ORCID Profile
0000-0003-2493-3676
Current Organisation
University of Tasmania
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Publisher: Oxford University Press (OUP)
Date: 2003
DOI: 10.1016/S1054-3139(03)00093-6
Abstract: Multi-year tag-recovery models can be used to derive estimates of age- and year-specific annual survival rates and year-specific instantaneous fishing and natural mortality rates. The latter, which are often of interest to fisheries managers, usually can only be estimated when the tag-reporting rate (λ) and the short-term tag-induced mortality and tag-shedding rate (φ) are known a priori. We present a new multi-year tagging model that permits estimation of instantaneous mortality rates independently of φλ, provided tagged animals from two adjacent size groups are released simultaneously. If the two size groups comprise animals just above and below the minimum harvestable size limit, then it is possible to estimate year-specific instantaneous fishing and natural mortality rates after 2 yr of tagging and tag-recovery. In addition to the standard assumptions of multi-year tag-recovery models, it is necessary to assume that recruited animals have equal selectivity, pre-recruited animals become fully recruited in 1 or 2 yr, and the size groups experience the same natural mortality rate. Applicability of the model to the Tasmania southern rock lobster (Jasus edwardsii) fishery is evaluated using a simulation model and parameters based on data from the lobster fishery assumptions are likely to be met and precision should be adequate if at least 1000 animals are tagged per year in each size group.
Publisher: American Astronomical Society
Date: 10-2023
Publisher: Springer Science and Business Media LLC
Date: 19-10-2007
Publisher: American Astronomical Society
Date: 25-02-2021
Abstract: We present K -band interferometric observations of the PDS 70 protoplanets along with their host star using VLTI/GRAVITY. We obtained K -band spectra and 100 μ as precision astrometry of both PDS 70 b and c in two epochs, as well as spatially resolving the hot inner disk around the star. Rejecting unstable orbits, we found a nonzero eccentricity for PDS 70 b of 0.17 ± 0.06, a near-circular orbit for PDS 70 c, and an orbital configuration that is consistent with the planets migrating into a 2:1 mean motion resonance. Enforcing dynamical stability, we obtained a 95% upper limit on the mass of PDS 70 b of 10 M Jup , while the mass of PDS 70 c was unconstrained. The GRAVITY K -band spectra rules out pure blackbody models for the photospheres of both planets. Instead, the models with the most support from the data are planetary atmospheres that are dusty, but the nature of the dust is unclear. Any circumplanetary dust around these planets is not well constrained by the planets’ 1–5 μ m spectral energy distributions (SEDs) and requires longer wavelength data to probe with SED analysis. However with VLTI/GRAVITY, we made the first observations of a circumplanetary environment with sub-astronomical-unit spatial resolution, placing an upper limit of 0.3 au on the size of a bright disk around PDS 70 b.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 31-03-2017
Abstract: Distributions of Earth's species are changing at accelerating rates, increasingly driven by human-mediated climate change. Such changes are already altering the composition of ecological communities, but beyond conservation of natural systems, how and why does this matter? We review evidence that climate-driven species redistribution at regional to global scales affects ecosystem functioning, human well-being, and the dynamics of climate change itself. Production of natural resources required for food security, patterns of disease transmission, and processes of carbon sequestration are all altered by changes in species distribution. Consideration of these effects of bio ersity redistribution is critical yet lacking in most mitigation and adaptation strategies, including the United Nation's Sustainable Development Goals.
Publisher: Elsevier BV
Date: 11-1995
Publisher: Springer Science and Business Media LLC
Date: 16-09-2011
Publisher: Wiley
Date: 05-2008
DOI: 10.1577/T06-272.1
Publisher: Wiley
Date: 22-07-2014
DOI: 10.1111/MEC.12795
Abstract: We apply qPCR molecular techniques to detect in situ rates of consumption of sea urchins (Centrostephanus rodgersii and Heliocidaris erythrogramma) by rock lobsters (Jasus edwardsii). A non-lethal method was used to source faecal s les from trap-caught lobsters over 2 years within two no-take research reserves. There was high variability in the proportion of lobsters with faeces positive for sea urchin DNA across years and seasons dependent on lobster size. Independent estimates of lobster predation rate on sea urchins (determined from observed declines in urchin abundances in the reserves relative to control sites) suggest that rates of molecular prey detection generally overestimated predation rates. Also, small lobsters known to be incapable of directly predating emergent sea urchins showed relatively high rates of positive tests. These results indicate that some lobsters ingest non-predatory sources of sea urchin DNA, which may include (i) ingestion of C. rodgersii DNA from the benthos (urchin DNA is detectable in sediments and some lobsters yield urchin DNA in faeces when fed urchin faeces or sediment) (ii) scavenging and/or predation by rock lobsters on small pre-emergent urchins that live cryptically within the reef matrix (although this possibility could not be assessed). While the DNA-based approach and direct monitoring of urchin populations both indicate high predation rates of large lobsters on emergent urchins, the study shows that in some cases absolute predation rates and inferences of predator-prey interactions cannot be reliably estimated from molecular signals obtained from the faeces of benthic predators. At a broad semi-quantitative level, the approach is useful to identify relative magnitudes of predation and temporal and spatial variability in predation.
Publisher: Inter-Research Science Center
Date: 19-08-2009
DOI: 10.3354/MEPS08096
Publisher: Elsevier BV
Date: 05-2014
Publisher: Springer Science and Business Media LLC
Date: 21-01-2022
Publisher: Elsevier BV
Date: 09-2010
Publisher: Inter-Research Science Center
Date: 26-02-2008
DOI: 10.3354/MEPS07227
Publisher: Elsevier BV
Date: 04-2007
Publisher: Inter-Research Science Center
Date: 14-10-2010
DOI: 10.3354/MEPS08778
Publisher: Elsevier BV
Date: 04-2011
Publisher: Cambridge University Press (CUP)
Date: 28-04-2008
DOI: 10.1017/S0007485308005981
Abstract: We demonstrate the use of molecular techniques to detect specific prey consumed by the southern rock lobster ( Jasus edwardsii ). A quick and non-lethal method was used to collect rock lobster faecal material and a molecular protocol was employed to isolate prey DNA from faecal s les. The isolated DNA was lified using the polymerase chain reaction (PCR) with PCR primers designed to target specific prey items. Feeding experiments determined that DNA from black-lipped abalone ( Haliotis rubra ) and sea urchins ( Centrostephanus rodgersii and Heliocidaris erythrogramma ) can be detected in rock lobster faecal s les within seven hours and remains present for up to 60 h after ingestion.
Publisher: Springer Science and Business Media LLC
Date: 29-09-2014
Publisher: Wiley
Date: 2008
DOI: 10.1002/JEZ.445
Abstract: This study examined the endocrine and reproductive correlates of reproduction in 636 female and 468 male draughtboard sharks (Cephaloscyllium laticeps) captured from southeastern Australia. Females were oviparous and displayed a single external-type ovary with a maximum follicle diameter of 35 mm. Vitellogenesis commenced at a follicle diameter of 10 mm. Females showed a constant overlap between follicular recruitment, ovarian growth, and egg laying. The male reproductive tract consisted of paired testes with spermatocysts undergoing diametric development. Plasma levels of the presumptive gonadal steroids, testosterone (T), 17beta-estradiol (E2), progesterone (P4), and 11-ketotestosterone (11-KT males only) were correlated with morphological developmental stages of the gonads. In females, E2 increased as the follicle developed before declining as the follicle reached maturity. T remained low during the first stages of ovarian growth and increased as the follicle reached maturity. P4 showed a peak just before ovulation. In males, T was the only hormone that varied with maturity, increasing in adults E2 and P4 were present at low plasma concentrations in males and did not change with stage of gonadal development. 11-KT was undetectable at all times. Endocrine changes in draughtboard sharks were consistent with hormonal correlates reported for other species and suggest roles for E2( in females) and T (in both sexes) in gametogenesis and P4 in maturational events in females.
Publisher: Wiley
Date: 04-2012
DOI: 10.1111/J.1095-8649.2012.03249.X
Abstract: A combination of passive tracking and conventional tagging was used to provide insight into the movement patterns of the draughtboard shark Cephaloscyllium laticeps, the most common catshark in coastal areas of southern Australia. A series of acoustic receivers deployed throughout south-eastern Tasmania as well as a receiver array along an isolated reef, Crayfish Point Reserve (CPR), passively tracked 25 C. laticeps from January to July 2003. Cephaloscyllium laticeps were present from 4 to 98 days. The majority of the C. laticeps stayed within the CPR where most in iduals were active throughout the night. They were found actively moving (i.e. when a C. laticeps was consecutively detected by two or more non-overlapping receivers, suggesting the in idual was moving) and spending periods of minor movements (i.e. when an in idual was consecutively detected by only one receiver, suggesting it was at rest). The length of these minor movements periods, observed both day and night, ranged from 1 h to 5 days. In addition to passive tracking, 1552 conventionally tagged C. laticeps were released in the eastern and south-western coastal areas of Tasmania and within the CPR between January 2000 and April 2007. The CPR showed a higher recapture rate, 38%, than eastern and south-western areas where the recapture rates were 10 and 3%, respectively. Within the CPR, 36% of the sharks were recaptured on multiple occasions. The maximum time at liberty ranged from 1 month to 7 years. The majority of the C. laticeps were recaptured in the vicinity of where they were released (<10 km), although larger longer-term movements of up to 300 km were recorded. The large amount of multiple recaptures within the CPR, in addition to acoustic tagging results, indicated a high degree of site fidelity for C. laticeps. This isolated reef appears to be an important habitat for this species, and therefore, the current protection status of this area is probably beneficial for the conservation of C. laticeps.
Publisher: Elsevier BV
Date: 05-2014
Publisher: Elsevier BV
Date: 10-2008
Publisher: Springer Science and Business Media LLC
Date: 24-12-2014
Publisher: Springer Science and Business Media LLC
Date: 18-01-2013
Publisher: Wiley
Date: 21-10-2010
DOI: 10.1111/J.1095-8649.2010.02810.X
Abstract: Research longline s ling was conducted seasonally from December 2006 to February 2009 to investigate the occurrence and population structure of the broadnose sevengill shark Notorynchus cepedianus in coastal areas of south-east Tasmania. Notorynchus cepedianus showed a consistent temporal trend in seasonal occurrence in Norfolk Bay characterized by high abundances in summer to near absence in winter. This pattern was less pronounced in the Derwent Estuary, where fish were still caught during winter. The absence of smaller total length (L(T) ) classes (<80 cm) from the catches suggests that N. cepedianus are not using these coastal habitats as nursery areas. Of the 457 in iduals tagged, 68 (15%) were recaptured. Time at liberty ranged from 6 days to almost 4 years and all but one of the recaptures were caught in its original tagging location, suggesting site fidelity. The large number of N. cepedianus in these coastal systems over summer indicates that these areas are important habitats for this species and that N. cepedianus may have a significant influence on community dynamics through both direct and indirect predator-prey interactions.
Publisher: Elsevier BV
Date: 08-2011
Publisher: Proceedings of the National Academy of Sciences
Date: 29-12-2009
Abstract: A key consideration in assessing impacts of climate change is the possibility of synergistic effects with other human-induced stressors. In the ocean realm, climate change and overfishing pose two of the greatest challenges to the structure and functioning of marine ecosystems. In eastern Tasmania, temperate coastal waters are warming at approximately four times the global ocean warming average, representing the fastest rate of warming in the Southern Hemisphere. This has driven range extension of the ecologically important long-spined sea urchin ( Centrostephanus rodgersii ), which has now commenced catastrophic overgrazing of productive Tasmanian kelp beds leading to loss of bio ersity and important rocky reef ecosystem services. Coincident with the overgrazing is heavy fishing of reef-based predators including the spiny lobster Jasus edwardsii . By conducting experiments inside and outside Marine Protected Areas we show that fishing, by removing large predatory lobsters, has reduced the resilience of kelp beds against the climate-driven threat of the sea urchin and thus increased risk of catastrophic shift to widespread sea urchin barrens. This shows that interactions between multiple human-induced stressors can exacerbate nonlinear responses of ecosystems to climate change and limit the adaptive capacity of these systems. Management actions focused on reducing the risk of catastrophic phase shift in ecosystems are particularly urgent in the face of ongoing warming and unprecedented levels of predator removal from the world's oceans.
Publisher: Elsevier BV
Date: 03-2003
Publisher: CSIRO Publishing
Date: 2001
DOI: 10.1071/MF01196
Abstract: Fisheries scientists and managers want precise estimates of fishing and natural mortality for assessments and management decisions. Because tagging can be an expensive option, maximizing potential benefits requires careful consideration of experimental design. We evaluated four options for improving the precision of estimates by conducting Monte Carlo simulations of a fishery patterned after that for the rock lobsters in north-western Tasmania, Australia. Improving tag-reporting rate and increasing the duration of the tagging study provided greater improvements in precision than increasing either the number of lobsters tagged per tagging event or the number of tagging events each year. A design based on twice-a-year tagging for three years to determine tagreporting rate followed by an additional two or more years of once-a-year tagging provided the most precise estimates of natural mortality of all the designs considered. This design was also cost effective relative to the other options, but tag-reporting rate must be constant over the period of the study. If constancy cannot be assumed, then years of multiple tagging events may have to be interspersed among the years with single tagging events. Further improvements in mortality estimates from this multiyear tagging model could be achieved with improved tagreporting rate.
Publisher: Elsevier BV
Date: 12-2003
Publisher: Wiley
Date: 10-01-2020
DOI: 10.1002/AQC.3264
Publisher: Wiley
Date: 28-01-2009
DOI: 10.1111/J.1365-2818.2009.03118.X
Abstract: We present a novel approach for deconvolution of 3D image stacks of cortical tissue taken by mosaic/optical-sectioning technology, using a transmitted light brightfield microscope. Mosaic/optical-sectioning offers the possibility of imaging large volumes (e.g. from cortical sections) on a millimetre scale at sub-micrometre resolution. However, a blurred contribution from out-of-focus light results in an image quality that usually prohibits 3D quantitative analysis. Such quantitative analysis is only possible after deblurring by deconvolution. The resulting image quality is strongly dependent on how accurate the point spread function used for deconvolution resembles the properties of the imaging system. Since direct measurement of the true point spread function is laborious and modelled point spread functions usually deviate from measured ones, we present a method of optimizing the microscope until it meets almost ideal imaging conditions. These conditions are validated by measuring the aberration function of the microscope and tissue using a Shack-Hartmann sensor. The analysis shows that cortical tissue from rat brains embedded in Mowiol and imaged by an oil-immersion objective can be regarded as having a homogeneous index of refraction. In addition, the amount of spherical aberration that is caused by the optics or the specimen is relatively low. Consequently the image formation is simplified to refraction between the embedding and immersion medium and to 3D diffraction at the finite entrance pupil of the objective. The resulting model point spread function is applied to the image stacks by linear or iterative deconvolution algorithms. For the presented dataset of large 3D images the linear approach proves to be superior. The linear deconvolution yields a significant improvement in signal-to-noise ratio and resolution. This novel approach allows a quantitative analysis of the cortical image stacks such as the reconstruction of biocytin-stained neuronal dendrites and axons.
Publisher: CSIRO Publishing
Date: 2009
DOI: 10.1071/MF09030
Abstract: The draughtboard shark Cephaloscyllium laticeps is a common oviparous catshark found in Australia. Studies on the reproductive seasonality of catsharks and the reproductive endocrinology of oviparous elasmobranchs are limited to a few species. The aim of the present study was to investigate the reproductive seasonality and embryo development of C. laticeps using morphological and endocrine parameters. Macroscopic examinations of the reproductive system and embryo stages were recorded. The steroid hormones 17β- oestradiol (E2) and progesterone (P4) were measured in females, and testosterone (T) in both sexes. Females laid eggs throughout the year, but with a peak in egg deposition between January and June. Female T levels were higher in the middle of the year. Elevated P4 values coincided with the period of egg deposition, whereas E2 was depressed in the middle of the egg deposition stage. Females laid eggs in the absence of males for 15 months, and eggs were laid in pairs at monthly intervals. Hatching occurred after 12 months. Variability in gonadosomatic index, percentage of sperm in seminal vesicles, and plasma T levels for males indicated that males were reproductively active throughout the year.
Publisher: Elsevier BV
Date: 02-2014
Publisher: EDP Sciences
Date: 10-2009
DOI: 10.1051/ALR/2009039
Publisher: Elsevier BV
Date: 2008
Publisher: Inter-Research Science Center
Date: 14-07-2010
DOI: 10.3354/MEPS08649
Publisher: Oxford University Press (OUP)
Date: 15-09-2011
Abstract: Godwin, R. M., Frusher, S., Montgomery, S. S., and Ovenden, J. 2011. Telomere length analysis in crustacean species: Metapenaeus macleayi, Sagmariasus verreauxi, and Jasus edwardsii. – ICES Journal of Marine Science, 68: 2053–2058. Estimates of age and growth in crustaceans have been historically problematic and presented significant challenges to researchers. Current techniques of age determination provide valuable data, but also suffer from disadvantages. Telomeric DNA has been proposed as an age biomarker because it shortens with age in some species. In this study, the feasibility of using telomere length (TL) to estimate age was examined in the school prawn Metapenaeus macleayi and the spiny lobsters Sagmariasus verreauxi and Jasus edwardsii. Carapace length (CL) was used as a surrogate for age, and terminal restriction fragment assays were used to test the relationship between TL and size. Degradation of telomeric DNA with time during storage significantly influenced TL estimates, particularly for M. macleayi. TLs obtained from species in this study were 10–20 kb. No relationship between CL and TL was detected for any of the test species, and TL did not differ between male and female M. macleayi. TLs of J. edwardsii pueruli were unexpectedly shorter than those of J. edwardsii adults. The suitability of TL as an age biomarker in crustaceans may be limited, but further research is needed to elucidate telomere dynamics in these species with their different life histories and lifespans.
Publisher: Springer Science and Business Media LLC
Date: 12-08-2014
Publisher: Elsevier BV
Date: 06-2013
Publisher: Springer Science and Business Media LLC
Date: 04-05-2014
Publisher: CSIRO Publishing
Date: 2006
DOI: 10.1071/MF05238
Abstract: Indices of recruitment are often derived from trap surveys. If legal-sized lobsters inhibit smaller ones from entering traps, the overall catch-rate may depend on population composition and not just on overall abundance, and recruitment strength can be overestimated as average length decreases in a population. A controlled field experiment was used to examine whether trapping inhibition of Jasus edwardsii occurred during spring (November) or summer (February) in south-eastern Tasmania. Four treatments were applied. Baited traps were seeded with either: one large female, one large male or two sublegal-sized female lobsters. Baited traps with no seed were used as a control. Seeded traps always caught fewer sublegal-sized lobsters than control traps. When catches in both seasons were examined by sex of entrants, seeded traps caught fewer small lobsters than control traps in 11 of 12 comparisons. However, a strong inhibitory effect was observed only for female-seeded traps during summer. The data obtained in the present study suggest that sublegal-sized indices of recruitment are likely to be influenced in summer by the number of large females present. Spring trials suggest that corrections to a sublegal-catch index may be unnecessary during this season, but more work is required in order to better understand the complex, sex-specific and seasonal patterns of interactions of this species.
Publisher: Wiley
Date: 20-01-2008
No related grants have been discovered for Stewart Frusher.