Declining trends in annual catch rates of the tiger shark (Galeocerdo cuvier) in Queensland, Australia

Suitable long term species-specific catch rate and biological data are seldom available for large shark species, particularly where historical commercial logbook reporting has been poor. However, shark control programs can provide suitable data from gear that consistently fishes nearshore waters all year round. We present an analysis of the distribution of 4757 . Galeocerdo cuvier caught in surface nets and on drumlines across 9 of the 10 locations of the Queensland Shark Control Program (QSCP) between 1993 and 2010. Standardised catch rates showed a significant decline (p<. 0.0001) in southern Queensland locations for both gear types, which contrasts with studies at other locations where increases in tiger shark catch per unit effort (CPUE) have been reported. Significant temporal declines in the average size of tiger sharks occurred at four of the nine locations analysed (p<. 0.05), which may be indicative of fishing reducing abundance in these areas. Given the long term nature of shark control programs along the Australian east coast, effects on local abundance should have been evident many years ago, which suggests that factors other than the effects of shark control programs have also contributed to the decline. While reductions in catch rate are consistent with a decline in tiger shark abundance, this interpretation should be made with caution, as the inter-annual CPUE varies considerably at most locations. Nevertheless, the overall downward trend, particularly in southern Queensland, indicates that current fishing pressures on the species may be unsustainable. © 2012 Elsevier B.V.

Evaluation of aerial photography for predicting trends in structural attributes of Australian woodland including comparison with ground-based monitoring data

The accurate assessment of trends in the woody structure of savannas has important implications for greenhouse accounting and land-use industries such as pastoralism. Two recent assessments of live woody biomass change from north-east Australian eucalypt woodland between the 1980s and 1990s present divergent results. The first estimate is derived from a network of permanent monitoring plots and the second from woody cover assessments from aerial photography. The differences between the studies are reviewed and include sample density, spatial scale and design. Further analyses targeting potential biases in the indirect aerial photography technique are conducted including a comparison of basal area estimates derived from 28 permanent monitoring sites with basal area estimates derived by the aerial photography technique. It is concluded that the effect of photo-scale; or the failure to include appropriate back-transformation of biomass estimates in the aerial photography study are not likely to have contributed significantly to the discrepancy. However, temporal changes in the structure of woodlands, for example, woodlands maturing from many smaller trees to fewer larger trees or seasonal changes, which affect the relationship between cover and basal area could impact on the detection of trends using the aerial photography technique. It is also possible that issues concerning photo-quality may bias assessments through time, and that the limited sample of the permanent monitoring network may inadequately represent change at regional scales

Long-term trends in fertility of soils under continuous cultivation and cereal cropping in southern Queensland. IX. Simulation of soil carbon and nitrogen pools using CENTURY model

Cultivation and cropping of soils results in a decline in soil organic carbon and soil nitrogen, and can lead to reduced crop yields. The CENTURY model was used to simulate the effects of continuous cultivation and cereal cropping on total soil organic matter (C and N), carbon pools, nitrogen mineralisation, and crop yield from 6 locations in southern Queensland. The model was calibrated for each replicate from the original datasets, allowing comparisons for each replicate rather than site averages. The CENTURY model was able to satisfactorily predict the impact of long-term cultivation and cereal cropping on total organic carbon, but was less successful in simulating the different fractions and nitrogen mineralisation. The model firstly over-predicted the initial (pre-cropping) soil carbon and nitrogen concentration of the sites. To account for the unique shrinking and swelling characteristics of the Vertosol soils, the default annual decomposition rates of the slow and passive carbon pools were doubled, and then the model accurately predicted initial conditions. The ability of the model to predict carbon pool fractions varied, demonstrating the difficulty inherent in predicting the size of these conceptual pools. The strength of the model lies in the ability to closely predict the starting soil organic matter conditions, and the ability to predict the impact of clearing, cultivation, fertiliser application, and continuous cropping on total soil carbon and nitrogen.

Trends in therapeutic and prevention strategies for management of Bovine Mastitis: An overview

Mastitis is one of the most economically significant diseases for the dairy industry for backyard farmers in developing countries and high producing herds worldwide. Two of the major factors impeding reduction in the incidence of this disease is [a] the lack of availability of an effective vaccine capable of protecting against multiple etiological agents and [b] propensity of some of the etiological agents to develop persistent antibiotic resistance in biofilms. This is further complicated by the continuing revolving shift in the predominant etiological agents of mastitis, depending upon a multitude of factors such as variability in hygienic practices on farms, easy access leading to overuse of appropriate or inappropriate antibiotics at suboptimal concentrations, particularly in developing countries, and lack of compliance with the recommended treatment schedules. Regardless, Staphylococcus aureus and Streptococcus uberis followed by Escherichia coli, Streptococcus agalactiae has become the predominant etiological agents of bovine mastitis followed Streptococcus agalactiae, Streptococcus dysagalactiae, Klebsiella pneumonia and the newly emerging Mycoplasma bovis. Current approaches being pursued to reduce the negative economic impact of this disease are through early diagnosis of infection, immediate treatment with an antibiotic found to either inhibit or kill the pathogen(s) in vitro using planktonic cultures and the use of the currently marketed vaccines regardless of their demonstrated effectiveness. Given the limitations of breeding programs, including genetic selection to improve resistance against infectious diseases including mastitis, it is imperative to have the availability of an effective broad-spectrum, preferably cross-protective, vaccine capable of protecting against bovine mastitis for reduction in the incidence of bovine mastitis, as well as interrupting the potential cross-species transmission to humans. This overview highlights the major etiological agents, factors affecting susceptibility to mastitis, and the current status of antibiotic-based therapies and prototype vaccine candidates or commercially available vaccines against bovine mastitis as potential preventative strategies. © 2013 Tiwari JG, et al.

Water-use efficiency and productivity trends in Australian irrigated cotton: a review

The aim of this review is to report changes in irrigated cotton water use from research projects and on-farm practice-change programs in Australia, in relation to both plant-based and irrigation engineering disciplines. At least 80% of the Australian cotton-growing area is irrigated using gravity surface-irrigation systems. This review found that, over 23 years, cotton crops utilise 6-7ML/ha of irrigation water, depending on the amount of seasonal rain received. The seasonal evapotranspiration of surface-irrigated crops averaged 729mm over this period. Over the past decade, water-use productivity by Australian cotton growers has improved by 40%. This has been achieved by both yield increases and more efficient water-management systems. The whole-farm irrigation efficiency index improved from 57% to 70%, and the crop water use index is >3kg/mm.ha, high by international standards. Yield increases over the last decade can be attributed to plant-breeding advances, the adoption of genetically modified varieties, and improved crop management. Also, there has been increased use of irrigation scheduling tools and furrow-irrigation system optimisation evaluations. This has reduced in-field deep-drainage losses. The largest loss component of the farm water balance on cotton farms is evaporation from on-farm water storages. Some farmers are changing to alternative systems such as centre pivots and lateral-move machines, and increasing numbers of these alternatives are expected. These systems can achieve considerable labour and water savings, but have significantly higher energy costs associated with water pumping and machine operation. The optimisation of interactions between water, soils, labour, carbon emissions and energy efficiency requires more research and on-farm evaluations. Standardisation of water-use efficiency measures and improved water measurement techniques for surface irrigation are important research outcomes to enable valid irrigation benchmarks to be established and compared. Water-use performance is highly variable between cotton farmers and farming fields and across regions. Therefore, site-specific measurement is important. The range in the presented datasets indicates potential for further improvement in water-use efficiency and productivity on Australian cotton farms.

Frost trends and their estimated impact on yield in the Australian wheatbelt

Radiant spring frosts occurring during reproductive developmental stages can result in catastrophic yield loss for wheat producers. To better understand the spatial and temporal variability of frost, the occurrence and impact of frost events on rain-fed wheat production was estimated across the Australian wheatbelt for 1957–2013 using a 0.05 ° gridded weather data set. Simulated yield outcomes at 60 key locations were compared with those for virtual genotypes with different levels of frost tolerance. Over the last six decades, more frost events, later last frost day, and a significant increase in frost impact on yield were found in certain regions of the Australian wheatbelt, in particular in the South-East and West. Increasing trends in frost-related yield losses were simulated in regions where no significant trend of frost occurrence was observed, due to higher mean temperatures accelerating crop development and causing sensitive post-heading stages to occur earlier, during the frost risk period. Simulations indicated that with frost-tolerant lines the mean national yield could be improved by up to 20 through (i) reduced frost damage (~10 improvement) and (ii) the ability to use earlier sowing dates (adding a further 10 improvement). In the simulations, genotypes with an improved frost tolerance to temperatures 1 °C lower than the current 0 °C reference provided substantial benefit in most cropping regions, while greater tolerance (to 3 °C lower temperatures) brought further benefits in the East. The results indicate that breeding for improved reproductive frost tolerance should remain a priority for the Australian wheat industry, despite warming climates.