Degradation of chlorophenoxyacid herbicides in aqueous media,using a novel electrochemical method†

The degradation of five chlorophenoxyacid herbicides has been studied using an electrochemical method based on the Fenton reaction (simultaneous reduction of dioxygen and ferric ions). The method consists of electrosynthesizing OH^· radicals, which react rapidly with chlorophenoxyacids in aqueous media. HPLC and GC-MS analysis show the formation of polyhydroxyphenols and quinones in a first step, and the complete destruction of the aromatic nucleus upon exhaustive electrolysis. This offers a possible way for the depollution of natural waters containing chlorophenoxyacid pesticide residues. © 1999 Society of Chemical Industry.     

Evidence of fish spillover from freshwater protected areas in lakes of eastern Ontario

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Achieving sustainable aquaculture: Historical and current perspectives and future needs and challenges

Important operational changes that have gradually been assimilated and new approaches that are developing as part of the movement toward sustainable intensive aquaculture production systems are presented via historical, current, and future perspectives. Improved environmental and economic sustainability based on increased efficiency of production continues to be realized. As a result, aquaculture continues to reduce its carbon footprint through reduced greenhouse gas emissions. Reduced use of freshwater and land resources per unit of production, improved feed management practices as well as increased knowledge of nutrient requirements, effective feed ingredients and additives, domestication of species, and new farming practices are now being applied or evaluated. Successful expansion into culture of marine species, both off and on shore, offers the potential of substantial increases in sustainable intensive aquaculture production combined with integrative efforts to increase efficiency will principally contribute to satisfying the increasing global demand for protein and food security needs.     

The stock structure of grey mackerel Scomberomorus semifasciatus in Australia as inferred from its parasite fauna

The scombrid Scomberomorus semifasciatus is an important component of inshore fisheries in tropical Australia. Data on the parasite fauna of 593 fish from areas off northern and eastern Australia were examined for evidence of discrete fish populations. The parasites used were juveniles of Pterobothrium pearsoni, Callitetrarhynchus gracilis, Anisakis simplex (sensu latu) and Terranova sp. Tukey Kramer pairwise comparisons gave significant differences in the abundances of two or more parasites between fish from the east coast, the eastern Gulf of Carpentaria and the remainder of northern Australia. Multivariate analysis gave further evidence of differences and the results suggest that at least 4 populations or stocks of grey mackerel occur along the northern and eastern coastline of Australia.     

Influence of barley inclusion method and protease supplementation on growth performance,nutrient utilisation,and gastrointestinal tract development in broiler starters

The influence of the method of barley inclusion(fine,coarse and whole barley)in a wheat-based diet and protease supplementation(0 and 0.20 g/kg)on growth performance,nutrient utilisation and gastrointestinal tract development of broilers(d 1 to 21)was evaluated in a 3
2 factorial arrangement.Whole barley(WB)grains were ground in a hammer mill to pass through the screen sizes of 2.5 and 8.0 mm to achieve fine(FB)and coarse(CB)barley particle sizes,respectively.A total of 288,one-day-old male broilers were allotted to 36 cages(6 cages/treatment;8 birds/cage).There was no significant(P>0.05)interaction between barley inclusion method and protease for any growth performance or nutrient utilisation parameters.Birds fed diets containing CB and WB showed higher(P<0.05)weight gain,and digestibility of dry matter,nitrogen,calcium,gross energy,and ileal digestible energy compared to those fed FB diets.Compared to the birds fed FB diets,feed per gain was lower(P<0.05)in birds fed diets made of WB.Fat digestibility of the birds fed CB was higher(P<0.05)than those fed FB and WB birds.Compared to FB and CB diets,inclusion of WB resulted in heavier(P<0.05)gizzards but reduced(P<0.05)gizzard pH.Supplemental protease,however,had no effects(P>0.05)on growth performance and nutrient utilisation,most likely due to the well balanced digestible amino acids and high inherent digestibility of protein in the basal diet,and/or the presence of exogenous carbohydrase and phytase.In conclusion,the present results showed that the inclusion of coarsely ground and whole barley in a wheat-based diet can enhance nutrient and energy utilisation and is beneficial to the growth performance of young broilers.     

Determining minimum sample size for the conditioned Latin hypercube sampling algorithm

In digital soil mapping (DSM), a fundamental assumption is that the spatial variability of the target variable can be explained by the predictors or environmental covariates. Strategies to adequately sample the predictors have been well documented, with the conditioned Latin hypercube sampling (cLHS) algorithm receiving the most attention in the DSM community. Despite advances in sampling design, a critical gap remains in determining the number of samples required for DSM projects. We propose a simple workflow and function coded in R language to determine the minimum sample size for the cLHS algorithm based on histograms of the predictor variables using the Freedman-Diaconis rule for determining optimal bin width. Data preprocessing was included to correct for multimodal and non-normally distributed data, as these can affect sample size determination from the histogram. Based on a user-selected quantile range (QR) for the sample plan, the densities of the histogram bins at the upper and lower bounds of the QR were used as a scaling factor to determine minimum sample size. This technique was applied to a field-scale set of environmental covariates for a well-sampled agricultural study site near Guelph, Ontario, Canada, and tested across a range of QRs. The results showed increasing minimum sample size with an increase in the QR selected. Minimum sample size increased from 44 to 83 when the QR increased from 50% to 95% and then increased exponentially to 194 for the 99% QR. This technique provides an estimate of minimum sample size that can be used as an input to the cLHS algorithm.     

Functions for estimating aboveground biomass of birch in Norway

A suite of regional allometric aboveground biomass functions were derived for Betula pubescens and Betula pendula for Norwegian conditions. The data consisted of 67 trees sampled throughout Norway. A total of 14 component functions were developed for total aboveground, total stem, stemwood, stem bark, live crown, live branch, leaf, and dead branch biomass using combinations of diameter at breast height and height as predictor variables. Application of the derived functions to existing local southern Norwegian mountain birch and regional Swedish biomass datasets indicated an overall good predictive ability of the developed functions. However, the functions produced slight underestimates, suggesting that the respective birch populations had differing biomass allocation patterns. When the developed functions were applied to Norwegian National Forest Inventory data, they produced slightly higher biomass stock and stock change estimates than what is obtained using existing Swedish functions. The higher estimates were evident in the north, central, and western part of Norway, while estimates were similar in southeastern Norway where growing conditions are most similar to Swedish conditions. The analysis indicates that the derived functions are the best available for regional birch biomass stock and stock change estimation in Norway.     

Wildlife–livestock interactions in a western rangeland setting: Quantifying disease-relevant contacts

Disease transmission between wild ungulates and domestic livestock is an important and challenging animal health issue. The potential for disease transmission between wildlife and livestock is notoriously difficult to estimate. The first step for estimating the potential for between-species disease transmission is to quantify proximity between individuals of different species in space and time. This study estimates second-order statistics of spatio-temporal location data from radio-collared free-ranging deer, elk and cattle in northeast Oregon. Our results indicate, that when observed simultaneously, elk and cattle occur in closer proximity to each other than what would be expected based on general space use of these species. The same is true for deer and elk but not for deer and cattle. Our analysis also demonstrates that average distances between cattle and elk are largely driven by rare events of close co-mingling between the species, which extend over several hours. Behavioral causes for these co-mingling events are currently unknown. Understanding the causes for such events will be important for designing grazing practices that minimize wildlife–livestock contacts.