12903 research outputs found
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Exploring the green break of season and green date over northern Australia
No full textContext: In northern Australia, livestock production relies heavily on dryland pastures, whose growth is strongly controlled by wet season rainfall. Knowledge of the likely timing of the first productive pasture after the long dry season – marked by the green cover onset (GCO) - can help graziers establish an appropriate stocking rate based on the available fodder at the end of the previous growing season. Objective: This study focuses on the ‘green break of season' date (GBOS), defined as the first day after 1 September when a threshold amount of rainfall (e.g., 50 mm) is accumulated over a 3-day period. This rainfall-based metric aims to coincide with the annual onset of effective pasture growth (GCO) in northern Australia. Methods: Using robust model-derived estimates of green pasture cover at a representative location in northeastern Queensland we compute the Green Cover Onset (GCO), defined as the first day after 1 October on which modelled green cover reaches or exceeds a specific threshold. This study explores the relationship between GCO and the GBOS for different 3-day accumulated rainfall thresholds (10–80 mm, in increments of 10 mm). We further explore the ‘green date’ (GD), defined as the 70th percentile of the distribution of GBOS dates, calculated over a long historical period (1900–2023) in northern Australia using daily rainfall observations from the Scientific Information for Land Owners (SILO). We then analyse, how the phase of the El Niño-Southern Oscillation (ENSO) influences the GBOS distribution. Results and conclusions: The strongest relationship between GBOS and GCO is found defining the GBOS as the first occurrence of 50 mm of rainfall accumulated over 3 days (R2 > 0.94). This correlation is stronger than that between the commonly used Northern Rainfall Onset (50 mm accumulated after 1 September) and GCO (R2 = 0.62), with a regression slope closer to 1 and a y-intercept closer to zero, indicating a better one-to-one relationship with the GCO. This suggests that the GBOS is a more effective indicator for estimating the onset of productive pastures. Additionally, our analysis reveals that during El Niño years, the reliable GBOS (the 70th percentile of GBOS for ENSO-influenced years) occurs slightly later than the GD for all years, with no significant difference. In contrast, during La Niña years, it occurs significantly earlier. This pattern is consistent across regions in northern Australia, showing that El Niño delays and La Niña advances the northern wet season. Significance: This study paves the way for the development of a seasonal GBOS prediction product, which will help livestock producers in making more informed and effective management decisions
Do some tiger sharks prefer beaches? Insights for shark management from a broad-scale comparative tracking study
No full textHuman coastal populations and water-based recreation are growing, increasing potential for interactions with sharks near beaches. At popular beaches in Australia's Great Barrier Reef Marine Park, potentially dangerous sharks are tagged using acoustic tags and relocated away from bathing areas by the Queensland Shark Control Program. This includes tiger sharks Galeocerdo cuvier, one of three species involved in most unprovoked shark bites globally. A broad-scale acoustic tracking network off eastern Australia was used to assess movement of relocated sharks and potential for recurrent risks to beachgoers posed by relocation. Over more than two years, movements of 51 relocated tiger sharks were compared to 82 sharks tagged at locations up to 135 km away from monitored beaches in the marine park (which extends ∼2300 km along Australia's northeast coast). Monitored beaches were visited by 43.1 % of relocated sharks, after median intervals of three months, compared to only 6.1 % of sharks tagged elsewhere in the marine park. Despite return visits by some individuals over extended periods, beach use remained limited, with low residency and mostly transient visits (<30 min) peaking at night, limiting risks to humans. Network analysis revealed relatively localised movements (median network diameter: 123 km), particularly in north Queensland where seasonal migrants from temperate areas were less common inshore. Our results indicate beaches are low-use areas within the home ranges of some sharks. These findings highlight challenges to coexistence with potentially dangerous sharks at beaches but support the efficacy of non-lethal relocation of tiger sharks for immediate reduction of risk
Spatial Modelling of Miconia calvescens Invasion Risk in North Queensland Rainforests to Refine Surveillance Planning
No full textMiconia calvescens is one of the worst invaders of tropical rainforest environments in the Asia‐Pacific region. Introduced as a garden plant in north Queensland Australia, naturalised infestations in the rainforests emerged 30 years ago. The National Tropical Weeds Eradication Program (NTWEP) was established to coordinate national eradication efforts. While the program targets multiple invasive plant species, around 75% of surveillance effort is expended on M. calvescens . This small rainforest tree produces abundant seed, which is dispersed by birds and forms highly persistent soil seedbanks. Significant long‐term search effort is required to detect plants, across variable and challenging terrain. We developed a spatial model of M. calvescens invasion risk to inform and refine decisions on surveillance planning. The model considers environmental factors that support plant establishment and persistence, and dispersal factors that support the introduction of viable seed by birds. The model output is a spatial risk layer showing susceptibility to plant invasion, categorised from very low to very high. Susceptibility was predicted from known locations of mature M. calvescens plants at three time steps (December 2016, 2019 and 2022). Model predictions for 2016 and 2019 were retrospectively evaluated against actual plant detections and search effort by NTWEP in the following 3 years. Results indicate that both models accurately predicted actual detections in areas classified as very high to moderate risk. While most of the model‐predicted high‐risk areas were actually searched, much search effort was also expended in low to ‘no’ risk areas where relatively few plants were found. The model prediction for 2022 was evaluated against current surveillance area coverage targets, demonstrating that current planning effort could be refined by invasion risk. We recommend that our model can inform risk‐based surveillance planning while still maintaining confidence that surveillance coverage is suitably comprehensive for the needs of an eradication program
Publicly-shared DNA barcodes and citizen science images provide new evidence on the establishment and spread of a lantana biological control agent, Orphanostigma haemorrhoidalis (Lepidoptera, Crambidae)
No full textOrphanostigma haemorrhoidalis (Guenée) (Lepidoptera, Crambidae), indigenous to the Americas, was widely used in the Old World for the biological control of Lantana camara L. (Verbenaceae) from the 1950s to the 1980s. DNA barcodes from the Barcode of Life Data System (BOLD) and citizen scientist images from the iNaturalist and Afromoths websites were used to detect the establishment and spread of O. haemorrhoidalis in countries where it has not previously been reported. Analysis of DNA barcodes showed that there are two genetically distinguishable populations of O. haemorrhoidalis in the Americas, one in the south-eastern USA and the other widespread in the rest of the Neotropics. The two populations were introduced into different parts of the World and subsequently spread. We used DNA barcodes from BOLD to clarify that a population from Florida is established in Hawai’i, Australia and Fiji, while a population from Trinidad is established in parts of mainland Africa (including new records for Cameroon, Nigeria and Ghana), Madagascar, Mauritius and La Réunion. New country records for O. haemorrhoidalis were established from iNaturalist images from Eswatini, Kenya and Mozambique, and from Afromoths for Tanzania
The complete genome sequence of a novel legume closterovirus from Norfolk Island
No full textA novel species in the genus Closterovirus, family Closteroviridae, has been identified by high throughput sequencing in legume samples collected during plant pathogen surveys on Norfolk Island in 2014. The complete genome sequence of 16,815 nucleotides was obtained from a French bean (Phaseolus vulgaris) plant with symptoms of interveinal chlorosis in the older leaves. Complete or near complete coding sequences for the 10 open reading frames were also obtained from a second French bean plant, and batch samples of white clover (Trifolium repens) and pea (Pisum sativum). All isolates shared 99.7–99.9% nucleotide identity, indicating they are members of the same virus species
Identifying capacity limitations and training needs using a stock assessment game
No full textThe technical capability of stock assessment analysts, along with characteristics of their operating environment, often limits the development of suitable population dynamics models and affects the accuracy of estimated quantities used for fisheries management. Following a series of training workshops focused on the Stock Synthesis and Stock Assessment Continuum Tool packages, Australian stock assessment scientists were invited to participate in a hypothetical stock assessment “Game” to explore the repercussions , for assessment, of different levels of experience and technical capability in an informal “consequence-free” manner. A fishery data set was generated using a simulation model that represented a stock distributed over 12 regions and harvested by three fishing fleets. The simulation model was made complex by including spatial structure, time-varying selectivity for some fleets, and changes over time in expected recruitment due to the effects of an environmental driver. The analysts self-organized into six (mostly within-agency) groups and reported estimates of current biomass, current depletion and advice regarding the possibility of local depletion. The results of the Game were used to evaluate the approaches used by the various groups and to identify areas where future training would be most beneficial. The results highlighted opportunities for additional training in spatially-explicit population dynamics modelling, the use of methods for pre-processing monitoring data to select appropriate fleet and population structures, as well as the use of methods to provide values related to growth and natural mortality. The groups treated the Game more seriously than was originally intended by the organizers, with several analysts concerned that any errors or assumptions that were mis-matched with the simulated reality may have brought embarrassment to themselves and their agency. Care should therefore be taken that simulation experiments intending to foster collaboration and learning do so in an explicitly understood risk-free environment. Overall, the Game proved valuable in contributing to the development of an Australian community of practice for stock assessment and identifying how to strengthen assessment capabilities
Stock assessment of Australian east coast Spanish mackerel (Scomberomorus commerson), with data to June 2024
No full textSpanish mackerel (Scomberomorus commerson) is a large pelagic species of fish. On the east coast of Australia they form a single genetic stock, between the Cape York Peninsula in northern Queensland and Newcastle on the New South Wales mid coast. In these waters, Spanish mackerel can live for up to 26 years, grow to over 30 kg in weight and reach maturity between 2 and 4 years of age, as observed in Fisheries Queensland data.
Previous assessments estimated the stock at 39–51% of unfished levels in 2009, 30–50% in 2016 and 17% (14–27%) in 2020. Several key aspects of this assessment differ from past assessments. Firstly, membership of the project team that guides the assessment was expanded, to include fishery stakeholders (one commercial and one recreational fisher) as well as an independent scientist. Secondly, this assessment benefited from updated data through to June 2024, as well as new data provided through the Fisheries Research and Development Corporation (FRDC) funded project ‘Addressing the uncertainties in the assessment and management of Queensland east coast Spanish mackerel’ (project number: 2021-111). Thirdly, the previous assessment underwent two external reviews, and feedback from these has been incorporated. Finally, the key outputs were constructed as an ensemble across multiple model scenarios, rather than selecting a particular preferred scenario.
All assessment inputs and outputs are referenced on a financial year basis— ‘2024’ means ‘July 2023 to June 2024’.
The assessment used an age-structured model with an annual time step, fitted to standardised catch rates, length composition data and age-at-length composition data. The model incorporated Queensland and New South Wales data spanning the period 1911–2024, collected from the commercial, recreational and charter sectors.
Several scenarios were run covering a range of modelling assumptions and sensitivity tests. All scenarios were optimised using Markov chain Monte Carlo (MCMC) to better explore the robustness of the models. From these exploratory scenarios a final ‘ensemble’ of six scenarios were chosen for inclusion in summary reporting. This ensemble indicates that the biomass ratio at the beginning of 2025 was between 17% and 62% of unfished levels with a median of 34% of unfished levels
Phosphine as a possible alternative to methyl bromide for the phytosanitary treatment of wood products
No full textPhosphine (PH3) has gained momentum as a phytosanitary treatment to control quarantine pests in exported wood products. Originally used as a grain fumigant, its use increased after methyl bromide was banned for its ozone-depleting properties. While the effectiveness of PH3 against grain pests is well-established, its efficacy for wood products requires review due to growing adoption. We observed insufficient evidence supporting PH3 as a broad-spectrum quarantine treatment for wood products from peer-reviewed/gray literature and international groups. We assessed 41 research articles covering 29 insect species, 1 nematode, and 11 fungi, and observed that while PH3 is effective against some forest insects, it generally fails to meet quarantine treatment standards and is ineffective against nematodes and fungi. Our analysis highlights concerns over the effectiveness of PH3 as a broad-spectrum treatment for wood products. Many studies lack the quality needed to meet contemporary standards. We strongly recommend that National Plant Protection Organizations review the efficacy data supporting PH3 use for wood products to strengthen biosecurity systems
Thermal biology of Hypogeococcus pungens (Hemiptera: Pseudococcidae) explains its variable performance as a classical biological control agent for Harrisia martinii (Cactaceae) in Australia
No full textThe mealybug, Hypogeococcus pungens Granara de Willink (Hemiptera: Pseudococcidae), was released in Australia as a biological control agent for Harrisia martinii (Labour.) Britton (Cactaceae) in 1975. Although the mealybug successfully established in all released locations, its impact has been variable among regions, possibly as a result of climatic differences. Life-history traits (settling time, survival, development time, female reproduction, adult longevity) were compared at 6 constant temperatures (15 to 40 °C) in the laboratory. The mealybug settled on H. martinii at all temperatures tested, but at 15 °C and 40 °C, insects failed to develop and died. Temperature affected female size, fecundity, and integrated performance, all of which were highest at 25 °C. A linear model that fitted temperature to development time indicated a lower developmental threshold of 14.5 °C for both male and female mealybugs. CLIMEX models were developed for the mealybug and its host, H. martinii, and used to investigate the suitability of different regions of Australia, where H. martinii occurs for Hy. pungens. The Hy. pungens CLIMEX model suggests that cold stress limits mealybug growth in southern Queensland and that mealybug performance will vary between regions based on local temperatures. Locations with extreme low winter and extreme high summer temperatures are likely to have the most constrained populations. This may account for the observed differences in the effectiveness of Hy. pungens as a biological control agent at locations within the established range of H. martini in Australia
Field assessment of current and improved surveillance traps for fruit flies (Diptera: Tephritidae) in Australia
No full textExotic fruit fly (Diptera: Tephritidae) surveillance in Australia predominantly relies on male-lure trapping. We assessed the performance of 3 traps currently used in Australian fruit fly surveillance: Lynfield, Modified Steiner, and Paton; against 3 improved versions: Enhanced Steiner, Enhanced Paton, and Enhanced Paton-10 mm. Laboratory trials revealed existing traps failed to exclude rain, and drained poorly, which guided our trap modifications. These modified traps were field-tested across 2 seasons and 4 locations in tropical and subtropical areas, with trap efficacy measured by total flies trapped, quality of fly DNA by real-time PCR, and weatherability observations. During the dry season, the Enhanced Paton trap outperformed all other traps in terms of fruit fly catch rates, a trend that continued in the wet season. While there was no discernible variation in DNA quality among flies caught by the 6 trap types, wet trap contents negatively affected DNA quality, with the incidence of wet trap catches influenced by trap design. No wet flies were observed in the Enhanced Paton trap, a result of the modifications made, which included a 3° entrance tube with a 42° angled roof. Overall, the Enhanced Paton trap proved to be a superior alternative to existing designs, offering higher fly capture rates and better-quality specimens for both morphological and molecular identification