziesii [Mirb] Franco) LAI and litterfall dynamics was quantified by destructively sampling 122 stems from 36 different permanent plots throughout north coastal Oregon, USA, and by monitoring litterfall for 3 years in 15 of these plots. LAI, total annual litterfall, and the seasonal distribution of foliage and fine woody litterfall were all influenced by stand structural attributes, physiographic features, and SNC severity. Mean LAI in this study was 5.44 ± 2.16. The relatively low LAIs were attributed primarily to the effects of SNC on foliage retention, and secondarily to its direct measurement by hierarchical foliage sampling in contrast to indirect measurement by light interception or tree allometry. For a given stand structure and SNC severity, LAI was 36% greater in the fall after current year foliage was fully developed and older aged classes had not yet senesced. Annual litterfall expressed as a proportion of LAI at the start of the growing season varied from 0.13 to 0.53 and declined with increasing initial LAI. SNC also shifted more of the annual foliage litterfall to earlier in the spring. Fine woody litterfall experienced a different seasonal shift as the peak occurred later in the year on sites with high SNC, but this only occurred on northerly aspects. Defoliation from the endemic SNC pathogen can drastically reduce LAI and change both total and seasonal foliage litterfall patterns.     

Influence of cultivation on the distribution of phosphorus in three soils from NE Scotland and their aggregate size fractions

Abstract. The effect of cultivation on the P properties of whole soils and aggregate sizes separated from them was investigated for soil developed on three types of parent material. Cultivation, with associated fertilizer additions, increased both the total soil P content and extractable P of the whole soils. When the soils were separated into aggregate sizes (< 2, 2-52, 53-150 and 151 2000 μm), total soil P and resin extractable P increased with decreasing aggregate size. Water extractable inorganic P exhibited the opposite trend, while concentrations of water extractable organic P were similar from each aggregate size. Eroded aggregates can adsorb P or release P to solution, the extent of which will be dependent upon a combination of soil attributes and the prevailing solution conditions. The resulting equilibrium P concentration (EPC) of the eroded material will be markedly different from that of the whole soil. By increasing the P content, particularly of the smaller sized aggregates it is likely that the EPC of the eroded material would favour greater P desorption.