Recent publications in Science and Engineering
The forests of Borneo—the third largest island on the planet—sustain some of the highest biodiversity and carbon storage in the world. The forests also provide vital ecosystem services and livelihood support for millions of people in the region, including many indigenous communities. The Pan-Borneo Highway and several hydroelectric dams are planned or already under construction in Sarawak, a Malaysian state comprising part of the Borneo. This development seeks to enhance economic growth and regional connectivity, support community access to services, and promote industrial development. However, the implications of the development of highway and dams for forest integrity, biodiversity and ecosystem services remained largely unreported. We assessed these development projects using fine-scale biophysical and environmental data and found several environmental and socioeconomic risks associated with the projects. The highway and hydroelectric dam projects will impact 32 protected areas including numerous key habitats of threatened species such as the proboscis monkey (Nasalis larvatus), Sarawak surili (Presbytis chrysomelas), Bornean orangutans (Pongo pygmaeus) and tufted ground squirrel (Rheithrosciurus macrotis). Under its slated development trajectory, the local and trans-national forest connectivity between Malaysian Borneo and Indonesian Borneo would also be substantially diminished. Nearly ~161 km of the Pan-Borneo Highway in Sarawak will traverse forested landscapes and ~55 km will traverse carbon-rich peatlands. The 13 hydroelectric dam projects will collectively impact ~1.7 million ha of forest in Sarawak. The consequences of planned highway and hydroelectric dams construction will increase the carbon footprint of development in the region. Moreover, many new road segments and hydroelectric dams would be built on steep slopes in high-rainfall zones and forested areas, increasing both construction and ongoing maintenance costs. The projects would also alter livelihood activities of downstream communities, risking their long-term sustainability. Overall, our findings identify major economic, social and environmental risks for several planned road segments in Sarawak—such as those between Telok Melano and Kuching; Sibu and Bintulu; and in the Lambir, Limbang and Lawas regions—and dam projects—such as Tutoh, Limbang, Lawas, Baram, Linau, Ulu Air and Baleh dams. Such projects need to be reviewed to ensure they reflect Borneo’s unique environmental and forest ecosystem values, the aspirations of local communities and long-term sustainability of the projects rather than being assessed solely on their short term economic returns.
Nordborg, F. Mikaela, Jones, Ross J., Oelgemöller, Michael, and Negri, Andrew P. (2020) The effects of ultraviolet radiation and climate on oil toxicity to coral reef organisms – a review. Science of the Total Environment, 720. 137486.
Oil pollution remains a significant local threat to shallow tropical coral reef environments, but the environmental conditions typical of coral reefs are rarely considered in oil toxicity testing and risk assessments. Here we review the effects of three environmental co-factors on petroleum oil toxicity towards coral reef organisms, and show that the impacts of oil pollution on coral reef taxa can be exacerbated by environmental conditions commonly encountered in tropical reef environments. Shallow reefs are routinely exposed to high levels of ultraviolet radiation (UVR), which can substantially increase the toxicity of some oil components through phototoxicity. Exposure to UVR represents the most likely and harmful environmental co-factor reviewed here, leading to an average toxicity increase of 7.2-fold across all tests reviewed. The clear relevance of UVR co-exposure and its strong influence on tropical reef oil toxicity highlights the need to account for UVR as a standard practice in future oil toxicity studies. Indeed, quantifying the influence of UVR on toxic thresholds of oil to coral reef species is essential to develop credible oil spill risk models required for oil extraction developments, shipping management and spill responses in the tropics. The few studies available indicate that co-exposure to elevated temperature and low pH, both within the range of current daily and seasonal fluctuations and/or projected under continued climate change, can increase oil toxicity on average by 3.0- and 1.3-fold, respectively. While all three of the reviewed environmental co-factors have the potential to substantially increase the impacts of oil pollution in shallow reef environments, their simultaneous effects have not been investigated. Assessments of the combined effects of oil pollution, UVR, temperature and low pH will become increasingly important to identify realistic hazard thresholds suitable for future risk assessments over the coming century.
Munksgaard, Niels C., Zwart, Costijn, Haig, Jordahna, Cernusak, Lucas A., and Bird, Michael I. (2020) Coupled rainfall and water vapour stable isotope time series reveal tropical atmospheric processes on multiple timescales. Hydrological Processes, 34 (1). pp. 111-124.
High-frequency stable isotope data are useful for validating atmospheric moisture circulation models and provide improved understanding of the mechanisms controlling isotopic compositions in tropical rainfall. Here, we present a near-continuous 6-month record of O- and H-isotope compositions in both water vapour and daily rainfall from Northeast Australia measured by laser spectroscopy. The data set spans both wet and dry seasons to help address a significant data and knowledge gap in the southern hemisphere tropics. We interpret the isotopic records for water vapour and rainfall in the context of contemporaneous meteorological observations. Surface air moisture provided near-continuous tracking of the links between isotopic variations and meteorological events on local to regional spatial scales. Power spectrum analysis of the isotopic variation showed a range of significant periodicities, from hourly to monthly scales, and cross-wavelet analysis identified significant regions of common power for hourly averaged water vapour isotopic composition and relative humidity, wind direction, and solar radiation. Relative humidity had the greatest subdiurnal influence on isotopic composition. On longer timescales (weeks to months), isotope variability was strongly correlated with both wind direction and relative humidity. The high-frequency records showed diurnal isotopic variations in O- and H-isotope compositions due to local dew formation and, for deuterium excess, as a result of evapotranspiration. Several significant negative isotope anomalies on a daily scale were associated with the activity of regional mesoscale convective systems and the occurrence of two tropical cyclones. Calculated air parcel back trajectories identified the predominant moisture transport paths from the Southwest Pacific Ocean, whereas moisture transport from northerly directions occurred mainly during the wet season monsoonal airflow. Water vapour isotope compositions reflected the same meteorological events as recorded in rainfall isotopes but provided much more detailed and continuous information on atmospheric moisture cycling than the intermittent isotopic record provided by rainfall. Improved global coverage of stable isotope data for atmospheric water vapour is likely to improve simulations of future changes to climate drivers of the hydrological cycle.
Noble, Tansyn N., Coman, Gregory J., Wade, Nicholas M., Thomson, Peter C., Raadsma, Herman W., Khatkar, Mehar S., Guppy, Jarrod L., and Jerry, Dean R. (2020) Genetic parameters for tolerance to gill-associated virus under challenge-test conditions in the black tiger shrimp (Penaeus monodon). Aquaculture, 516. 734428.
Diseases in shrimp aquaculture cause significant economic losses, particularly those caused by viruses. Genetic improvement of disease tolerance through selective breeding can be an important tool for managing the risk of disease in shrimp farming as long as the trait has a genetic basis (i.e. heritable) and is able to be accurately and reliably measured. This study presents the first estimates of genetic variation associated with tolerance to gill-associated virus (GAV) in Penaeus monodon using a unique controlled challenge test design. Shrimp families (n = 72) were communally spawned and reared prior to replicated communal challenge testing when they reached an average size of ~8 g. Pedigree determination was carried out using genotyping and shrimp were challenged by intramuscular injection with a weight standardised dose of GAV. Daily mortality data were collected over 15 days from 1717 individuals and GAV infection load was measured on the challenge test survivors (n = 963). Overall mortality after 15 days was 35.5% and ranged from 0 to 71% among families. Heritability estimates for mortality were 0.11 ± 0.03 using a binomial model and 0.14 (standard error not estimated) using Cox's proportional hazards model. The estimated heritability for GAV infection load was 0.21 ± 0.07. The genetic correlation between mortality and GAV infection load was not significantly different from zero, rg = 0.30 ± 0.23, suggesting that the two traits may be genetically independent, at least in the way they were measured in this study. Results from this study suggest a low but significant genetic basis for GAV tolerance in P. monodon and that selection may be a viable option to manage GAV-related disease. The study also demonstrated, for the first time in shrimp, communal-based spawning and rearing can be used for large-scale genetic analysis of disease tolerance, eliminating the need for single family rearing tanks and associated confounding environmental effects.
Quesada, Carlos Alberto, Paz, Claudia, Mendoza, Erick Oblitas, Phillips, Oliver Lawrence, Saiz, Gustavo, and Lloyd, Jon (2020) Variations in soil chemical and physical properties explain basin-wide Amazon forest soil carbon concentrations. Soil, 6 (1). pp. 53-88.
We investigate the edaphic, mineralogical and climatic controls of soil organic carbon (SOC) concentration utilising data from 147 primary forest soils (0-30 cm depth) sampled in eight different countries across the Amazon Basin. Sampled across 14 different World Reference Base soil groups, our data suggest that stabilisation mechanism varies with pedogenetic level. Specifically, although SOC concentrations in Ferralsols and Acrisols were best explained by simple variations in clay content - this presumably being due to their relatively uniform kaolinitic mineralogy - this was not the case for less weathered soils such as Alisols, Cambisols and Plinthosols for which interactions between Al species, soil pH and litter quality are argued to be much more important. Although for more strongly weathered soils the majority of SOC is located within the aggregate fraction, for the less weathered soils most of the SOC is located within the silt and clay fractions. It thus seems that for highly weathered soils SOC storage is mostly influenced by surface area variations arising from clay content, with physical protection inside aggregates rendering an additional level of protection against decomposition. On the other hand, most of the SOC in less weathered soils is associated with the precipitation of aluminium-carbon complexes within the fine soil fraction, with this mechanism enhanced by the presence of high levels of aromatic, carboxyl-rich organic matter compounds. Also examined as part of this study were a relatively small number of arenic soils (viz. Arenosols and Podzols) for which there was a small but significant influence of clay and silt content variations on SOM storage, with fractionation studies showing that particulate organic matter may account for up to 0.60 of arenic soil SOC. In contrast to what were in all cases strong influences of soil and/or litter quality properties, after accounting for these effects neither wood productivity, above-ground biomass nor precipitation/temperature variations were found to exert any significant influence on SOC stocks. These results have important implications for our understanding of how Amazon forest soils are likely to respond to ongoing and future climate changes.
Wang, Yong, Tang, Juxing, Wang, Liqiang, Huizenga, Jan Marten, Santosh, M., Zheng, Silun, Hu, Yu, and Gao, Teng (2020) Geology, geochronology and geochemistry of the Miocene Jiaoxi quartz vein-type W deposit in the western part of the Lhasa Terrane, Tibet: implications for ore genesis. Ore Geology Reviews, 120. 103433.
The Jiaoxi deposit is the first Miocene quartz vein-type W deposit discovered in the western part of the Lhasa Terrane comprising with 39,000 metric tons of WO3. The mineralization occurs in wolframite-bearing hydrothermal tensional quartz veins and is associated with Miocene granites. The mineralization event can be divided into an early quartz-oxide stage succeeded by a sulfide stage, and a final fluorite-carbonate stage. Magmatic intrusions at the deposit include biotite monzogranite porphyry, biotite monzogranite, granite porphyry, and muscovite granite at depth and show crystallization ages ranging between 14.5 and 13.7 Ma. Whole-rock geochemistry shows that the intrusions are alkali-rich peraluminous granites that experienced strong fractional crystallization. The most evolved muscovite granite has high W, Nb and Cs contents and is considered to be the source for mineralization. During the late crystallization stage of the highly fractionated muscovite granite, exsolved hydrothermal fluids interacted with the muscovite granite magma and migrated along extensional fractures forming the Jiaoxi deposit. Zircon grains from the granites show uniform εHf (t) values with a wide range between −7.08 and +3.87. The granites have initial Sr isotopic compositions ranging between 0.7094 and 0.7124 and negative εNd (t) values ranging between −4.9 and −9.4. The Sr-Nd-Hf isotope data indicate that the granites were derived from partial melting of a crustal source with minor contributions from the lithospheric mantle. The 3He/4He ratios for wolframite and pyrite vary between 0.30 and 0.74 Ra (Ra = 1.4 × 10–6 for air), confirming that W was mainly sourced from the crust. Collectively, the regional geology, geochronology and geochemistry, indicate that the Miocene post-collisional peraluminous granites and associated W mineralization were triggered by the roll-back and gradual break-off of the northward-subducting Indian continental lithosphere slab. The less evolved biotite monzogranite porphyry, which contains ore-bearing veins and local greisen alteration, appears to be unrelated to W mineralization.
Liu, Guangxian, Yuan, Feng, Deng, Yufeng, Wang, Fangyue, White, Noel, Huizenga, Jan, Li, Yue, Li, Xiaohui, and Zhou, Taofa (2020) Ore-fluid geochemistry of the Hehuashan Pb–Zn deposit in the Tongling ore district, Anhui province, China: evidence from REE and C–H–O isotopes of calcite. Ore Geology Reviews, 117. 103279.
Calcite is the main gangue mineral of the Hehuashan lead–zinc deposit, which is located in the Tongling ore district, Anhui Province, East China. The ore bodies of the Hehuashan deposit are hosted by dissolution breccia of the Lower Triassic carbonate sediments. We report petrography, rare earth elements (REE), and C–H–O isotope data of four generations of calcite recognized in the Hehuashan deposit, namely the pre-ore stage calcite (Cal-1), early ore-forming stage calcite (Cal-2), late ore-forming stage calcite (Cal-3) and post-ore stage calcite (Cal-4). In addition, we also report C–H–O isotopes data of dolostone from the Lower Triassic carbonate sediments. All four calcite generations show a low ∑REE content (13–50 ppm on average), indicating that the related ore-forming fluids may not have been derived a magmatic fluid but rather be derived from the carbonate sediments or basinal brines. Low LREE/HREE ratio (1.1–6.1 on average) of all four calcite generations implies that no significant REE fractionation happened during the mineralizing processes. The wide distribution of Y/Ho ratios (17–70) of calcite indicates a result of fluids mixing. The δ¹³C values of calcite (1.4‰ to 4.2‰) are comparable to marine carbonates, but the δ¹⁸O values are lower, indicating possibly a result of carbonates dissolution. Calculated δ¹⁸O of the fluid in equilibrium with calcite vary from –3.1‰ to –0.1‰, combining the δDV-SMOW (–100‰ to –81‰), implying a fluid mixing of a brine fluid and meteoric water or diagenetic pore water for the mineralization of the Hehuashan deposit.
Orr, Ryan, Hocking, Rosalie K., Pattison, Anthony, and Nelson, Paul N. (2020) Extraction of metals from mildly acidic tropical soils: interactions between chelating ligand, pH and soil type. Chemosphere, 248. 126060.
Naturally occurring and synthetic chelating ligands can act as suppressants for fungal pathogens, nematodes and weeds, based on their ability to alter micronutrient bioavailability in soil, particularly iron. Chelators are also used as detergents, for remediation of heavy metal contamination and for supplying metals as fertiliser. The aim of this work was to test the ability of chelators to solubilise metals, in particular iron, in tropical soils over an environmentally relevant pH range. Six topsoils from farms in North Queensland, Australia were adjusted to pH 5, 6 and 7 and then extracted with CaCl2, EDTA, DTPA, EDDHA and mimosine. The extracts were analysed for concentrations of aluminium, copper, iron, magnesium, manganese, potassium, strontium and zinc. EDDHA solubilised iron effectively under all of the conditions tested, indicating its likely suitability for pest suppression. The concentration of aluminium in EDDHA extracts was positively correlated with pH, and at pH 7 the concentration of aluminium was far greater than that of iron. An increase in the mobility of aluminium from EDDHA application to soil may lead to aluminium toxicity in plants, which should be considered further in any practical application of EDDHA. Mimosine, which is also a strong chelator, was a poor extractor of all metals, possibly due to adsorption to the soil.
Pillai, Rishab, Nordberg, Eric, Riedel, Jendrian, and Schwarzkopf, Lin (2020) Nonlinear variation in clinging performance with surface roughness in geckos. Ecology and Evolution. (In Press)
Understanding the challenges faced by organisms moving within their environment is essential to comprehending the evolution of locomotor morphology and habitat use. Geckos have developed adhesive toe pads that enable exploitation of a wide range of microhabitats. These toe pads, and their adhesive mechanisms, have typically been studied using a range of artificial substrates, usually significantly smoother than those available in nature. Although these studies have been fundamental in understanding the mechanisms of attachment in geckos, it is unclear whether gecko attachment simply gradually declines with increased roughness as some researchers have suggested, or whether the interaction between the gekkotan adhesive system and surface roughness produces nonlinear relationships. To understand ecological challenges faced in their natural habitats, it is essential to use test surfaces that are more like surfaces used by geckos in nature. We tested gecko shear force (i.e., frictional force) generation as a measure of clinging performance on three artificial substrates. We selected substrates that exhibit microtopographies with peak-to-valley heights similar to those of substrates used in nature, to investigate performance on a range of smooth surfaces (glass), and fine-grained (fine sandpaper) to rough (coarse sandpaper). We found that shear force did not decline monotonically with roughness, but varied nonlinearly among substrates. Clinging performance was greater on glass and coarse sandpaper than on fine sandpaper, and clinging performance was not significantly different between glass and coarse sandpaper. Our results demonstrate that performance on different substrates varies, probably depending on the underlying mechanisms of the adhesive apparatus in geckos.
Humphreys, M.T., Ginger, J.D., and Henderson, D.J. (2020) Effect of opening size and wind speed on internal pressures in full-scale buildings. In: Lecture Notes in Civil Engineering (37) pp. 1061-1069. From: ACMSM25: 25th Australasian Conference on Mechanics of Structures and Materials, 4-7 December 2018, Brisbane, QLD, Australia.
Internal pressures contribute to a significant proportion of the net pressure across a building envelope, which needs to be accurately defined in wind loading standards to optimize structural design. Current quasi-steady criteria for internal pressures in AS/NZS1170.2(2011) is dependent on the ratio of open area on the windward wall to leeward and sidewalls, with no consideration of dynamic (i.e. inertial and damping) effects. This paper shows that the internal to external pressure fluctuation relationship is a function of the opening area to volume parameter, S*=(A^(3/2)/V)(as /U_h^2) and opening area to integral length scale of turbulence parameter, Φ5=(λu /√A). Simple quasi-steady analysis used in AS/NZS1170.2(2011) suggests internal pressure should be equal to the external pressure applied to the opening, however, results here show Cases where peak internal pressures are greater than, equal to and less than the peak external pressure. This is caused by internal pressure resonance and/or damping shown to be a function of S* and Φ_5.
Jones, K., Burgess, G., Budd, A.M., Huerlimann, R., Mashkour, N., and Ariel, E. (2020) Molecular evidence for horizontal transmission of chelonid alphaherpesvirus 5 at green turtle (Chelonia mydas) foraging grounds in Queensland, Australia. PLoS ONE, 15 (1). e0227268.
Fibropapillomatosis (FP) is a marine turtle disease recognised by benign tumours on the skin, eyes, shell, oral cavity and/or viscera. Despite being a globally distributed disease that affects an endangered species, research on FP and its likely causative agent chelonid alphaherpesvirus 5 (ChHV5) in Australia is limited. Here we present improved molecular assays developed for detection of ChHV5, in combination with a robust molecular and phylogenetic analysis of ChHV5 variants. This approach utilised a multi-gene assay to detect ChHV5 in all FP tumors sampled from 62 marine turtles found at six foraging grounds along the Great Barrier Reef. Six distinct variants of ChHV5 were identified and the distribution of these variants was associated with host foraging ground. Conversely, no association between host genetic origin and ChHV5 viral variant was found. Together this evidence supports the hypothesis that marine turtles undergo horizontal transmission of ChHV5 at foraging grounds and are unlikely to be contracting the disease at rookeries, either during mating or vertically from parent to offspring.
Anderson, R Charles, Herrera, Miguel, Ilangakoon, Anoukchika D., Koya, K.M., Moazzam, M., Mustika, Putu L., and Sutaria, Dipani N. (2020) Cetacean bycatch in Indian Ocean tuna gillnet fisheries. Endangered Species Research, 41. pp. 39-53.
Pelagic gillnet (driftnet) fisheries account for some 34% of Indian Ocean tuna catches. We combined published results from 10 bycatch sampling programmes (1981−2016) in Australia, Sri Lanka, India and Pakistan to estimate bycatch rates for cetaceans across all Indian Ocean tuna gillnet fisheries. Estimated cetacean bycatch peaked at almost 100 000 ind. yr−1 during 2004−2006, but has declined by over 15% since then, despite an increase in tuna gillnet fishing effort. These fisheries caught an estimated cumulative total of 4.1 million small cetaceans between 1950 and 2018. These bycatch estimates take little or no account of cetaceans caught by gillnet but not landed, of delayed mortality or sub-lethal impacts on cetaceans (especially whales) that escape from gillnets, of mortality associated with ghost nets, of harpoon catches made from gillnetters, or of mortality from other tuna fisheries. Total cetacean mortality from Indian Ocean tuna fisheries may therefore be substantially higher than estimated here. Declining cetacean bycatch rates suggest that such levels of mortality are not sustainable. Indeed, mean small cetacean abundance may currently be 13% of pre-fishery levels. None of these estimates are precise, but they do demonstrate the likely order of magnitude of the issue. Countries with the largest current gillnet catches of tuna, and thus the ones likely to have the largest cetacean bycatch are (in order): Iran, Indonesia, India, Sri Lanka, Pakistan, Oman, Yemen, UAE and Tanzania. These 9 countries together may account for roughly 96% of all cetacean bycatch from tuna gillnet fisheries across the Indian Ocean.
Barton, Jonathan A., Humphrey, Craig, Bourne, David G., and Hutson, Kate S. (2020) Biological controls to manage Acropora-eating flatworms in coral aquaculture. Aquaculture Environment Interactions, 12. pp. 61-66.
Coral aquaculture is expanding to supply the marine ornamental trade and active coral reef restoration. A common pest of Acropora corals is the Acropora-eating flatworm Prosthiostomum acroporae, which can cause colonial mortality at high infestation densities on Acropora spp. We investigated the potential of 2 biological control organisms in marine aquaria for the control of P. acroporae infestations. A. millepora fragments infested with adult polyclad flatworms (5 flatworms fragment(-1)) or single egg clusters laid on Acropora skeleton were cohabited with either sixline wrasse Pseudocheilinus hexataenia or the peppermint shrimp Lysmata vittata and compared to a control (i.e. no predator) to assess their ability to consume P. acroporae at different life stages over 24 h. P. hexataenia consumed 100% of adult flatworms from A. millepora fragments (n = 9; 5 flatworms fragment(-1)), while L. vittata consumed 82.0 +/- 26.36% of adult flatworms (mean +/- SD; n= 20). Pseudocheilinus hexataenia did not consume any Prosthiostomum acroporae egg capsules, while L. vittata consumed 63.67 +/- 43.48% (n = 20) of egg capsules on the Acropora skeletons. Mean handling losses in controls were 5.83% (shrimp system) and 3.50% (fish system) of flatworms and 2.39% (fish system) and 3.50% (shrimp system) of egg capsules. Encounters between L. vittata and P. hexataenia result in predation of P. acroporae on an Acropora coral host and represent viable biological controls for reducing infestations of P. acroporae in aquaculture systems.
Taylor, Brett M., Benkwitt, Cassandra E., Choat, Howard, Clements, Kendall D., Graham, Nicholas A.J., and Meekan, Mark G. (2020) Synchronous biological feedbacks in parrotfishes associated with pantropical coral bleaching. Global Change Biology, 26 (3). pp. 1285-1294.
Biological feedbacks generated through patterns of disturbance are vital for sustaining ecosystem states. Recent ocean warming and thermal anomalies have caused pantropical episodes of coral bleaching, which has led to widespread coral mortality and a range of subsequent effects on coral reef communities. Although the response of many reef-associated fishes to major disturbance events on coral reefs is negative (e.g., reduced abundance and condition), parrotfishes show strong feedbacks after disturbance to living reef structure manifesting as increases in abundance. However, the mechanisms underlying this response are poorly understood. Using biochronological reconstructions of annual otolith (ear stone) growth from two ocean basins, we tested whether parrotfish growth was enhanced following bleaching-related coral mortality, thus providing an organismal mechanism for demographic changes in populations. Both major feeding guilds of parrotfishes (scrapers and excavators) exhibited enhanced growth of individuals after bleaching that was decoupled from expected thermal performance, a pattern that was not evident in other reef fish taxa from the same environment. These results provide evidence for a more nuanced ecological feedback system-one where disturbance plays a key role in mediating parrotfish-benthos interactions. By influencing the biology of assemblages, disturbance can thereby stimulate change in parrotfish grazing intensity and ultimately reef geomorphology over time. This feedback cycle operated historically at within-reef scales; however, our results demonstrate that the scale, magnitude, and severity of recent thermal events are entraining the biological responses of disparate communities to respond in synchrony. This may fundamentally alter feedbacks in the relationships between parrotfishes and reef systems.
Mbaru, Emmanuel K., Graham, Nicholas A.J., McClanahan, Timothy R., and Cinner, Joshua E. (2020) Functional traits illuminate the selective impacts of different fishing gears on coral reefs. Journal of Applied Ecology. (In Press)
Unsustainable fishing is a major driver of change in marine ecosystems. The ways that fishing gears target fishes with different ecological functions are unclear, particularly in complex multispecies fisheries. Here, we examine whether artisanal fishing gears selectively target fishes with unique combinations of ecological traits (diet, body size, depth, position in water column, period of activity, schooling behaviour) in a coral reef ecosystem. We use coral reef fish landing data from 25 sites along the Kenyan coast collected over a 7-year period. All fishing gears targeted a wide diversity of traits, but with some differentiation among gears. Fish assemblages captured by spearguns were significantly different from the other gear types, specializing on diurnal species that feed on sessile invertivores. Nets, including gillnets and beachseines, targeted the most functional diversity. Escape slot traps targeted the least functionally diverse assemblages. Basket traps and escape slot traps targeted the most functionally similar species of all two-gear combinations. There were 163 functional entities (unique combinations of traits) captured in the fishery; however, 50% of the catch by each gear was from only two to six functional entities. Most of the differences in gear selectivity were due to unique and rarely targeted functional entities, that made up only a small proportion of the catch. Synthesis and applications. Coral reef fisheries target a breadth of functional entities (unique combinations of traits), but catches are heavily skewed towards relatively few functional entities. While banning specific gears will benefit rare functional entities in the catch, effort reductions will be necessary to alleviate pressure on commonly targeted functional entities.
Noordin, Noordiyana M., Zeng, Chaoshu, and Southgate, Paul C. (2020) Survival, molting pattern, and growth of early blue swimmer crab, Portunus pelagicus, juveniles fed diets containing varying levels of cholesterol. Journal of the World Aquaculture Society, 51. pp. 255-265.
This study examined the effects of dietary cholesterol on the survival, molting pattern, and growth of early juveniles of the blue swimmer crab, Portunus pelagicus. Seven isocaloric diets were formulated to contain cholesterol at 0 (basal diet), 2.5, 5.0, 7.5, 10, 12.5, and 15 g/kg diet dry weight. Survival ranged from 20 to 47.5%, with the highest survival recorded for crabs fed the diet supplemented with 10 g/kg cholesterol, while the lowest survival was demonstrated by crabs fed the basal diet. The highest occurrence of molt death syndrome was found for crabs fed the diet with cholesterol supplementation of 15 g/kg. A general trend of decreasing development time to the crab 3 (C3) stage was observed with increasing dietary cholesterol supplementation up to a level of 10 g/kg, but this then decreased as dietary cholesterol level was increased to 12.5 and 15 g/kg. The specific growth rates of crabs, calculated for dry weight, carapace width, and carapace length, followed a similar trend. Our results suggest that, under the current feeding conditions, a dietary cholesterol level of 10 g/kg appears to be optimal for the culture of early juveniles of P. pelagicus.
White, William T., Baje, Leontine, Appleyard, Sharon A., Chin, Andrew, Smart, Jonathan J., and Simpfendorfer, Colin A. (2020) Shark longline fishery of Papua New Guinea: size and species composition and spatial variation of the catches. Marine and Freshwater Research. (In Press)
This study provides the first detailed investigation of the catches of the shark longline fishery in Papua New Guinea. Fisheries observers collected data on shark catches from a total of 318 longline sets between May and June 2014, before its closure in July 2014. In all, 14 694 sharks were recorded with a total estimated biomass of 439 tonnes (Mg). Eighteen species of sharks were recorded in the observer data, with the most dominant species being Carcharhinus falciformis, which constituted more than 90% of the total catches by both weight and number of individuals. The level of observer misidentification was low (<10%), which reflected the use of region-specific identification guides by well-trained fisheries observers. The most diverse catches were in the Solomon Sea area, whereas catches in most other areas, particularly the Bismarck Sea areas, were less diverse and more strongly dominated by C. falciformis. Size and sex ratios varied by species, highlighting the importance of obtaining species-level information from the fishery being investigated. Any consideration by fisheries managers to reopen this fishery needs to consider the effect this will have on the species targeted and the livelihoods of coastal fishers who also rely on the same resources.
Henderson, Christopher J., Gilby, Ben L., Schlacher, Thomas A., Connolly, Rod M., Sheaves, Marcus, Maxwell, Paul S., Flint, Nicole, Borland, Hayden P., Martin, Tyson S.H., Gorissen, Bob, and Olds, Andrew D. (2020) Landscape transformation alters functional diversity in coastal seascapes. Ecography, 43 (1). pp. 138-148.
The ecological impacts of landscape modification and urbanisation have transformed the composition of plant and animal assemblages, and altered the condition of ecosystems globally. Landscape transformation influences the spatial distribution of species and ecological functions by selecting for generalist species with wide ecological niches, which can adapt to opportunities in highly-modified environments. These effects of landscape modification can shape functional diversity on land, but it is not clear whether they have similar functional consequences in the sea. We used estuaries as a model system to test how landscape transformation alters functional diversity in coastal seascapes, and measured how variation in level of urbanisation, catchment modification and habitat loss influenced fish diversity across thirty-nine estuaries in eastern Australia. Fish were surveyed with baited remote underwater video stations and functional diversity was indexed with three metrics that describe variation in the functional traits and niche space of assemblages. The extent of landscape transformation in the catchment of each estuary was associated with variation in the functional diversity of estuarine fish assemblages. These effects were, however, not what we expected as functional diversity was highest in modified estuaries that supported a large area of both urban and grazing land in their catchments, were bordered by a small area of natural terrestrial vegetation and that contained a moderate area of mangroves. Zoobenthivores and omnivores dominated assemblages in highly-modified estuaries, and piscivorous fishes were common in natural waterways. Our results demonstrate, that the modification and urbanisation of ecosystems on land can alter functional diversity in the sea. Intense landscape transformation appears to select for abundant generalists with wide trophic niches, and against species with specialised diets, and we suggest that these changes might have fundamental consequences for ecosystem functioning in estuaries, and other highly modified seascapes.
Armstrong, Amelia J., Armstrong, Asia O., Bennett, Michael B., McGregor, Frazer, Abrantes, Kátya G., Barnett, Adam, Richardson, Anthony J., Townsend, Kathy A., and Dudgeon, Christine L. (2020) The geographic distribution of reef and oceanic manta rays (Mobula alfredi and Mobula birostris) in Australian coastal waters. Journal of Fish Biology. (In Press)
The known distribution of manta rays in Australian waters is patchy, with records primarily centred around tourism hotspots. We collated 11,614 records of Mobula alfredi from photo-ID databases (n = 10,715), aerial surveys (n = 378) and online reports (n = 521). The study confirms an uninterrupted coastal distribution from north of 26 degrees S and 31 degrees S on the west and east coasts, respectively. More southerly M. alfredi records relate to warm-water events with a southernmost extent at 34 degrees S. Coastal sightings of Mobula birostris were rare (n = 32), likely reflecting a preference for offshore waters, but encompass a wider latitudinal extent than M. alfredi of 10-40 degrees S.
Buddle, Alice L., Otway, Nicholas M., Van Dyke, James U., Thompson, Michael B., Murphy, Christopher R., Dowland, Samson N., Simpfendorfer, Colin A., Ellis, Megan T., and Whittington, Camilla M. (2020) Structural changes to the uterus of the dwarf ornate wobbegong shark (Orectolobus ornatus) during pregnancy. Journal of Morphology. (In Press)
Embryos of the viviparous dwarf ornate wobbegong shark (Orectolobus ornatus) develop without a placenta, unattached to the uterine wall of their mother. Here, we present the first light microscopy study of the uterus of O. ornatus throughout pregnancy. At the beginning of pregnancy, the uterine luminal epithelium and underlying connective tissue become folded to form uterine ridges. By mid to late pregnancy, the luminal surface is extensively folded and long luminal uterine villi are abundant. Compared to the nonpregnant uterus, uterine vasculature is increased during pregnancy. Additionally, as pregnancy progresses the uterine epithelium is attenuated so that there is minimal uterine tissue separating large maternal blood vessels from the fluid that surrounds developing embryos. We conclude that the uterus of O. ornatus undergoes an extensive morphological transformation during pregnancy. These uterine modifications likely support developing embryos via embryonic respiratory gas exchange, waste removal, water balance, and mineral transfer.
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