Nicholas J. Bax

Marine invasive alien species: a threat to global biodiversity

Invasive alien marine species threaten biodiversity, marine industries (including fishing and tourism) and human health, and unlike oil spills only get worse with time. While some progress is being made internationally on the 10,000 species estimated to be in transit around the world in the ballast water, effective solutions are a long way off; meanwhile the majority of vectors is being ignored. A systematic approach to invasive alien marine species is required to target the means and location of the most effective management actions. Cooperation among regional trading partners will be essential to effectively manage the threat.

Diets and trophic guilds of demersal fishes of the south-eastern Australian shelf

A total of 8200 stomach samples was collected from 102 fish species caught by trawl or gillnet during research surveys on the south-eastern Australian shelf from 1993 to 1996. Diet compositions were analysed based on percentages of wet weight of prey. Of the total fish examined, 70 species had sufficient stomach samples (i.e. >10) for further analysis. Ten trophic guilds were identified from cluster analysis. Benthic prey dominated the diets. However, analysis on a subset of 28 abundant species that were commercially and ecologically important, showed that pelagic prey was dominant, particularly for 12 quota species. This suggests that pelagic production contributes significantly to the trawl fishery production. Further analysis on the diets of these 28 species found that although fish was more important than invertebrate prey, there was no evidence of significant predation on commercially important species (quota species) by other fish species. A food web diagram was constructed, mostly based on the diet compositions, guild structure and relative abundance of commercially and ecologically important fish species, to show major trophic interactions of the shelf ecosystem.

Delineating fish-habitat associations for spatially based management: an example from the south-eastern Australian continental shelf

A multi-scale, multi-gear survey identified the spatial structure and compositions of fish communities from a range of seabed types on the south-eastern Australian continental shelf (25 m to ∼200 m depth). Most communities are species-rich and contain many shared species. Multivariate analysis of distributions of 201 fishes showed communities to be correlated with depth, latitude and seabed type; correlation with hydrodynamic climate is suggested by patterns in morphology. Depth-related patterns occurred on soft-sediment and hard substrata; strong latitudinal (south-west/north-east) patterns identify the area as a faunal transition zone with a major faunal disjunction extending across the shelf. Community patterns were overlaid on distributions of substrata to produce a biophysical map. This mapping process is discussed in the context of spatial management: the ecologically significant scale at which to map habitat features and definition of management units for ecosystem-based management. A hierarchy of scaled ecological units is being developed for Australias National Representative System of Marine Protected Areas (NRSMPA); given the scope of the NRSMPA initiative, surrogate measures of community structure will be required. Maps of substrata and topography, interpreted in the context of the broader depth and latitudinal community structure and as modified by hydrography, may provide one useful surrogate.

Seabed habitat on the south-eastern Australian continental shelf: context, vulnerability and monitoring

A hierarchical approach to mapping seabed habitat is presented. A provincial scale survey that included hydrography and geology provided the context for interpreting habitat use and vulnerability. A megascale map, developed in cooperation with local fishers, identified major seabed features (kilometres to 10s of kilometres). Vulnerability of a feature was defined as its resistance to physical modification and its resilience, or capacity to recover, on removal of the modifier. Vulnerability was assessed from geological, biological and oceanological properties. Inner-shelf sandstone and limestone reefs that were exposed and weathered during the last ice age, and shelf-break bryozoan patch reefs, appear to be the most vulnerable of the hard-grounds to physical disturbance. In contrast, larger, high-relief, outer-shelf fossiliferous limestone reefs appear relatively invulnerable to physical disturbance from fishing. Megascale features were the focus of detailed physical and biological sampling at the mesoscale level (10 m to km), the level of resolution necessary for establishing baseline conditions and monitoring change. The hierarchical approach used here to map seabed habitat amalgamates scientific and fishers’ information. Approached in this way, habitat mapping has the potential to build a common framework of knowledge on which effective spatial management can be based.

Marine biodiversity in the Australian region.

The entire Australian marine jurisdictional area, including offshore and sub-Antarctic islands, is considered in this paper. Most records, however, come from the Exclusive Economic Zone (EEZ) around the continent of Australia itself. The counts of species have been obtained from four primary databases (the Australian Faunal Directory, Codes for Australian Aquatic Biota, Online Zoological Collections of Australian Museums, and the Australian node of the Ocean Biogeographic Information System), but even these are an underestimate of described species. In addition, some partially completed databases for particular taxonomic groups, and specialized databases (for introduced and threatened species) have been used. Experts also provided estimates of the number of known species not yet in the major databases. For only some groups could we obtain an (expert opinion) estimate of undiscovered species. The databases provide patchy information about endemism, levels of threat, and introductions. We conclude that there are about 33,000 marine species (mainly animals) in the major databases, of which 130 are introduced, 58 listed as threatened and an unknown percentage endemic. An estimated 17,000 more named species are either known from the Australian EEZ but not in the present databases, or potentially occur there. It is crudely estimated that there may be as many as 250,000 species (known and yet to be discovered) in the Australian EEZ. For 17 higher taxa, there is sufficient detail for subdivision by Large Marine Domains, for comparison with other National and Regional Implementation Committees of the Census of Marine Life. Taxonomic expertise in Australia is unevenly distributed across taxa, and declining. Comments are given briefly on biodiversity management measures in Australia, including but not limited to marine protected areas.

Development and evaluation of a PCR-based test for detection of Asterias (Echinodermata : Asteroidea) larvae in Australian plankton samples from ballast water

The northern Pacific seastar, Asterias amurensis, spread to Tasmania in the 1980s from its native range in the North Pacific. The seastar has subsequently established in Port Phillip Bay on mainland Australia. Transportation of larvae in ballast water is one vector for these introductions and is likely to contribute to additional range expansion of this species. Larval identification methods are critical to assess risks of further transport to uninvaded ecosystems; however, morphological identification of larval asteroids is impractical and unreliable. Therefore, we have developed a sensitive PCR-based method that specifically detects Asterias DNA. The method works on isolated seastar larva, mixed plankton and ballast water samples. Trials using uninfected ballast water samples spiked with known numbers of A. amurensis larvae indicate that the technique can detect single larva in 200 mg of plankton. The test also detects other Asterias species; therefore, discrimination between seastars within the genus Asterias was accomplished using denaturing gradient gel electrophoresis (DGGE). Currently, this method is being used to facilitate research on ballast water transport, distribution and the ecology of A. amurensis larvae. The general approach can be expanded to provide a rapid and cost-effective approach for detecting a suite of marine species in ballast water and environmental samples.

Genetic control of invasive fish: technological options and its role in integrated pest management

Genetic options for the control of invasive fishes were recently reviewed and synthesized at a 2010 international symposium, held in Minneapolis/St. Paul, MN, USA. The only option currently available “off-the-shelf” is triploidy, which can be used to produce sterile males for a release program analogous to those widely and successfully used for biological control of insect pests. However, the Trojan Y and several recombinant options that heritably distort pest population sex ratios are technologically feasible, are at or are close to proof-of-concept stage and are potentially much more effective than sterile male release programs. All genetic options at this stage require prolonged stocking programs to be effective, though gene drive systems are a potential for recombinant approaches. They are also likely to differ in their current degree of social acceptability, with chromosomal approaches (triploidy and Trojan Y) likely to be the most readily acceptable to the public and least likely to require changes in legislative or policy settings to be implemented. Modelling also suggests that the efficacy of any of these genetic techniques is enhanced by, and in turn non-additively enhance, conventional methods of pest fish control.

A Southern Hemisphere Bathyal Fauna Is Distributed in Latitudinal Bands

The large-scale spatial distribution of seafloor fauna is still poorly understood. In particular, the bathyal zone has been identified as the key depth stratum requiring further macroecological research, particularly in the Southern Hemisphere. Here we analyze a large biological data set derived from 295 research expeditions, across an equator-to-pole sector of the Indian, Pacific, and Southern oceans, to show that the bathyal ophiuroid fauna is distributed in three broad latitudinal bands and not primarily differentiated by oceanic basins as previously assumed. Adjacent faunas form transitional ecoclines rather than biogeographical breaks. This pattern is similar to that in shallow water despite the order-of-magnitude reduction in the variability of environmental parameters at bathyal depths. A reliable biogeography is fundamental to establishing a representative network of marine reserves across the worlds oceans.

Development and evaluation of a PCR based assay for detection of the toxic dinoflagellate, Gymnodinium catenatum (Graham) in ballast water and environmental samples

Gymnodinium catenatum is a bloom forming dinoflagellate that has been known to cause paralytic shellfish poisoning (PSP) in humans. It is being reported with increased frequency around the world, with ballast water transport implicated as a primary vector that may have contributed to its global spread. Major limitations to monitoring and management of its spread are the inability for early, rapid, and accurate detection of G. catenatum in plankton samples. This study explored the feasibility of developing a PCR-based method for specific detection of G. catenatumin cultures and heterogeneous ballast water and environmental samples. Sequence comparison of the large sub unit (LSU) ribosomal DNA locus of several strains and species of dinoflagellates allowed the design of G. catenatum specific PCR primers that are flanked by conserved regions. Assay specificity was validated through screening a range of dinoflagellate cultures, including the morphologically similar and taxonomically closely related species G. nolleri. Amplification of the diagnostic PCR product from all the strains of G. catenatum but not from other species of dinoflagellates tested imply the species specificity of the assay. Sensitivity of the assay to detect cysts in ballast water samples was established by simulated spiked experiments. The assay could detect G. catenatum in all ‘blank’ plankton samples that were spiked with five or more cysts. The assay was used to test environmental samples collected from the Derwent river estuary, Tasmania. Based on the results we conclude that the assay may be utilized in large scale screening of environmental and ballast water samples.

Ecological, behavioral, and genetic factors influencing the recombinant control of invasive pests

Invasive species are a major threat to biodiversity, cost the world economy billions of dollars annually, and are often difficult, if not impossible, to control using current approaches. Recombinant technologies could revolutionize management of such pests but would be subject to a range of genetic, behavioral, and ecological factors that could limit their efficacy or applicability. We use a realistically parameterized combined population dynamics/genetics model to assess the potential of, and constraints on, a suite of recombinant approaches that have been suggested for pest control. We show that, of the options suggested to date, a genetic construct that distorts operational sex ratios by sterilizing, killing, or sex-changing one gender and being inherited through the other, is not only potentially the most effective means of pest control, but also one that remains effective over the widest range of ecological and behavioral conditions. All methods, however, are sensitive in particular to the degree of density dependence in the pest population and to operational issues such as maximum copy number and stocking levels, which affect introgression rates. Optimal investment strategies for an integrated pest management program that includes the nonlinear interactions of recombinant strategies and complementary management options can be assessed through the sensitivity analyses. The subtle effects of even minor variability in some parameters, such as extra mortality due to the presence of the construct, further suggest that genetic techniques be applied in an active adaptive management framework, so that strategies can be regularly optimized as the impacts of a release program are assessed.