Reference 18667

1. Summary Earlier studies of inshore bioregions identified the need for a large-scale, faunal-based bioregionalisation of offshore demersal habitats in the Australian Exclusive Economic Zone (EEZ). In this project, provincial and biomic regionalisations of the EEZ beyond the coastal zone were produced from validated national datasets for deepwater demersal fishes (defined for this study as fishes found at depths greater than 40 m). In this project, critical information on the geographic and depth distributions of fishes were used to provide the first comprehensive biogeographic appraisal of Australia’s deepwater demersal fish fauna, and the first anywhere at such a large scale. Of the almost 1500 species examined by the project, 21% do not have full scientific names and many of these will be new to science. The distributions of deepwater fishes provide a surrogate of marine faunal distributions across the Australian EEZ. The study discovered evidence of strong patterns in the distribution of Australian deepwater fishes (faunal substructure), with some obvious parallels to the patterns inshore, as well as some marked differences. Eight deepwater provincial units were identified (the Cape, North Eastern, Central Eastern, Tasmanian, Southern, Central Western, North Western and Timor Provinces), as well as indicator species that characterise each province (see map in Figure 10). Notably, the fauna is less complex offshore than inshore in temperate Australia, but more complex on the Australian slope than on the shelf in the tropical Indian and Pacific Oceans. A well-defined Tasmanian province adjoins a more pronounced, cool temperate inshore unit (the Maugean Province). Similarly, the Central Eastern Province off New South Wales coincides with an eastern warm temperate unit inshore, the Peronian Province. The offshore pattern in the Great Australian Bight appears less complex, with evidence for only a single province across this part of southern Australia, whereas there are separate inshore provinces (in south-western Australia and the South Australian gulfs). On the other hand, a strong secondary provincial structure, consisting of a suite of widespread southern Australian species, is evident in deepwater. A subtropical unit off western Australia weakly coincides with an equivalent inshore unit. However, the single tropical provinces inshore, off both the north-west and north-east coasts respectively (the Damperian and Solanderian Provinces), are both represented offshore by two distinct deepwater provinces. In each of the eight deepwater provinces, there are strong patterns of bathymetric zoning of the fauna, which indicate the presence of biomes at different depths. This means that the widespread stratified partitioning of provincial faunas by depth, detected earlier in the South-east Marine Region (SEMR) by CSIRO (2001), is widespread throughout the EEZ. In the present study, three biomes were identified on the continental slope (upper slope, mid-upper slope and mid-slope), as well as an ill-defined unit on the outer continental shelf. Biomic patterns on the continental shelf determined by other studies were unclear, and the data will need to be combined with coastal data in a more comprehensive analysis. A well-developed faunal assemblage, known as the upper slope biome, occurs just below the continental shelf break in each deepwater province (ca 300–520 m). The depth ranges of this biome varied only slightly between provinces; it is slightly shallower in the east than in other areas off the Australian coast. A strong mid-slope band is evident at similar depths (ca 860–1140 m) in all provinces. An additional, less obvious biome was identified on the mid-upper slope between 590–830 m. This biome persisted in all provinces, except the Timor Province. Assemblages beyond the mid-slope could not be clearly evaluated due to a lack of data, but species confined to the deep slope indicate the existence of a lower slope biome, probably beyond 1600 m. Beyond the continental slope (ie, deeper than 2000 m), where the fauna is not well known but thought to become more homogeneous, geological data will be needed as surrogates for the biota. The methods adopted for this project required the development of innovative, world-first solutions to facilitate rapid assessment of the accuracy and quality of literally thousands of literature records and 2 specimens, to allow construction of realistic bioregionalisations. Consultation, both within the project team and externally, was an essential part of refining the scientific approach throughout the project. New tools developed for visualising and analysing data will greatly enhance the national biological baseline and research capability. The mapping tools developed in this project could be customised to produce an interrogative database that would enable the user to produce sub-lists of the fish fauna at any geographic location in the Australian EEZ. For this to happen, the geographic data (converted to 1-dimensional string data) produced from inshore and offshore regionalisations would need to be amalgamated into a uniform data format. If developed, this database would enable managers and researchers to instantaneously determine the fish composition of any marine bioregional unit, from provincial to geomorphological scales, and between any depth intervals. The database could incorporate images and key characteristics of species, thus providing a unique means of characterising and accessing our marine biodiversity. This prototype could be expanded to include invertebrates and marine plants. This project has greatly advanced our knowledge of Australian deepwater fishes, but serious knowledge gaps still exist in our EEZ region, mainly through inadequate research material and a lack of sampling coverage of some regions. Our knowledge of the bioregions will improve dramatically if and when these regions are surveyed. The highest priorities are two relatively accessible, but surprisingly little known regions: the continental shelf off south-west Australia, and the continental slopes off north-east and northwest Australia. Also, our interpretation of the fish data could have been improved if more objective methods of analysing the data were available. New spatial statistic methods may need to be derived, but modified forms of methods used in classical systematics, such as cladistics, could help to interpret the evolutionary history of the bioregions. Biogeographic interpretations have been undertaken for many marine groups of plants and animals in our region, but these patterns have never been assimilated to explain the present provincial or biomic structure of Australia’s marine biota.