Social aspects of the sustainability of integrated multi-trophic aquaculture

A pilot project in the Bay of Fundy, Canada, is growing kelps, mussels, and salmon in an integrated multi-trophic aquaculture (IMTA) system. Biological and economic results are positive, but social acceptability is also a critical component of aquaculture sustainability. Focus group sessions with several segments of the population (restaurateurs, residents of communities near aquaculture facilities, and the general population) were held and the participants’ knowledge of, and opinions on, IMTA were recorded. Most participants felt that IMTA had the potential to reduce the environmental impacts of salmon farming, benefit community economies, and improve industry competitiveness and sustainability. All felt that seafood produced in IMTA systems would be safe to eat and 50% of the participants were willing to pay 10% more for these products if labelled as such. The participants felt that IMTA appears to be an improvement over current monoculture practices and would be cautiously welcomed in the marketplace. A promotional campaign educating the general public, food distributors, and other industry stakeholders about the positive benefits of IMTA would go a long way in gaining mainstream acceptance of this aquaculture practice.     

Presence and genetic variability of Piscine orthoreovirus genotype 1 (PRV‐1) in wild salmonids in Northern Europe and North Atlantic Ocean

Piscine orthoreovirus genotype 1 (PRV‐1) is widespread in farmed Atlantic salmon (Salmo salar L.) populations in northern Europe, Canada and Chile. PRV‐1 occurs in wild fish in Norway and Canada; however, little information of its geographical distribution in wild populations is currently available, and the effect of PRV‐1 infection in wild populations is currently unknown. In this study, we present the findings of a survey conducted on 1,130 wild salmonids sampled in Denmark, Sweden, Ireland, Faroe Islands, France, Belgium and Greenland between 2008 and 2017. PRV‐1 is reported for the first time in wild salmonids in Denmark, Sweden, Faroe Island and Ireland. The annual PRV‐1 prevalence ranged from 0% in France, Belgium and Greenland to 43% in Faroe Islands. In total, 66 samples tested positive for PRV‐1, including Atlantic salmon broodfish returning to spawn and Atlantic salmon collected at the feeding ground north of Faroe Islands. The phylogenetic analysis of S1 sequences of the PRV‐1 isolates obtained in this survey did not show systematic geographical distribution. This study sheds light on the spread and genetic diversity of the virus identified in populations of free‐living fish and provides rationale for screening wild broodfish used in restocking programmes.     

Nitrous Oxide Emissions in Response to ESN and Urea Application in a No-Till Barley Cropping System

We investigated the effect of environmentally smart nitrogen (ESN) fertilizer on nitrous oxide (N₂O) emissions under no-till barley (Hordeum vulgare L.) production over 3 years at three sites in Alberta, Canada. Treatments included two barley cultivars, with ESN and urea applied at 1× and 1.5× the recommended rate, and herbicide at 50% and 100% of registered in-crop rates. Cumulative N₂O emissions over the growing season were low (0.11 to 1.32 kg nitrogen (N) per hectare or 0.05–0.22 g N kg^?1 grain yield), and not affected by barley cultivars or herbicide rates in all nine site-years, nor by fertilizer type or rate in seven out of nine site-years. However, average N₂O emissions from ESN were 15% lower (P = 0.05) than urea across all site-years. Our results suggest ESN could play a role in reducing N₂O emissions, but the reduction will depend on rainfall events and crop N utilization.     

A comprehensive approach for assessing the economic contribution of forage and livestock improvement options to smallholder farming enterprises

The importance of livestock production activities to improving the livelihoods of smallholder farming households and the efficiency of their underlying farming systems is increasingly recognized.A rapid increase in livestock numbers, especially beef cattle, and special purpose forages is being promoted for smallholder farms which have traditionally undertaken subsistence cropping activities or simple livestock rearing activities using low quality feedstuffs.Because limited plantings of specialized forages combined with a poor knowledge of animal nutrition are a challenge to establishing sustainable livestock enterprises, much public policy and research is now being focused on the use of new forages and improved feeding practices.A number of economic studies have suggested that specialized forage growing and livestock feeding activities can make a positive contribution to smallholder welfare.The studies have typically compared the total level of farm or household income with and without livestock activities.Little attention is given to how much the new forage or livestock activities actually contribute to or draw resources from other farm activities to assess their real economic contribution to the enterprise, and the availability of simple tools to assist in making such assessments are limited.This paper describes a simple modelling approach that was developed for an Australian Centre for International Agricultural Research(ACIAR)-supported project to explore the real as opposed to apparent economic impact of integrating improved forages and livestock within smallholder farming systems in the Red Soils region of south-central China.Application of the model is demonstrated using a simple case study of a smallholder enterprise that plans to introduce a new beef cattle rearing activity to its existing farm activity mix.The case study highlights the importance of explicitly valuing transfers of resources between different farm activities to gauge the real contribution of those activities to economic returns.     

Theoretical and Empirical Relationships Between Oat Test Weight and Groat Proportion

Test weight and groat proportion are two very important quality characteristics of oat grain. In this study, we pose the hypothesis that these two characteristics are related through characteristics of grain density. Test weight is defined as the product of kernel density and packing proportion. Groat proportion, in theory, is the ratio of the groat mass to the kernel mass. We present two theoretical constructions expressing test weight in terms of groat proportion, packing proportion and kernel density components. To test these, we have applied measurements of test weight, groat proportion, kernel density components, and packing proportion of 18 oat cultivars grown at six environments. Whereas the groat proportion alone accounted for only 34% of the variation in test weight, our theoretical constructions that included groat proportion could account for ≤82% of variation in test weight. Also, we present previously undescribed variation in oat kernel density components across genotypes and environments. Although the kernel density alone could account for most of the variation in test weight across genotypes, packing proportion appeared to be more important in describing variation in test weight of a genotype across different environments. We observed significant variation in both groat and hull density which, together with groat proportion, described most of the variation in kernel density.     

Measurements of ozone deposition to a potato canopy

Potatoes are an important staple crop, grown in many parts of the world. Although ozone deposition to many vegetation types has been measured in the field, no data have been reported for potatoes. Such measurements, including the latent-heat flux, were made over a fully grown potato field in central Scotland during the summer of 2006, covering a 4-week period just after rainfall and then dry, sunny weather. The magnitude of the flux was typical of many canopies showing the expected diurnal cycles. Although the bulk-canopy stomatal conductance declined as the field dried out (～300 mmol-O₃ m^?2 s^?1 to ～70 mmol-O₃ m^?2 s^?1), the total ozone flux did not follow the same trend, indicating that non-stomatal deposition was significant. Over a dry surface non-stomatal resistance (R_ns) was 270–450 s m^?1, while over a wet surface R_ns was ～50% smaller and both decreased with increasing surface temperature and friction velocity. From the variation with relative humidity (RH) it is suggested that three processes occur on leaf surfaces: on a very dry surface ozone is removed by thermal decomposition, possibly enhanced by photolytic reactions in the daytime and so R_ns decreases as temperature increases; at 50–70% RH a thin film of liquid blocks the “dry” process and resistance increases; above 60–70% RH sufficient surface water is present for aqueous reactions to remove ozone and resistance decreases.