Letteratura scientifica selezionata sul tema "Vincent Gulf Region"

Allozyme analysis was used to examine the species-level systematics and stock structure of the Australian blue swimmer crab Portunus pelagicus. Fifty-seven crabs from eight sites were screened in an overview study for allozyme variation at 35 loci. This overview study revealed the presence of two species, differing at a Nei D of 0.14 (2% fixed differences), in the Darwin region of northern Australia. One of these species corresponds to the common P. pelagicus found throughout Australia, whereas the other is most likely either an undescribed ‘cryptic’ species, or the east-Asian species P. trituberculatus. In total, 609 P. pelagicus from 11 sites covering three regions in South Australia and two regions in the Northern Territory were then genotyped at seven polymorphic loci and these data assessed, using goodness- of-fit and F-statistics, for the existence of subpopulations. Four discrete subpopulations could be discerned, namely West Coast, Spencer Gulf, and Gulf St Vincent in South Australia, and Darwin–Gove in the Northern Territory. No evidence of population substructuring among sites within each subpopulation was evident from the allozyme data. The results support the current recognition of the three South Australian regions as separate stocks, and suggest that a taxonomic revision of Indo-Pacific Portunus is warranted.

The semi-enclosed environment of the St Vincent Gulf Bioregion and its fauna are impacted by many human activities. Long-term monitoring of cetaceans is vital. Records of collected specimens (173) and those not examined by the South Australian Museum (98 non-specimens) from 2009–2020 were analyzed. Necropsies were carried out on most carcasses using gross, histopathological, and diagnostic assessment of pathogens, organs, and skin lesions. The relative age and circumstance of death were assigned. Baleen whales (five species) and odontocetes (eight species) were studied. Indo-Pacific bottlenose dolphins (Tursiops aduncus) and common dolphins (Delphinus delphis) were frequently recorded and analyzed in detail. Anthropogenic cases were prevalent (21%). Many dolphins (62%) were immature males. Disease (73%) was the most frequently recorded circumstance of death. The most common pathological change was inflammatory disease, including infectious pneumonia. In Indo-Pacific bottlenose dolphins, infectious disease was more prevalent in the greater St Vincent Gulf Bioregion than in the Adelaide Dolphin Sanctuary. Microbe testing confirmed 32 species of bacteria, 2 fungi, and 1 virus. Nematodes and trematodes were recorded throughout the study, sometimes in association with microbes. Toxoplasma gondii was observed in an Indo-Pacific bottlenose dolphin. Severe traumatic injury was recorded in many dolphins, including anthropogenic cases. A tumor (leiomyoma) was described from a single common dolphin. This study provides an important baseline for the future monitoring of emerging infectious and chronic diseases, and anthropogenic threats in the region.

The seagrass Amphibolis antarctica is an important component of coastal soft-sediment ecosystems across southern Australia. Large-scale losses of A. antarctica at several locations have been linked to anthropogenic nutrient inputs. The present study comprised a field survey to test whether the spatial patterns of plant biomass, canopy structure and epiphyte biomass in A. antarctica could be predicted based on expectations related to nutrient status across two regions within Gulf St Vincent, South Australia. Specific predictions were that: (1) plant biomass, plant density, plant height, leaf cluster frequency and leaf frequency are all lower in the east (higher nutrient) region than in the west region; and (2) epiphyte biomass and epiphyte load are higher in the east than in the west. Regional nutrient status was a poor predictor of most of the parameters measured, with the opposite trends to those predicted often occurring. Plant biomass, canopy structure and epiphyte biomass appear to be a result of several site-specific factors that are not fully understood at this time. The results of the present study have significant implications for making generalised predictions and for monitoring A. antarctica on urbanised coasts, and will also be useful for informing ecological studies on plant–epiphyte and plant–animal interactions in A. antarctica ecosystems.

Abstract The geothermal heat flow measured at the surface of the Earth is originated by different heat sources located at different depths of the planet. The main sources of heat flow in the crust are associated with radioactive decay of Uranium, Thorium and Potassium, in rocks. In some regions, additional heat sources must be considered such as exothermic chemical reactions. The value of the heat flow coming from deep regions, designated by “heat from the mantle”, must be obtained using indirect methods. In this work, the geoid height was used as indicator of alterations “in heat from the mantle” values, considering that the density decrease in regions with geoid height increase is related to high temperature values in the upper part of the mantle. The region on study is located in the Atlantic Ocean, SW of Cape St. Vincent and Cadiz Gulf. Temperature-depth values were obtained in twelve points of the region considering heat flow by conduction in the vertical direction, using published heat flow and thermal conductivity data. Layered models were made using data obtained in published seismic profiles. Moho depth values were used as lower boundary of the crust and mantle heat flow variations were made according geoid height increases. Ocean depth values between 2.5 and 4.3 km were used. A value of 5°C was used for temperature at the upper boundary (ocean bottom) of the models. Temperature calculus stops when a value of 1350 °C was attained. Lithosphere thickness is obtained considering this temperature value as temperature at the bottom of the lithosphere. Heat flow density values from 36 to 65.8 mW m−2 were used in the work with “heat from the mantle” values from 33 to 35 mw m−2. Curie Point Temperature (600°C) depths from 33 to 36 km were obtained. Lithosphere thickness values about 97 km were obtained in all the models.

Snapper is a significant fishery species in Australasia whose movement behaviour remains poorly understood. This was addressed in the present study at the within-region scale using acoustic telemetry in the Gulf St Vincent, South Australia. Over 3 years from May 2011, 54 snapper were monitored throughout ~160km2 using 41 acoustic receivers. The dispersion of >500000 detections varied in space and time, reflecting three types of space use, dependent on different types of movement behaviour. One station, near a large shipwreck, accounted for 67.8% of all detections, particularly during winter, when fish were sedentary and site attached. In spring, the fish dispersed throughout the study area to different habitats and, through summer, occupied different larger restricted areas than used in winter. Snapper were highly mobile and demonstrated systematic behaviour at several temporal scales. They moved linear distances of up to ~100km and could achieve tens of kilometres in a day in episodic movements. Through the year, their activity was distributed across areas of hundreds of square kilometres. The regional spatial management regimen was assessed against this enhanced understanding of movement behaviour. A new marine park sanctuary zone that encompassed the shipwreck was appropriately located, but possible benefits of a nearby spatial spawning closure area appear limited.

Adult King George whiting were sampled at 12 localities representing a range of habitat types across South Australia. Sampling was undertaken between March and May for a minimum of 2 years between 1995 and 1998. Fish were aged by otolith interpretation, and reproductive maturity was determined by gonad analysis using macroscopic and histological techniques. In total, 6961 fish comprising 3678 females and 3283 males were considered from four localities in each of three geographic regions. In both Gulf St Vincent and Spencer Gulf, age structures became more complex from north to south, associated with a shift in size towards larger fish. In the simplest age structures, >90% of fish were from the 3-year age class, whereas the age range of the most complex was 3–17 years, with the 3–5 age classes most numerous. Males were more abundant in smaller size classes and females in the larger. Although some fish from each locality showed some gonad development, only at three localities did spawning occur. At these places, populations had the broadest age and size distributions and were in deep water that experienced medium to high wave energy. Since spawning grounds and nursery areas are up to several hundred kilometres apart, the processes of larval advection and adult movement are implicated as obligate processes of the life history.

The characteristics of movement of the South Australian population of King George whiting (Sillaginodes punctata) were determined through analysis of tag and recapture records collected from three tagging periods: (i) 1968–1969; (ii) 1978–1985; and (iii) 1986–1987. The characteristics were compared between the northern and southern parts of two large fishery regions, and determined for fish tagged at different sizes and ages. Fish tagged in the northern Gulf St Vincent and Spencer Gulf moved southwards up to several hundred kilometres, but those tagged in the southern areas showed no systematic directional displacement. Most fish tagged were subadults or young, immature adults at 2–4 years of age. Small, young fish did not move far until a considerable period after tagging, whereas some fish >300 mm total length (TL) at tagging moved substantial distances within only a few weeks. Fish movement resulted in a significant ontogenetic habitat shift, from relatively protected shallow waters that support extensive meadows of seagrass, to southern, exposed, deeper waters and rocky reef. As a result of this systematic, directional displacement the age structures of the fishery catches also varied systematically throughout the two regions. In the northern areas these were simple and dominated by the 3+ age class, whereas in the south they were complex and consisted of the 2+ to 17+ age classes. Because the latter were the spawning populations, fish movement is an obligate step in the life history that ultimately results in supplementation of numbers on the spawning grounds. The consequences for fishery management are discussed.

Three tasks are usually required to introduce new technologies that reduce by-catches in commercial fisheries: (i) identify and quantify the particular by-catch issue that requires the new devices; (ii) develop and test the devices; and (iii) implement the devices into industry by voluntary acceptance and/or legislation. To solve by-catch problems in prawn-trawl fisheries in three regions of Australia, different approaches have been followed with varying success, and their comparison identifies an ideal framework under which such problems can be resolved.In northern Australia’s prawn-trawl fisheries, the main by-catch issues involved turtles and the discard of a large diversity offish species. To quantify these issues, data were obtained from research vessels, industry logbooks and samples from fishers. Before and during this work, modified gears were developed and tested in a flume tank and in the field using research vessels and, to a lesser extent, commercial vessels. Next, a separate project was established to encourage acceptance of the new technologies by industry and involved workshops, newsletters and a library that lent out various by-catch reducing devices to fishers. Voluntary acceptance of the new gears is currently estimated to be 50‐80% in some ports and 0‐20% in others, and a three-phase plan for their legislation is due to occur between 1999 and 2002.In New South Wales, the main by-catch issue was the large number of undersize fish discarded by prawn trawlers as they caught prawns and other species of retained by-catch. Firstly, observer programmes on commercial vessels were used to identify and quantify size- and species-specific by-catches. Then, modifications to fishing gears that reduced the identified problematic by-catches were developed and tested on chartered commercial fishing vessels. Next, involving fishers in this work (and workshops, posters, videos, etc.) led to the voluntary acceptance of the new modifications by the majority of fishers (estimated to be 100% in some fisheries and 50‐100% in others). Finally, the new devices were made mandatory by legislation in several fisheries, with the others to follow within 12 months.In South Australia’s Gulf St. Vincent, the chief by-catch issue mainly came from the prawn-trawl industry itself and concerned the by-catch of small prawns and fish. The approach used was to begin gear-development research without any formal quantification phase. After preliminary trials by industry, only five days of formal tests of new devices were required to recommend a design that was optimal for industry’s (and management’s) requirements. Within two weeks of the completion of the field trials, 100 of the industry was using this new gear voluntarily and its legislation is planned to occur within the next few years to ensure continued compliance.The simple pattern that emerges from these examples is that the sooner industry is fully involved in all stages of the work (driving the issue, quantifying it, developing devices and implementing them), the sooner and more complete is the voluntary acceptance of by-catch reducing fishing technology, and the more painless is the implementation of the relevant legislation.

The Siriella brevicaudata species group from the West Indo-Pacific, defined and designated by Murano & Fukuoka (2008), previously contained five nominal species. In this study we describe five new species in the brevicaudata group: S. bassi sp. nov. from the Bass Strait, southern Australia, S. occulta sp. nov. from the Arabian Gulf, S. muranoi sp. nov. from the coast of Northern Territory, Australia, S. tabaniocula sp. nov. from Ningaloo Reef of Western Australia and Lodestone Reef off Queensland, and S. talbotae sp. nov. from Lizard Island, Queensland, Australia. Furthermore, Siriella hanseni W.M. Tattersall, 1922 from India and S. vincenti W.M. Tattersall, 1927 from South Australia are redescribed based on re-examination of their type material. A re-examination of specimens subsequently attributed to these two species from other geographical regions showed that these were misidentifications, partly representing three of the new species described herein. Siriella gibbosa (Ledoyer, 1970), which was previously synonymized with S. brevicaudata Paulson, 1875 by Bačescu, is revalidated and included within the brevicaudata group. Siriella lacertilis Talbot, 2009, from Lizard Island, is placed within the brevicaudata group. Diagnostic features for all the members of the group and the group itself are updated. As a result of the present study, the brevicaudata group now comprises 12 valid species.

Includes Publication list by the author as appendix A. "July 2003." Includes bibliographical references (leaves 308-324) A stratigraphically detailed taxonomic study of fossil bryozoans within the Late Eocene sediments of the St Vincent Basin, South Australia. These taxa are compared with existing knowledge of fossil and recent faunas in Australia and other regions to enhance understanding of bryozoan evolution and dispersal. Bryozoan taxa and growth forms are used to interpret the palaeoenvironments of the Eocene Vincent Basin.

Includes Publication list by the author as appendix A.
Includes bibliographical references (leaves 308-324)
xi, 324, [36] leaves, 61 leaves of plates : ill (some col.), maps ; 30 cm.
A stratigraphically detailed taxonomic study of fossil bryozoans within the Late Eocene sediments of the St Vincent Basin, South Australia. These taxa are compared with existing knowledge of fossil and recent faunas in Australia and other regions to enhance understanding of bryozoan evolution and dispersal. Bryozoan taxa and growth forms are used to interpret the palaeoenvironments of the Eocene Vincent Basin.
Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2003?