Associate Professor Troy Gaston

© 2019 Shanghai Ocean University In south-eastern Australia, the same baited, round traps (comprising 50¿57-mm mesh netting) are used to target giant mud, Scylla serrata and blue swimmer crabs, Portunus armatus in spatially separated fisheries. Both fisheries are characterised by the common, problematic discarding of undersized portunids (<85 and 65 mm carapace length; CL for S. serrata and P. armatus) and fish (yellowfin bream, Acanthopagrus australis). This poor selectivity was addressed here in two experiments assessing the utility of (1) traps partially or completely covered in larger mesh (91 mm to match the minimum legal size of the smaller P. armatus), and then (2) any cumulative benefits of fitting species-specific escape gaps. In experiment 1, there were no differences among catches of legal-sized portunids associated with either partial, or complete trap coverage with larger mesh. Irrespective of mesh coverage, both designs of 91-mm traps also retained significantly fewer (by up to 42%) undersized P. armatus and A. australis. In experiment 2, replicate traps completely covered in 91-mm mesh were tested against conventional traps comprising 56-mm mesh, and traps with the same mesh sizes, but also three escape gaps configured for either S. serrata (46 × 120 mm) or P. armatus (36 × 120 mm) (i.e. four treatments in total). All modified traps maintained catches of legal-sized S. serrata, and only the 91-mm traps with escape gaps caught fewer legal-sized P. armatus. Fewer undersized S. serrata, P. armatus and A. australis (mean catches reduced by up to 49%) were retained in all larger-meshed than small-meshed traps, and in all of those traps with escape gaps (by up to 95%) than without. While there were no significant cumulative benefits of escape gaps in larger-meshed traps (measured by a statistical interaction), there was a trend of fewer unwanted catches overall. These data support configuring portunid traps with mesh sizes matching the morphology of the smallest legal-sized target species. But, simply retroactively fitting escape gaps in existing, smaller-meshed traps will also realize positive selectivity benefits.

© 2020, Crown. Variation in salinity is one of the principal changes in estuarine physicochemistry that can impact the productivity of estuarine species. The effect of salinity on the mortality, growth, and metabolite profiles of juvenile Eastern School Prawn (Metapenaeus macleayi) was evaluated across a salinity gradient ranging from 0.2¿36 over 60¿days. Survival was >70% for salinity treatments other than the lowest salinity. Survival was 0% in the lowest salinity and all prawns had died within 3¿days. Salinity did not appear to impact relative growth across the range of salinities examined. In contrast, relative somatic condition was greater at lower salinities and was negatively correlated with salinity, indicating lower salinities promote enhanced somatic condition in School Prawn. Total fatty acid concentration showed no relationship with salinity or somatic condition index. However, total fatty acid concentration did have a significant positive relationship with total amino acid concentration. Total amino acid concentration showed no linear relationship with salinity or somatic condition index. Quantitative profiling of individual fatty acids and amino acids showed some changes in response to salinity. Alpha-aminoadipic acid showed a significant positive relationship with salinity. These complex patterns suggest several shifts in cellular chemistry may occur throughout the salinity range investigated, potentially with metabolic consequences. These results highlight the complex responses of estuarine crustaceans to changes in salinity.

© 2016 Elsevier B.V. Dietary habits and intra- and inter-specific trophic ecology of co-occurring Lepidotrigla mulhalli and L. vanessa from south-eastern Australia were analysed using stomach content and stable isotope ratios (d13C and d15N). Both species are bottom-feeding carnivores that consumed mainly benthic crustaceans, but teleosts were also abundant in the diet of larger L. vanessa. Non-metric multidimensional scaling (nMDS) ordination and analysis of similarity (ANOSIM) of dietary data revealed significant inter-specific dietary differences; i.e. food resource partitioning. Carbon (d13C) and nitrogen (d15N) stable isotope values were similar between L. mulhalli and L. vanessa, however, suggesting similar trophic positioning. Ontogenetic changes in diet composition and stable isotope values were evident. As L. vanessa grew, they preyed upon larger individuals, such as teleosts and caridean shrmips, but no such trend was observed in the diets of L. mulhalli. Adults of both species were significantly enriched in 15N relative to juvenile conspecifics thus supporting these data. Consequently, in this study, both methodologies, i.e. stomach content and stable isotope analyses, provided evidence of inter- and/or intra-specific dietary segregations and trophic niche partitioning between co-occurring L. mulhalli and L. vanessa off Tasmanian waters.

© 2016 Cultural ecosystem services (CES) are the non-material benefits obtained from ecosystems that contribute to human well-being. They are often under-represented in ecosystem services assessments due to difficulties identifying and valuing intangible attributes. This risks a lack of understanding and consideration of CES by decision-makers. A systematic review was done on coastal and marine CES to identify: geographic distribution of research; effective methods for assessing CES; specific habitats/ecosystems that supply CES; subcategories most frequently addressed; and knowledge gaps. Results revealed limited information exists about coastal and marine CES. There is a disparity in the global distribution of studies with little knowledge about CES in developing countries, as well as a disparity within developed countries; with most research undertaken in Europe and North America. There is a dearth of information on CES derived from specific coastal and marine habitats/ecosystems, reflecting a poor understanding of socio-ecological relationships and the different values people assign to these areas. There is a need to develop indicators with the capacity to measure and track changes in CES over time. Participatory approaches using qualitative methods were most effective in identifying CES; however, these lacked a deliberative element that would provide a comprehensive assessment of shared values in public areas. Overall, publications typically theorised about the usefulness of data on CES to inform and support decision makers, and more research is required on how qualitative data on CES can be represented for practical use by coastal and marine resource managers, and the value of these in the real world.

Copyright © 2016 John Wiley & Sons, Ltd. Biodiversity loss caused by invasive species is particularly problematic in freshwater ecosystems, which are among the world's most threatened habitats. Invasive fish such as the eastern mosquitofish, Gambusia holbrooki, have been implicated in the decline of amphibians, which suffer high extinction rates globally. Although G. holbrooki is one of the most studied freshwater fish, its diet shows wide geographic variation and its impact on amphibian populations remains unclear. Stable isotopes 13C and 15N were used in 10 urban ponds in Sydney, Australia to compare the diet of G. holbrooki in January, April and May 2013 using a stable isotope mixing model. Gambusia holbrooki was carnivorous and fed on invertebrates (24¿39%), tadpoles (25¿32%) and conspecifics (20¿45%). In contrast to previous studies, primary producers were a negligible part of Gambusia holbrooki diet (<10%). Its diet in late autumn comprised a high proportion of conspecifics (up to 45%) owing to the depletion of other food sources before winter (metamorphosis of larvae). This study provides evidence of high rates of predation on native tadpoles and invertebrates by a highly invasive fish. This knowledge should be incorporated into amphibian releases through head-starting tadpoles or using soft releases where tadpoles are placed in predator-free enclosures until larvae are large enough to avoid predation. Considering the dire conservation status of amphibians globally and the growing interest for invertebrates, it is suggested that stable isotopes are valuable to identify threats from predation in order to target conservation practice toward suitable priorities. Copyright © 2016 John Wiley & Sons, Ltd.

© 2015, National Research Council of Canada. All rights reserved. Despite the global distribution of sawsharks, little is known about their diets or their role in the marine biosphere. As species in higher trophic positions are generally considered to be more at risk to perturbations such as fishing, understanding their role in the food chain will enable better conservation and management strategies for these species. Two sawshark species (Pristiophorus cirratus, Pristiophorus nudipinnis) co-occur in waters off east Tasmania, Australia. This study determined the trophic positions of these sawsharks and whether they avoided competing with each other through resource partitioning. Isotopic analysis of muscle tissue revealed that P. cirratus and P. nudipinnis had significantly different trophic levels, with P. cirratus likely to have a diet of primary consumers and P. nudipinnis likely to have a piscivorous diet. Owing to their different isotopic signatures, it is also likely that the sawshark rostrum has multiple functions. Both species shifted to higher trophic levels during ontogeny. Maternal isotopic signatures were detectable in P. cirratus juveniles.

© 2014 John Wiley & Sons Ltd. Tiger flathead, Neoplatycephalus richardsoni (Castelnau), and sand flathead, Platycephalus bassensis Cuvier, are undifferentiated and managed with a common legal minimum length (LML). The Commonwealth Trawl Sector (CTS) and the Tasmanian Danish-seine fishery (TDSF) use a minimum codend mesh sizes of 90 and 70 mm, respectively. The codend mesh size should be tailored to the LML, which is based on the length of first maturity of females (M50). This study found the length-girth relationship of N. richardsoni and P. bassensis was not significantly different. Using the covered codend method, these two species had 50% retention lengths (L50) of 294 ± 2 and 307 ± 3 mm, in 70-mm and 90-mm codends, respectively. L50 estimates for mesh sizes from this study and others produced a curvilinear relationship: y = 120 ln(x) - 214, with an r2 of 0.8504. The size at maturity (M50) for female N. richardsoni was 337 mm, which is larger than the estimate for female P. bassensis (247 mm). There is a mismatch between the estimates of L50, the estimates of M50 and the LMLs in each fishery, leading to suboptimal exploitation of female Platycephalus. The model produced in this paper recommends a codend mesh size of 98 mm for both fisheries to exploit Platycephalus species sustainably.

This article describes the regulatory framework and assessment process of urban wastewater reuse in two distinct regions of Australia, the Tamar Valley in northern Tasmania and the Hunter region of New South Wales. Relative similarities are evident between human population, water availability and recent necessity for reuse feasibility assessments. In the Hunter, assessments informed a state government led catchment-scale water security strategy. In Launceston, the need for assessments stems from a condition of the environmental permits for individual facilities. Salient institutional, social, economic and political barriers mire the assessment process for, and success of, wastewater reuse. Distinct legal, policy and procedural differences exist between the two cases. Future reuse guidelines should identify the different drivers for wastewater reuse and avoid studies that meet administratively predetermined selection.