Search

Crabs can be transported beyond their native range via anthropogenic-mediated means such as aquarium trade, live seafood trade and shipping. Once introduced into new locations, they can establish persisting populations and become invasive, often leading to negative impacts on the recipient environment and native species. Molecular techniques are increasingly being used as complementary tools in biosecurity surveillance and monitoring plans for invasive species. Molecular tools can be particularly useful for early detection, rapid identification and discrimination of closely related species, including when diagnostic morphological characters are absent or challenging, such as early life stages, or when only part of the animal is available. In this study, we developed a species-specific qPCR assay, which targets the cytochrome c oxidase subunit 1 (CO1) region of the Asian paddle crab Charybdis japonica. In Australia, as well as many parts of the world, this species is considered invasive and routine biosecurity surveillance is conducted to reduce the risk of establishment. Through rigorous testing of tissue from target and non-target species we demonstrate that this assay is sensitive enough to detect as little as two copies per reaction and does not cross amplify with other closely related species. Field samples and environmental samples spiked with C. japonica DNA in high and low concentrations indicate that this assay is also a promising tool for detecting trace amounts of C. japonica eDNA in complex substrates, making it a useful complementary tool in marine biosecurity assessments. [ABSTRACT FROM AUTHOR]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jenvman.2005.08.021 Byline: Justin I. McDonald, Grey T. Coupland, Gary A. Kendrick Abstract: To date seagrass monitoring has involved the removal of seagrass from its environment. In fragile or highly disturbed systems, monitoring using destructive techniques may interfere with the environment or add to the burden of disturbance. Video photography is a form of non-destructive monitoring that does not require the removal of seagrass or interference with the environment and has the potential to be a valuable tool in monitoring seagrass systems. This study investigated the efficacy of video photography as a tool for detecting change in seagrass cover, using the temperate Australian species Amphibolis antarctica (Labill.) Sonder ex Aschers. Using visual and random point estimates of seagrass cover from video footage, it was possible to determine the minimum sample size (number of random video frames) needed to detect change in seagrass cover, the minimum detectable change in cover and the probability of the monitoring design committing a Type II error. Video footage was examined at three scales: transects (m apart), sites (km apart) and regions (tens of km apart). Using visual and random point estimation techniques, a minimum sample size of ten quadrats per transect was required to detect change in uniform and variable seagrass cover. With ten quadrats it was possible to identify a minimum detectable change in cover of 15% for uniform and 30% for variable seagrass cover. Power analysis was used to determine the probability of committing a Type II error from the data. Region level data had low power, corresponding to a high risk of committing a Type II error. Site and transect level data had high power corresponding to a low risk of committing a Type II error. Based on this study's data, managers using video to monitor for change in seagrass cover are advised to use data from the smaller scale, for example, site and transect level data. By using data from the smaller scale, managers will have a low risk of incorrectly concluding there has not been a disturbance when one has actually occurred. Author Affiliation: Faculty of Natural and Agricultural Sciences, School of Plant Biology M090, University of Western Australia, 35 Stirling Highway, Crawley 6009, Western Australia Article History: Received 16 April 2003; Revised 23 August 2005; Accepted 26 August 2005

Anthropogenic agents of ocean change such as biological invasions, overfishing, habitat destruction, pollution and ocean acidification and warming are known to have a dramatic impact on marine ecosystems worldwide. They are also intrinsically connected. In Western Australia, a "hot-plate" settlement panel system aimed at investigating the effect of ocean warming on fouling communities led to the first report of a notorious worldwide invasive ascidian species Didemnum perlucidum. This species was subsequently recorded from numerous locations along the coast and included in the Western Australia Prevention List for Introduced Marine Pests. In the present study we used microsatellite markers to determine whether these populations are the result of single or multiple introductions to Australia and if anthropogenic vectors might have facilitated its spread. By including samples collected worldwide, we further aimed to evaluate broad-scale patterns of variation and ascertain whether regional differences could be used to determine the source of introductions of D. perlucidum to Australia. Our results report an extended geographic range for D. perlucidum in Australia and worldwide, in what is the most comprehensive genetic study of this species. Our data further supports the introduced status of D. perlucidum in Australia, an introduction that our results suggest having occurred most likely as a result of multiple events with subsequent admixture. The similarity between genotypes at locations in Western Australia suggests that domestic transport plays a crucial role in shaping these populations, most likely enhanced by climatic anomalies such as heat waves. The identification of the D. perlucidum native range and sourcing of international samples from potential sites of introduction to Australia, particularly south-east Asia, remains essential to understand the presence of this species in the country. Nevertheless, during this study we were able to increase our understanding of D. perlucidum populations in Western Australia. This work provides an important baseline for D. perlucidum management and protection of high value marine areas, in Australia and worldwide. [ABSTRACT FROM AUTHOR]

Numerous interceptions of Perna viridis on vessels entering Western Australian waters prompted the development of a rapid field-based assessment technique for determining reproductive status and hence spawning likelihood of P. viridis. The visual assessment tool and spawning likelihood matrix were developed using correlations between laboratory-based assessments of P. viridis size, colour and egg size in combination with field-based validations from mussels collected on vessels in Western Australian waters. The spawning likelihood matrix provides an immediate indicator of whether the mussel is low, medium or high likelihood of spawning. Mussels were recorded initiating gonad tissue development from approximately 6.5 mm in length, with the mean size of mature animals 59.6 mm. There was a positive correlation between mussel size and stage of reproductive development. Gonad colour, however, appeared to be a more accurate indicator of gonad maturity than mussel size. Female mussels showed a decrease in gonad colour intensity following spawning. Mussels that scored 1 for colour (potential score 1-3) generally had a low proportion of mature eggs (< 70% mature eggs). Over 60% of the mussels with a colour score of 2 contained 70-100% mature eggs, indicating the capacity for further spawning. Mussels were assigned an overall spawning likelihood score (through the spawning likelihood matrix) based on the proportion of the visceral mass occupied by gonad tissues (% gonad cover, value from 1-3) and overall colour of gonads (value from 1-3). The spawning likelihood score was significantly related to the percentage of mature eggs present, and hence the spawning potential of the mussel. The matrix provides an immediate indicator of the risk of spawning posed by the sample. As such, it is expected that application of the matrix in situ would enable the potential likelihood posed by P. viridis translocated on vessels to be determined quickly and efficiently. [ABSTRACT FROM AUTHOR]

The Asian green mussel Perna viridis is an abundant and important ecological and economical species across its native range. However, outside its native range, this species has been considered invasive and concerns have been raised worldwide regarding its potential impacts. Despite this, little work has been done to investigate the genetics of native and/or introduced populations of this species. In the present study, we developed 16 new polymorphic microsatellite markers using the Illumina MiSeq Platform. Four to 15 alleles per locus were detected. There was no evidence of linkage disequilibrium between pairs of loci and all loci were in Hardy-Weinberg equilibrium. [ABSTRACT FROM AUTHOR]

Didemnid species are assessed as species with a high invasive potential for Australia and as such are listed as target species for both state and national monitoring programs. The presence of the sea squirt Didemnum perlucidum (Monniot, 1983) was first documented in Australia in 2010 and has since then been detected extensively throughout the state of Western Australia and in the Northern Territory. These detections have raised important questions as to the origin and potential impact of this species in Australia. The current study was initiated to review the current known global geographic range of D. perlucidum and to obtain specimens that could support molecular studies aimed at evaluating the potential origin of this species in Australia. Characterization of 5' COI mitochondrial sequences from 286 specimens revealed a remarkably low level of genetic diversity across the current known range of D. perlucidum and the existence of one main widespread genetic haplotype. Such findings suggest that all locations sampled in this study may in fact represent introductions of D. perlucidum and that the natural native range of the species remains unknown. Our demonstration that specimens (n=187) originating from across a broad expanse of the Australian West Coast were comprised of a single haplotype also lends support to the hypothesis that D. perlucidum is a species that has been introduced recently into Australia. This hypothesis is supported by the fact that D. perlucium distribution in Australia is mostly confined to artificial structures, it has displayed invasive characteristics, and its presence is now being detected across an increasingly wide geographical area. Given the demonstrated low level of genetic COI variation across its known global distribution, lack of clarity around its native range, and limited availability of data on this species globally, we recognize the requirement for further work to more fully elucidate the exact origins and patterns of distribution of D. perlucidum in Australia. This study represents the most comprehensive mapping of the current global distribution of D. perlucidum conducted to date and will hopefully motivate further studies aimed at elucidating this species biology, origin, high-risk routes and impacts. [ABSTRACT FROM AUTHOR]

The Australian National System for the Prevention and Management of Introduced Marine Pest Incursions has identified seven Harmful Algal Bloom (HAB) toxic dinoflagellate species as target species of concern. Alexandrium minutum Halim, 1960, and Alexandrium cf. tamarense (Lebour) Balech, 1995, are currently known to occur in south-western estuaries and coastal waters but with no documented impact on the seafood industry or human health. Monitoring of these species is challenging, time-consuming, expensive, and often relies on traditional morphotaxonomy. This reports the first confirmed detection of another HAB species, Alexandrium catenella (Whedon and Kofoid) Balech, 1995, in Western Australia (WA), using both microscopic and molecular methods. The confirmed detection of A. catenella (A. pacificum Group IV genotype) in WA hopefully will motivate discussion about better monitoring and control of toxic HAB species. [ABSTRACT FROM AUTHOR]

The introduced crab, Charybdis japonica, was captured in the Swan River Estuary in Western Australia during October 2012. This constitutes the second documented report of this species in Western Australia after a single specimen was reported in 2010 from a nearby estuary. Given the invasive history of this species in locations such as New Zealand, a rapid-response delimiting survey was conducted to assess the prevalence of this crab within this estuary. A large public engagement campaign was run concurrently with the delimiting survey to inform and enlist the recreational crab fishers that use the Swan River and other nearby estuaries to report any more specimens that they caught. These activities yielded a total of three specimens, all handed in by recreational fishers as a result of the public engagement campaign. All three specimens were caught within a very limited area within the estuary, approximately 8 kilometres from the entrance. The two specimens that were able to be sexed were mature males, with carapace widths of 10.1 and 10.3 mm. The very small number of specimens caught, relative to the abundant native species indicates that C. japonica may be relatively scarce in the Swan River Estuary. This result highlights the importance of engaging members of the public to help detect introduced marine pest species in the early stages of incursions. [ABSTRACT FROM AUTHOR]

In 2010, the colonial ascidian Didemnum perlucidum (Monniot, 1983) was first recorded in Western Australia and is now widespread across the state. This species is classified as a target biosecurity species by the Department of Fisheries, Government of Western Australia. However, limited information on the biology of this ascidian is available for Australian waters. The aim of this study was to gather baseline information on the temporal variation in growth, survival, and reproduction of D. perlucidum. The mean average colony area was significantly higher in summer (29.7 cm² ) decreasing towards winter (3.3 cm² ). Colonies produced larvae year round with maximum production (1109.0 larvae cm-2 ) and highest recruitment (0.90 settlers cm-2 ) in summer. Larva density was positively correlated to salinity (r = 0.965) and chlorophyll a concentration (r = 0.958) in the water column. From a management point of view, the decrease in colony size, larvae production, and recruitment of D. perlucidum during winter could offer the best opportunity for the control or eradication of this ascidian at specific locations in the state. [ABSTRACT FROM AUTHOR]

Codium fragile subsp. fragile (Suringar) Hariot is a large, dichotomously branched green alga that has invaded many temperate locations around the globe. Despite its wide distribution and pest status, there are few accounts of Codium fragile subsp. fragile that provide morphological descriptions, including illustrations, for comparison. In 2008, a seaweed sample suspected to be Codium fragile subsp. fragile was collected from Albany, Western Australia. As this taxon superficially resembles other local erect and dichotomously branching Codium species, a detailed morphological and molecular analysis of the suspect alga was conducted. Investigations confirmed the identity of this alga as the invasive subspecies Codium fragile subsp. fragile. This represents the first record of this species in Western Australia. [ABSTRACT FROM AUTHOR]

In 2010, Didemnum perlucidum F. Monniot, 1983, a potentially invasive colonial ascidian, was found for the first time in Western Australia (WA). During routine introduced marine pest monitoring along the WA coast in 2011-2012, the Department of Fisheries confirmed additional disjunct populations in a span of ∼2,800 km along the coast. Colonies of the ascidian were apparently flourishing in water temperatures from tropical through to temperate. Colour was not a reliable detection method for this colonial ascidian. Colonies in winter showed the expected senescence, becoming smaller, friable and often partially detached from the substrate. While winter monitoring would reduce likelihood of detection, it may present the best opportunity for eradication. Due to the widespread distribution, eradication of D. perlucidum is now unlikely. However, implementing local control measures to protect high value areas, such as marine parks or protected areas, from incursions remains feasible. A robust monitoring program is vital to detecting D. perlucidum early in its invasion history, and that would provide the best opportunity for local eradication effort. [ABSTRACT FROM AUTHOR]

In April 2011 a single individual of the invasive mussel Perna viridis was detected on a naval vessel while berthed in the temperate waters of Garden Island, Western Australia (WA). Further examination of this and a nearby vessel revealed a small founder population that had recently established inside one of the vessel's sea chests. Growth estimates indicated that average size mussels in the sea chest were between 37.1 and 71 days old. Back calculating an 'establishment date' from these ages placed an average sized animal's origins in the summer months of January 2011 to March 2011. This time period corresponded with an unusual heat pulse that occurred along the WA coastline resulting in coastal waters >3 ºC above normal. This evidence of a spawning event for a tropical species in temperate waters highlights the need to prepare for more incursions of this kind given predictions of climate change. [ABSTRACT FROM AUTHOR]