3,739 research outputs found
Fisheries biology and management of pink snapper, Pagrus auratus, in the inner gulfs of Shark Bay, Western Australia
No full textThis study explored an important aspect of the basis for the highly complex population structure of pink snapper (Pagrus auratus) within the inner gulfs of Shark Bay, investigated how growth and reproduction differ among these closely-adjacent but separate stocks, and obtained biomass estimates for each stock that are essential for the sustainable management of the regionally-important recreational pink snapper fishery. Using ichthyoplankton data in combination with hydrodynamic modelling, P. auratus eggs and larvae were shown to be retained within localized meso-scale eddies that were coincident with the main inner gulf spawning areas. Such hydrodynamic retention, in conjunction with tagging and otolith chemistry data that indicates very limited movement of juvenile and adult fish, explains how separate pink snapper populations can exist in the adjacent waters of the Eastern Gulf, Denham Sound and Freycinet Estuary. The study found significant variation in maximum age, growth, maturity and spawning time at fine spatial scales. Such variation, unusual for a large, potentially mobile fish inhabiting a marine environment with no obvious physical barriers, is linked to the inner gulfs' marked environmental heterogeneity, the low levels of mixing and historic differences in fishing pressure among the three areas. The daily egg production method (DEPM) was used, for the first time with this species in Western Australia, to provide estimates of spawning biomass of the three separate inner gulf P. auratus stocks. While relatively imprecise, mostly due to imprecision in estimation of daily egg production, these estimates demonstrated that these stocks are very small (measured in tens of tonnes) compared with P. auratus stocks elsewhere in Australia and New Zealand. Biological data and DEPM estimates obtained from this study were incorporated in age-based stock assessment models that have been used to determine the status of inner gulf pink snapper stocks since 2002
Latitudinal and temporal comparisons of the reproductive biology and growth of snapper, Pagrus auratus (Sparidae), in Western Australia
No full textThis study focused on obtaining sound quantitative data on the reproductive biology, length and age compositions and growth of the snapper Pagrus auratus in the waters off Carnarvon at ca 25oS and Perth at ca 32oS on the west coast of Australia and at ca 34oS on the south coast of Western Australia. Sampling thus encompassed both sub-tropical and temperate waters and the geographical range within which this species is abundant in Western Australia. The resultant data were used to explore the ways in which the biological characteristics of P. auratus differ with latitude and thus water temperature. An intensive sampling regime for eggs and spawning individuals of P. auratus was conducted in Cockburn Sound, a large marine embayment in the Perth region at ca 32oS. The resultant data were used to elucidate where and when spawning occurs in this large marine embayment and to determine more precisely the factors that influence the timing of spawning. The implications of the results presented in this thesis for the management of P. auratus, a species that has been subjected to very heavy fishing pressure in recent years, are discussed.
The time and duration of spawning of P. auratus in the subtropical waters of Carnarvon differed markedly from those recorded for this sparid in the temperate and cooler waters of the Perth and the south coast regions. Spawning at Carnarvon occurred predominantly in the five months between late autumn (May) and mid spring (September), whereas it took place mainly in the three months between mid spring (October) and early summer (December) in the Perth region. Spawning of P. auratus on the south coast occurred predominantly in October and November in 2003 and 2004 and scarcely at all in 2005. Gonadal recrudescence was thus initiated when water temperatures were close to their maximum but declining in Carnarvon, and close to their minima and rising in the Perth and south coast regions, respectively. The prevalence of fully mature and spawning females in all three regions was greatest in those months when water temperatures lay between 19 and 21oC. Collation of the data in this thesis and those provided in the literature for other populations showed that the spawning period was related to latitude, occurring far earlier in sub-tropical than temperate waters.
The females and males attained maturity at a far smaller total length (L50) in the Carnarvon region, i.e. 378 and 353 mm, respectively, than in the Perth region, 585 and 566 mm, respectively, and also the south coast region, i.e. 600 and 586 mm. The trends exhibited by the age at maturity parallel those for length, with the A50s for the two sexes increasing from ca 4 years in Carnarvon to ca 5.6 years in the Perth region and nearly 7 years in the south coast region. The L50 and A50 at maturity thus both increased with increasing latitude.
Marginal increment analysis demonstrated that, irrespective of the number of opaque zones in the otoliths of P. auratus, a single such opaque zone is laid down each year in these otoliths. Furthermore, the trends exhibited by the monthly marginal increments showed that the opaque zone is laid down predominantly in winter in the subtropical waters of Carnarvon, as opposed to mainly in spring in the temperate waters of the Perth and south coast regions. Thus, the timing of formation of the opaque zone in the otoliths of P. auratus along the Western Australian coast is not related to the trends exhibited by water temperature, but, in both the Carnvarvon and Perth regions, was coincident with the timing of spawning.
The maximum total lengths recorded for females and males in the Carnarvon region, i.e. 864 and 840 mm, respectively, were considerably less than the corresponding values of 1051 and 1056 mm in the Perth region, and 1083 and 1099 mm in the south coast region. Growth in the Perth and south coast regions was greater than in Carnarvon, as is reflected in, for example, the respective lengths of 820, 720 and 610 mm for females at 10 years of age, as determined from the von Bertalanffy growth equations.
The length and age compositions in the Carnarvon and south coast regions were essentially unimodal, whereas those in the Perth region were bimodal. However, the 'mode' in the length-frequency distribution for the south coast region was located well to the right of that in the Carnarvon region, reflecting relatively lower contributions by individuals of the age cohorts of 3 to 6 years. The marked bimodality in the length-frequency distribution for P. auratus in the Perth region was due to the presence of a group of mainly smaller individuals caught outside Cockburn Sound and another of mainly larger individuals that were caught in Cockburn Sound and which formed part of a spawning aggregation in that embayment.
The proportion of fish > 10 years old in the Carnarvon region declined markedly between 2003 and the following two years, presumably reflecting the effect of heavy fishing pressure. This contributed to the decision by fisheries managers to reduced the TAC in those waters after 2003. Age-frequency data demonstrated that annual recruitment success in Cockburn Sound varied greatly, with the 1991, 1992 and 1996 year classes being particularly strong, and recognizing that the relative numbers of the first two year classes did decline progressively between 2002 and 2004. Annual recruitment was particularly variable in the south coast region, with the catches of the 1996 year class dominating the samples.
The relative number of early stage P. auratus eggs in ichthyoplankton samples collected from Cockburn sound on each of four new moons during the spawning seasons of four consecutive years peaked in November in three of those years, i.e. 2001, 2003 and 2004, and in November/December in the remaining year, i.e. 2002. This showed that spawning in this embayment peaked during these months, at which times the mean sea surface temperatures ranged only from 19 to 20oC.
The prevalence of spawning fraction females in sequential samples demonstrated that spawning peaks at the new and, to a lesser extent, full moons. This helps account for the strong positive correlation between spawning fraction and tidal regime, with spawning being greatest when the tidal range is greatest.
Spawning times, back-calculated from the ages of the eggs collected during ichthyoplankton surveys in Cockburn Sound on each of 16 new moons within the spawning periods of four successive years, demonstrated that, in this embayment, P. auratus spawns at night and within the first three hours of the onset of the ebb tide. The distribution of egg concentrations on the 16 new moons showed that, each year, spawning occurred firstly in the north-eastern area of Cockburn Sound and then in the middle and finally north-western areas of this embayment.
In the Perth region, the marine embayments of Cockburn and Warnbro Sound act as nursery areas for P. auratus during the first two years of life. The majority of 2 to 5 year old fish and a large proportion of the 6 year old fish occupy the marine waters outside the embayments. The remaining 6 year old and almost all of the older fish begin to move in September into particularly Cockburn Sound, where they form relatively large spawning aggregations between October and December, before undergoing a massive emigration from this embayment in December/January. The limited returns from fish that were tagged in Cockburn Sound and were subsequently caught outside this embayment indicate that, following spawning, P. auratus does not tend to move in a particular direction.
Pagrus auratus stocks are heavily exploited in offshore, oceanic waters and in embayments, such as Cockburn Sound, where they are particularly susceptible to capture because of the tendency of this species to form spawning aggregations in these same easily accessible locations each year. The data obtained during this thesis show that the L50 at maturity of females and males in temperate waters, i.e. nearly 600 mm, is far greater than the current minimum legal length (MLL) of 410 mm TL. There is thus a need to increase the MLL and/or reduce fishing pressure on immature individuals in open waters. However, the effectiveness of an increase in the MLL may be limited because there is evidence that P. auratus suffers from fishing-induced barotrauma. Closures of specific areas during the spawning season of P. auratus, such as those that have been applied in Cockburn Sound and Shark Bay, are potentially a very effective method for reducing the effects of heavy fishing on spawning individuals
Fish assemblages associated with natural and anthropogenically-modified habitats in a marine embayment: Comparison of baited videos and opera-house traps
No full textMarine embayments and estuaries play an important role in the ecology and life history of many fish species. Cockburn Sound is one of a relative paucity of marine embayments on the west coast of Australia. Its sheltered waters and close proximity to a capital city have resulted in anthropogenic intrusion and extensive seascape modification. This study aimed to compare the sampling efficiencies of baited videos and fish traps in determining the relative abundance and diversity of temperate demersal fish species associated with naturally occurring (seagrass, limestone outcrops and soft sediment) and modified (rockwall and dredge channel) habitats in Cockburn Sound. Baited videos sampled a greater range of species in higher total and mean abundances than fish traps. This larger amount of data collected by baited videos allowed for greater discrimination of fish assemblages between habitats. The markedly higher diversity and abundances of fish associated with seagrass and limestone outcrops, and the fact that these habitats are very limited within Cockburn Sound, suggests they play an important role in the fish ecology of this embayment. Fish assemblages associated with modified habitats comprised a subset of species in lower abundances when compared to natural habitats with similar physical characteristics. This suggests modified habitats may not have provided the necessary resource requirements (e.g. shelter and/or diet) for some species, resulting in alterations to the natural trophic structure and interspecific interactions. Baited videos provided a more efficient and non-extractive method for comparing fish assemblages and habitat associations of smaller bodied species and juveniles in a turbid environment
Letter From William Bell Scott to My Dear Sir
No full textabstract: Concerning Scott's declining of a book he was to borrow.Curator's Note: Handwritten note on letter reads:
W.B. Seth
Painter & Author
officer of the worldTranscription Details: {Herartto} 13 March
1852.
My dear Sir
I shall not need this copy of the Monograms of Man {I've} mention{ed}, having had 4 sent me by Hill.
Very truly Yours
William B. Scot
Deletion of WASp and N-WASp in B cells cripples the germinal center response and results in production of IgM autoantibodies
No full textHumoral immunodeficiency caused by mutations in the Wiskott-Aldrich syndrome protein (WASp) is associated with failure to respond to common pathogens and high frequency of autoimmunity. Here we addressed the question how deficiency in WASp and the homologous protein N-WASp skews the immune response towards autoreactivity. Mice devoid of WASp or both WASp and N-WASp in B cells formed germinal center to increased load of apoptotic cells as a source of autoantigens. However, the germinal centers showed abolished polarity and B cells retained longer and proliferated less in the germinal centers. While WASp-deficient mice had high titers of autoreactive IgG, B cells devoid of both WASp and N-WASp produced mainly IgM autoantibodies with broad reactivity to autoantigens. Moreover, B cells lacking both WASp and N-WASp induced somatic hypermutation at reduced frequency. Despite this, IgG1-expressing B cells devoid of WASp and N-WASp acquired a specific high affinity mutation, implying an increased BCR signaling threshold for selection in germinal centers. Our data provides evidence for that N-WASp expression alone drives WASp-deficient B cells towards autoimmunity
Belonging and not belonging : understanding India in novels by Paul Scott, Ruth Prawer Jhabvala and V.S. Naipaul.
No full textPhDThis thesis is essentially about the "how" and "why" of the Indian
experience as documented in novels by Paul Scott, Ruth Prawer Jhabvala
and V S Naipaul. The study points to the difficulty of arriving at any
conclusive definition of the country and its people. I show that
differences in attitudes, responses or behaviour are both overt and
subtle, and depend upon whether the writer or the character identifies
with the situation or community with which he or she interacts. It is
the individual's sense of belonging or not belonging to his or her own
group - be this along racial, cultural or gender lines - that accounts
for the differing perspectives evident in these novels. The points-of-
view of the outsider and the insider can therefore be seen as
mutual comments upon the other.
Since the struggle between belonging and not belonging becomes acute
when the old meets the new, focus is centred on communities
experiencing change. These include the British in India, West-Indian
Indians and westernised Indians. Despite their differences, all three
communities share similar reasons for either an acceptance or
rejection of the 'Other'. The thesis argues that the need for
emotional stability compels allegiance to the traditional group, while
the desire for individuality encourages surrender to the new. The
former nurtures a sense of belonging while, it is argued, that the
latter is perceived as the hallmark of those who do not belong.
Tensions arise when both these needs demand to be met. What I show to
be ironic in this struggle between belonging and not belonging is that
those things which individuals overtly reject are often unexpressed
parts of their personal pysche. The barrier between "them" and "us" is
therefore very fragile
Priorities and Principles for Investment in Aquaculture Research by NSW Department of Primary Industries
No full textThis review examined the characteristics of the main aquaculture industries in NSW with respect to current impediments to growth, market development and future opportunities. Within this context, it examined the nature, funding and impacts of the NSW Department of Primary Industries’ current and proposed investments in aquaculture R&D and industry development, as well as its alignment with DPI and industry priorities.aquaculture, research evaluation, public good, Agribusiness, Livestock Production/Industries, Research and Development/Tech Change/Emerging Technologies, Q160,
N-WASP is required for B-cell–mediated autoimmunity in Wiskott-Aldrich syndrome
No full textMutations of the Wiskott-Aldrich syndrome gene (WAS) are responsible for Wiskott-Aldrich syndrome (WAS), a disease characterized by thrombocytopenia, eczema, immunodeficiency, and autoimmunity. Mice with conditional deficiency of Was in B lymphocytes (B/WcKO) have revealed a critical role for WAS protein (WASP) expression in B lymphocytes in the maintenance of immune homeostasis. Neural WASP (N-WASP) is a broadly expressed homolog of WASP, and regulates B-cell signaling by modulating B-cell receptor (BCR) clustering and internalization. We have generated a double conditional mouse lacking both WASP and N-WASP selectively in B lymphocytes (B/DcKO). Compared with B/WcKO mice, B/DcKO mice showed defective B-lymphocyte proliferation and impaired antibody responses to T-cell-dependent antigens, associated with decreased autoantibody production and lack of autoimmune kidney disease. These results demonstrate that N-WASP expression in B lymphocytes is required for the development of autoimmunity of WAS and may represent a novel therapeutic target in WAS
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Impact of the Microbiota on Intestinal Th17 Cells at Steady-State and in Autoimmune Disease
No full textThe gut microbiota is critical in shaping many facets of the host immune system, including the induction of intestinal T helper (Th) 17 cells. Changes in microbiota compositions have been associated with a variety of inflammatory disorders, including type-1 diabetes (T1D) and inflammatory bowel disease (IBD). Th17 responses have also been implicated in these diseases. We therefore sought to elucidate the mechanisms underpinning the links among intestinal symbionts, Th17 cells, and autoimmune disease, by focusing first on the activity of Segmented Filamentous Bacteria (SFB), a murine symbiont that robustly induces intestinal Th17 populations and whose colonization was reported to correlate with protection from T1D in the nonobese diabetic (NOD) mouse. Our studies revealed an unexpected diversity in SFB populations across different animal facilities and illuminated the roles of SAA3, a member of the serum amyloid A family of proteins, and intestinal macrophages in the induction of gut Th17 cells by SFB. We then sought to find human symbionts functionally analogous to SFB in eliciting intestinal Th17 cells, and identified several bacterial species, in particular Bifidobacterium adolescentis, that could, alone, engender Th17 cells in the murine intestine. B. adolescentis and SFB exhibited overlapping but also distinct activities, suggesting multiple routes to gut Th17 induction. Importantly, B. adolescentis exacerbated chemically induced colitis and autoimmune arthritis, and was found to be altered in abundance in the microbiotas of IBD patients, arguing for its pathological relevance. Our results help to inform the search for therapeutic targets in diseases associated with Th17 responses and mucosal dysfunction.Medical SciencesMedical SciencesMicrobiota; Th17; SFB; SAA
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The Role of Innate Immune IL-10 Receptor Signaling in Controlling Intestinal Immune Responses
No full textInterleukin-10 (IL-10) is a key anti-inflammatory cytokine. Patients with deleterious mutations in either IL10 or its receptor (IL10R) develop severe inflammatory bowel disease (IBD) within the first months of life; similarly, Il10rb-/- mice develop spontaneous colitis. The precise mechanisms of IL-10R-dependent control of immune tolerance and intestinal mucosal homeostasis are not well defined. Here I demonstrate that IL-10R signaling in innate immune cells is critical for regulating mucosal homeostasis and prevention of colitis. Loss of IL-10R-dependent signaling caused wild-type CD4+ T cells to become colitogenic in a murine colitis transfer model. Moreover, My data indicate that IL-10R-dependent signals modulated the differentiation and function of bone-marrow-derived macrophages and intestinal macrophages into either pro-inflammatory macrophages or functionally competent anti-inflammatory macrophages in mice. Similarly, monocyte-derived macrophages from very early onset IBD patients harboring loss of function mutations in IL10RA and IL10RB genes also exhibited impaired differentiation and function of pro- and anti-inflammatory macrophages. These results define a unique and non-redundant role for IL-10R signaling in innate immune cell control of intestinal mucosal homeostasis in mice and humans.immune; tolerance; mucosal homeostasis, colitis, IL1
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