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Principles for estimating natural mortality rate
No full textIn contemporary stock assessments there is increasing emphasis on how natural mortality varies with time, age, and space. But, little guidance is available for estimating this parameter. We maintain that in an exploited population, with few exceptions, contrast in fishing mortality in the data is needed to separate fishing mortality from natural mortality. Variability (contrast) in fishing mortality can be over time (inter- or intra-annual), space, and ontogeny. (The exceptions where contrast in fishing mortality is not needed are cases where information is available on population size and total catch.) High contrast in fishing mortality results in enhanced ability to estimate natural mortality. It follows that study design can be manipulated to achieve greater contrast and make more effective use of existing contrast. Integrated stock assessments afford the opportunity to enhance the needed contrast, provided the contrast is modeled explicitly
Susceptibility of vapour heat-treated “B74” mango fruit to internal disorders and mineral nutrient composition
No full textSupply of premium quality fruit to export markets is important for consumer satisfaction and repeat purchase. For ‘B74’ mango fruit, vapour heat treatment (VHT) is an export protocol for fruit fly control for market access. However, VHT has been associated with internal physiological disorders in ‘B74’ fruit. Susceptibility of ‘B74’ to internal disorders in association with VHT and flesh mineral composition was investigated. Fruit were sourced from orchards across three climatic regions of Australia: Northern Territory (NT), Far-north Queensland (FNQ), and South-east Queensland (SEQ). They were assessed over two successive seasons for internal disorders associations with mesocarp mineral composition. Flesh browning (FB) and flesh cavity with white patches (FCWP) defects were observed. FCWP was present only in VHT fruit. FB was independent of VHT. Over the two seasons, the highest FB incidence was observed in NT fruit (20 %) and the highest FCWP in FNQ fruit (65 %). FB was not observed in fruit from SEQ in either season. Flesh [Ca] and [Mg] were highest in NT fruit. [N,B], N/Ca, K/Ca, and (K+Mg)/Ca were higher (p ≤ 0.05) in fruit from SEQ. Significant (p ≤ 0.05) positive correlations between FCWP and N/Ca, K/Ca, and (K+Mg)/Ca ratios and a negative correlation between FB and [B] were discerned by linear correlation and principal component analysis. However, strength of correlation and statistical significance levels varied over regions and seasons. This inconsistency suggests that other deterministic factors also influence VHT-induced internal disorders in ‘B74’ mango. ‘Big data’ sets encompassing preharvest factors along with ‘at harvest’ flesh mineral concentrations would potentially better inform predictive modelling of internal disorders expression in ‘B74’ fruit
Integrated Pest Management in Pigeonpea: Progress and Prospects
No full textPigeonpea is one of the world's most important grain legume crops. Mostly grown and consumed in India, where it is a staple food, pigeonpea production also occurs elsewhere in Asia, Africa, Latin America and Australia. Despite widespread cultivation and staple food status, pigeonpea yields have barely increased over the last half century. The prevalence and severity of insect pests present major constraints to increasing pigeonpea yields. Two of the most significant pests of pigeonpea are the lepidopteran ‘pod-borers’–Helicoverpa armigera and Maruca vitrata. The pod fly (Melanagromyza obtusa) and several species of pod-feeding Hemiptera are also regular pests, and numerous other minor or sporadic pests have been recorded throughout the cultivated distribution of the crop. Current pigeonpea pest management practices rely heavily on the application of synthetic insecticides. Most research has focused on the management of H. armigera, M. vitrata and M. obtusa due to their damaging feeding behaviour, and the propensity of H. armigera to evolve resistance to synthetic insecticides. Not surprisingly, pest management in pigeonpea is largely based around these three major pests, particularly the lepidopteran pod-borers which appear to be more damaging to modern short-duration cultivars than to older cultivars. A large amount of research has attempted to develop pigeonpea cultivars with conventional host-plant resistance to pod-borers and pod fly, but with limited success. Future pigeonpea pest management research should take a more integrated approach, exploring underexamined areas such as: understanding how modern pigeonpea varieties and traditional landraces respond to pest herbivory, identifying what cultural control methods are available to smallholder farmers, and investigating how biological control can be incorporated into management practices. Future research has the potential to develop IPM strategies in pigeonpea and provide farmers with an alternative to an unsustainable dependence on synthetic insecticides
Novel risk assessment framework to compare shark-bite mitigation strategies
No full textHuman–wildlife conflicts (HWCs) are increasing globally and are some of the most pervasive problems for the conservation of terrestrial and marine species. Stakeholders often hold different values and concerns surrounding HWCs, and understanding these values and their relative importance among stakeholders allows for more effective decision-making. We developed a multi-objective decision analysis framework to compare and assist in determining preferred mitigation measures to reduce HWCs. We illustrate how this framework can be used to identify appropriate mitigation measures to reduce the risk of shark bites, which have been increasing worldwide and have led to ongoing controversy and debate between governments and other stakeholders. We combined expert assessment of shark-bite mitigation measures against socio-economic and environmental criteria, while accounting for subjective ranking of the importance of these performance criteria across stakeholders. Our flexible framework was tested to compare 15 mitigation measures for the Gold Coast region of Queensland, Australia, using 12 performance criteria. Results reiterated the societal shift towards non-lethal measures and highlighted which mitigation measures or performance criteria lacked information, helping to identify knowledge gaps and research needs. The flexibility of our framework makes it applicable to a broad range of contexts and HWCs and allows the incorporation of location-specific requirements and views that may vary between stakeholders. Read the free Plain Language Summary for this article on the Journal blog
Carbohydrate reserve regulation and fruit productivity in two mango cultivars at high or low planting densities
No full textEnhancing fruit productivity in mango orchards often involves increasing the number of trees planted per unit land area, yet higher planting density can lead to reduced yields per tree due to smaller canopies. Non-structural carbohydrate availability and its allocation to reproductive development are critical for tree-level productivity optimisation. This study explores the link between carbohydrate reserves and fruit yields per tree across two growing seasons (2023/24 and 2024/25). We compared starch and sugars in major storage organs, roots and trunk wood, of two mango cultivars, ‘NMBP 1243’ and ‘Keitt’, grown at two planting densities (208 and 1250 trees per hectare) in Australia. Samples were collected from six trees of each cultivar at both densities, at key phenological stages each season. We established baseline carbohydrate reserves influenced by prior cropping, assessed carbohydrate replenishment before the next fruiting cycle, and evaluated carbohydrate usage during fruit growth. Leaf stomatal conductance, density and chlorophyll content were additionally monitored as indicators of photosynthetic capacity. Subsequently, the relationships between fruit productivity and tree carbohydrate dynamics were assessed. The results suggest that ‘Keitt’ exhibits superior productivity capacity due to highly functional leaves and a greater reliance on carbohydrate reserves to support fruiting. ‘Keitt’ could be considered an ‘optimistic’ carbohydrate regulator, utilising carbohydrate resources more e iciently. In contrast, ‘NMBP 1243’ trees tend to exhibit larger vegetative canopies and appear to adopt a more ‘pessimistic’ approach to utilising carbohydrates for fruiting. ‘Keitt’ appears particularly suitable for higher planting density orchards due to its ability to regulate carbohydrate reserves and produce more fruit on a canopy volume basis
Comparative Genomics Reveals Ancient and Unique Pathogenicity Features in Australian Fusarium oxysporum f. sp. vasinfectum
No full textFusarium oxysporum f. sp. vasinfectum (Fov) is a devastating cotton pathogen. Australian Fov strains are distinguished by their ability to infect plants without nematode interaction and are genetically distinct from global Fov, classified into two vegetative compatibility groups (VCG-01111 and VCG-01112). Here, we present chromosome-level genome assemblies of a historical isolate for each Australian Fov VCG. The end-to-end gapless genome assemblies demonstrate high contiguity and completeness, with 97.7% BUSCO completeness for both isolates. Phylogenetic analysis indicates that the Australian Fov lineages diverged from other known Fov genomes over 3.6 million years ago, while VCG-01111 and VCG-01112 separated approximately 1.1 million years ago. Comparative genomics analysis identified four accessory chromosomes unique to the Australian isolates. Functional annotations revealed 14,495 and 15,342 genes in VCG-01111 and VCG-01112, respectively, with accessory chromosomes containing significantly fewer genes than core chromosomes. Ortholog analysis uncovered unique gene clusters enriched in key metabolic pathways, pathogenicity, and cell division processes. Additionally, we identified several novel lineage-specific peptides unique to each Australian isolate. This comprehensive genomic characterization provides the first insights into the unique evolutionary history of Australian Fov, distinguishing them from global Fov races. Our findings lay the foundation for understanding the genetic factors underlying their exceptional virulence, which makes Australian Fov among the most aggressive cotton pathogens worldwid
Legume production paddocks to improve beef enterprise productivity and grassland management
No full textWeaner or steer production of tropical cattle breeds for feeder or live export markets is the dominant primary industry in the seasonally-dry zone of northern Australia. Uncleared savannah woodlands and natural grasslands are key feed resources, with smaller cleared areas used for pasture development or cropping. Extended dryseasons, soils of mostly low to moderate fertility and the maturation characteristics of native grasses limit animal growth and market options for producers. Land condition decline and the associated increase in early maturing introduced grasses (Bothriochloa pertusa and Themeda quadrivalvis) are emerging issues for beef producers. Recent research in north Queensland by the Queensland Government, with support from the Australian Government and Meat and Livestock Australia, has focussed on the development and promotion of ‘production paddocks’ using deep-rooted and productive legumes (Clitoria, Desmanthus, Macroptilium, Stylosanthes). These relatively intensively-managed paddocks target the nutrition of weaners and steers during the early to mid dry season to (1) enable earlier sale or higher sale weights of cattle, and (2) encourage sustainable grazing practices through spelling other areas on the property enabled by improved animal productivity. Small-plot studies of grass x legume combinations on commercial beef properties resulted in pasture yields 2-3 times those achieved on native pastures on fertile and infertile soils. Critically, the legume component contributed leaf with high feed value (15- 20% crude protein and 8-10 MJ/kg metabolisable energy) when companion grasses had low feed value. The high quality of the dry season feed provided by legumes was confirmed using faecal sample testing
Legume establishment in challenging environments of northwest Queensland
No full textEstablishing legumes on Mitchell Grass Downs country in northwest Queensland has the potential to reduce seasonal nutritional deficiencies, and subsequently increase animal performance within beef production systems. Legumes present an opportunity to increase crude protein (14 to18%) and metabolizable energy (8 to10 MJ/ME/kg DM) in the diet, as the nutritional quality of grass dominant native pastures declines markedly during the dry season (May to October).
Recent research initiated by the Queensland Government, with support from the Australian Government and Meat and Livestock Australia (MLA), has trialled establishment of deep-rooted and productive legumes (Desmanthus, Stylosanthes) on a property 80 km northeast of Julia Creek, Queensland.
This site is characterised by naturally treeless cracking clay soils, highly variable summer-dominant rainfall, (550 mm average annual rainfall, CV=0.43) and is highly susceptible to drought. The soil contains adequate Colwell phosphorus levels for legume growth (12mg/kg), however, sulphur (MCP) is low (4.6mg/kg). Rainfall variability, highly competitive adapted annual grass species and high summer temperatures (average maximum of 38oC) make establishment of legumes difficult.
In January 2024, following 350mm of rain, uncoated Stylosanthes seabrana (Caatinga stylo, Primar) and scarified Desmanthus (Ray and Progardes) was broadcast onto cultivated strips (10 m wide) prior to further anticipated rainfall. No herbicide or fertiliser was applied. Assessment in March 2024 showed good seedling populations of desmanthus (~20/m2) with fewer Caatinga stylo (~5/ m2). In May 2024, the survival of seedling populations under a dense monoculture of Flinders grass (Iseilema spp.) was observed. Further measurements will be completed following the 2024/2025 wet season to confirm successful establishment of mature Desmanthus and Stylosanthes on this site. This research was initiated due to regional producer interest and will be utilised in extension efforts under the north Queensland Pasture Resilience Program (https://futurebeef.com.au/resources/qprp/)
Habitat use of invasive chital deer is associated with soil mineral content
No full textContext Ungulates have been introduced to many environments around the world. Some of these populations have become invasive, resulting in severe economic, social, and environmental impacts. In 1886, chital deer (Axis axis) were introduced to north Queensland, Australia, and the population has since grown and expanded. Aims To understand where chital deer are likely to occur in the future, we examined the relationship between chital deer abundance and environmental variables at two scales, namely, local and regional. Methods The local scale was surveyed using camera traps on a single property, and regional scale data were collected from a landholder survey of properties across the current distribution of chital deer in the region. Key results High predicted soil phosphorus was correlated with high relative abundance of chital deer at both the local and regional scales. In addition, at the local scale, higher predicted soil sodium content and normalised vegetation index (NDVI, ‘greenness’), close proximity to homesteads and highways, and lower canopy cover and height were strongly correlated with increased chital deer abundance. Conclusions There were more chital in areas with high predicted soil phosphorus at both local and regional scales. Implications This study has the following two implications for management: (1) areas with high predicted soil phosphorous content had the highest relative abundance of deer at both scales, and should be the focus of control efforts, and (2) such areas are more vulnerable to future invasion of chital deer and should be monitored closely
Moisture ingress and movement pattern in Australian CLT panels – a pilot study
No full textAustralian Radiata Pine Cross Laminated Timber (CLT) panels were subjected to different methods aiming to increase the overall moisture content (MC). These methods were chosen to simulate scenarios of free water contact and high humidity, which are common in subtropical climates like Australia. To mimic free water exposure, CLT samples were submersed in water, while environmental chambers were used to simulate high humidity events over different duration. Specific moisture targets were set at 20% MC for high humidity and 30% MC for free water. After achieving the desired moisture levels, the distribution of moisture through CLT panels was assessed for each method. A grid system was developed to map moisture pockets within the panels and identify pathways for moisture ingress. The findings indicate that CLT panels are unlikely to reach moisture contents above 20% MC when exposed to high humidity. However, exposure to free water resulted in a rapid increase in moisture content well above 30% MC. This suggests that heavy rain and flash flooding events, and plumbing leaks pose significant concern for CLT, warranting further investigation