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Tasman Sea (tasman + sea)
Selected AbstractsPHYLOGEOGRAPHIC STRUCTURE AND CRYPTIC SPECIATION IN THE TRANS-ANTARCTIC MOSS PYRRHOBRYUM MNIOIDESEVOLUTION, Issue 2 2003Stuart F. McDaniel Abstract Many bryophyte species have distributions that span multiple continents. The hypotheses historically advanced to explain such distributions rely on either long-distance spore dispersal or slow rates of morphological evolution following ancient continental vicariance events. We use phylogenetic analyses of DNA sequence variation at three chloroplast loci (atpB-rbcL spacer, rps4 gene, and trnL intron and 3,spacer) to examine these two hypotheses in the trans-Antarctic moss Pyrrhobryum mnioides. We find: (1) reciprocal monophyly of Australasian and South American populations, indicating a lack of intercontinental dispersal; (2) shared haplotypes between Australia and New Zealand, suggesting recent or ongoing migration across the Tasman Sea; and (3) reciprocal monophyly among Patagonian and neotropical populations, suggesting no recent migration along the Andes. These results corroborate experimental work suggesting that spore features may be critical determinants of species range. We use the mid-Miocene development of the Atacama Desert, 14 million years ago, to calibrate a molecular clock for the tree. The age of the trans-Antarctic disjunction is estimated to be 80 million years ago, consistent with Gondwanan vicariance, making it among the most ancient documented cases of cryptic speciation. These data are in accord with niche conservatism, but whether the morphological stasis is a product of stabilizing selection or phylogenetic constraint is unknown. [source] Near real-time spatial management based on habitat predictions for a longline bycatch speciesFISHERIES MANAGEMENT & ECOLOGY, Issue 6 2006A. J. HOBDAY Abstract, Southern bluefin tuna (SBT), Thunnus maccoyii (Castelnau), is a quota-managed species that makes annual winter migrations to the Tasman Sea off south-eastern Australia. During this period it interacts with a year-round tropical tuna longline fishery (Eastern Tuna and Billfish Fishery, ETBF). ETBF managers seek to minimise the bycatch of SBT by commercial ETBF longline fishers with limited or no SBT quota through spatial restrictions. Access to areas where SBT are believed to be present is restricted to fishers holding SBT quota. A temperature-based SBT habitat model was developed to provide managers with an estimate of tuna distribution upon which to base their decisions about placement of management boundaries. Adult SBT temperature preferences were determined using pop-up satellite archival tags. The near real-time predicted location of SBT was determined by matching temperature preferences to satellite sea surface temperature data and vertical temperature data from an oceanographic model. Regular reports detailing the location of temperature-based SBT habitat were produced during the period of the ETBF fishing season when interactions with SBT occur. The SBT habitat model included: (i) predictions based on the current vertical structure of the ocean; (ii) seasonally adjusted temperature preference data for the 60 calendar days centred on the prediction date; and (iii) development of a temperature-based SBT habitat climatology that allowed visualisation of the expected change in the distribution of the SBT habitat zones throughout the season. At the conclusion of the fishing season an automated method for placing management boundaries was compared with the subjective approach used by managers. Applying this automated procedure to the habitat predictions enabled an investigation of the effects of setting management boundaries using old data and updating management boundaries infrequently. Direct comparison with the management boundaries allowed an evaluation of the efficiency and biases produced by this aspect of the fishery management process. Near real-time fishery management continues to be a realistic prospect that new scientific approaches using novel tools can support and advance. [source] Movement and behaviour of large southern bluefin tuna (Thunnus maccoyii) in the Australian region determined using pop-up satellite archival tagsFISHERIES OCEANOGRAPHY, Issue 5 2008TOBY A. PATTERSON Abstract Pop-up satellite archival tags (PSATs) were deployed on 52 large (156,200 cm length to caudal fork) southern bluefin tuna (Thunnus maccoyii) in the western Tasman Sea during the austral winters of 2001,2005. Southern bluefin tuna (SBT) were resident in the Tasman Sea for up to 6 months with movements away from the tagging area occurring at highly variable rates. The data indicated a general tendency for SBT to move south from the tagging area in the Western Tasman Sea. Four individuals migrated west along the southern continental margin of Australia and into the Indian Ocean. Three individuals moved east into the central Tasman Sea, with one individual reaching New Zealand. We also describe the first observed migration of an SBT from the Tasman Sea to the Indian Ocean spawning grounds south of Indonesia. Individuals spent most of their time relatively close to the Australian coast, with an estimated 84% of time spent in the Australian Fishing Zone. SBT favored temperatures between 19 and 21°C, adjusting their depth to the vertical temperature distribution. Distinct diurnal diving patterns were observed and adjustment of depth to maintain constant ambient light levels over a 24-h period. The findings of this study are a significant advance toward greater understanding of the spatial dynamics of large SBT and understanding the connectivity between distant regions of their distribution. [source] Larval fish assemblages along the south-eastern Australian shelf: linking mesoscale non-depth-discriminate structure and water massesFISHERIES OCEANOGRAPHY, Issue 4 2008JOHN P. KEANE Abstract We present findings of the first mesoscale study linking larval fish assemblages and water masses along shelf waters off south-eastern Australia (southern Queensland-New South Wales), based on vertical, non-depth discriminate data from surveys in October 2002 and 2003 (spring) and July 2004 (winter). Clustering and ordination were employed to discriminate between larval assemblages and, for the first time, to define water masses from water column temperature frequencies. Surveys yielded 18 128 larval fishes comprising 143 taxa from 96 identifiable families, with small pelagics accounting for 53% of the total. Three major recurrent larval assemblages were identified during the study, each of which matched one of three water masses, namely East Australian Current to the north (EAC; 20.5,23.4°C), Tasman Sea to the south (TAS; 14.8,17.5°C), and mixed EAC,TAS water in between (MIX; 18.3,19.9°C). All three assemblages were present in spring, whereas only EAC and MIX occurred in the more northerly constrained winter survey. Furthermore, boundaries between the EAC, MIX and TAS assemblages were found to be dynamic, with locations shifting temporally and spatially depending on EAC extent. Assemblage composition differed significantly between water masses across surveys, with EAC,TAS being most dissimilar. Such contrast was due to the presence of tropical/temperate taxa in EAC, primarily temperate-associated taxa in TAS, and a combination of EAC,TAS taxa within MIX consistent with the convergence of both waters. Results highlight the strength of employing larval assemblages as indicators of water masses, particularly in view of the potential effect of climate change on spawning habitats of shelf fishes. [source] Ichthyoplankton-based spawning dynamics of blue mackerel (Scomber australasicus) in south-eastern Australia: links to the East Australian CurrentFISHERIES OCEANOGRAPHY, Issue 4 2008FRANCISCO J. NEIRA Abstract We describe findings of three ichthyoplankton surveys undertaken along south-eastern Australia during spring (October 2002, 2003) and winter (July 2004) to examine spawning habitat and dynamics of blue mackerel (Scomber australasicus). Surveys covered ,860 nautical miles between southern Queensland (Qld; 24.6°S) and southern New South Wales (NSW; 41.7°S), and were mainly centred on the outer shelf including the shelf break. Egg identifications were verified applying mtDNA barcoding techniques. Eggs (n = 2971) and larvae (n = 727; 94% preflexion) occurred both in spring and winter, and were confined to 25.0,34.6°S. Greatest abundances (numbers per 10 m2) of eggs (1214,7390) and larvae (437,1172) occurred within 10 nm shoreward from the break in northern NSW. Quotient analyses on egg abundances revealed that spawning is closely linked to a combination of bathymetric and hydrographic factors, with the outer shelf as preferred spawning area, in waters 100,125 m deep with mean temperatures of 19,20°C. Eggs and larvae in spring occurred in waters of the East Australian Current (EAC; 20.6,22.3°C) and mixed (MIX; 18.5,19.8°C) waters, with none occurring further south in the Tasman Sea (TAS; 16.0,17.0°C). Results indicate that at least some of the south-eastern Australian blue mackerel stock spawns during winter-spring between southern Qld and northern NSW, and that no spawning takes place south of 34.6°S due to low temperatures (<17°C). Spawning is linked to the EAC intrusion, which also facilitates the southward transport of eggs and larvae. Since spring peak egg abundances came from where the EAC deflects offshore, eggs and larvae are possibly being advected eastwards along this deflection front. This proposition is discussed based on recent data on blue mackerel larvae found apparently entrained along the Tasman Front. [source] Three-dimensional seismic structure beneath the Australasian region from refracted wave observationsGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 3 2000Y. Kaiho The earthquakes in the seismicity belt extending through Indonesia, New Guinea, Vanuatu and Fiji to the Tonga,Kermadec subduction zone recorded at the 65 portable broad-band stations deployed during the Skippy experiment from 1993,1996 provide good coverage of the lithosphere and mantle under the Australian continent, Coral Sea and Tasman Sea. The variation in structure in the upper part of the mantle is characterized by deter-mining a suite of 1-D structures from stacked record sections utilizing clear P and S arrivals, prepared for all propagation paths lying within a 10° azimuth band. The azimuth of these bands is rotated by 20° steps with four parallel corridors for each azimuth. This gives 26 separate azimuthal corridors for which 15 independent 1-D seismic velocity structures have been derived, which show significant variation in P and S structure. The set of 1-D structures is combined to produce a 3-D representation by projecting the velocity values along the ray path using a turning point approximation and stacking into 3-D cells (5° by 50 km in depth). Even though this procedure will tend to underestimate wave-speed perturbations, S -velocity deviations from the ak135 reference model exceed 6 per cent in the lithosphere. In the uppermost mantle the results display complex features and very high S -wave speeds beneath the Precambrian shields with a significant low-velocity zone beneath. High velocities are also found towards the base of the transition zone, with highS -wave speeds beneath the continent and high P -wave speeds beneath the ocean. The wave-speed patterns agree well with independent surface wave studies and delay time tomography studies in the zones of common coverage. [source] Southern hemisphere cyclones and anticyclones: recent trends and links with decadal variability in the Pacific OceanINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 11 2007Dr Alexandre Bernardes Pezza Abstract The aim of this paper is to study the association between the extratropical Southern Hemisphere and the decadal variability in the Pacific Ocean (PO). We discuss a pattern of coherent large-scale anomalies and trends in cyclone and anticyclone behaviour in light of the climate variability in the PO over the ERA40 reanalysis period (1957,2002). The two representative PO indices are the Pacific Decadal and Interdecadal Oscillations (PDO and IPO), and here the PDO is chosen owing to it being less associated with the southern oscillation index (SOI). Composites of the indicators of the density and intensity of cyclones/anticyclones given by an automatic tracking scheme were calculated for the years when the PDOI was more than one standard deviation above or below its mean. Although the ERA40 is not free from noise and assimilation changes, the results show a large-scale feature, which seems to be robust and agrees with earlier studies using different data sets. The sea-level pressure shows a strong annular structure related to the PDO, which is not seen for the SOI, with lower pressure around Antarctica during the positive phase and vice versa. More intense (and fewer) cyclones and anticyclones were observed during the positive PDO. This is less consistent for the SOI, particularly during the summer when a different PDO/SOI pattern arises at high latitudes. The trends project a pattern coincident with the positive PDO phase and seem to be linked with the main climate shift in the late seventies. Trends observed over the Tasman Sea are consistent with declining winter rainfall over southeastern Australia. Most patterns are statistically significant and seem robust, but random changes in ENSO may play a part, to a certain degree, in modulating the results, and a physical mechanism of causality has not been demonstrated. Although global warming and related changes in the Southern Annular Mode (SAM) may also help explain the observed behaviour, the large-scale response presented here provides a new insight and would be of considerable interest for further modelling studies. Copyright © 2007 Royal Meteorological Society [source] A mid-shelf, mean wave direction climatology for southeastern Australia, and its relationship to the El Niño,Southern Oscillation since 1878 A.D.INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 13 2005Ian D. Goodwin Abstract Coastal systems behave on timescales from days to centuries. Shelf and coastal wave climatological data from the Tasman Sea are only available for the past few decades. Hence, the records are too short to investigate inter- and multidecadal variability and their impact on coastal systems. A method is presented to hindcast monthly mid-shelf mean wave direction (MWD) for southeastern Australia, based on the monthly, trans-Tasman mean sea-level pressure (MSLP) difference between northern NSW (Yamba) and the north island of New Zealand (Auckland). The MSLP index is calibrated to instrumental (Waverider buoy) MWD data for the Sydney shelf and coast. Positive/negative trans-Tasman MSLP difference is significantly correlated to southerly/easterly Sydney MWD, and to long/short mean wave periods. The 124-year Sydney annual (MWD) time series displays multidecadal variability, and identifies a significant period of more southerly annual MWD during 1884 to 1914 than in the period since 1915. The Sydney MWD is significantly correlated to the Southern Oscillation Index (SOI). The correlation with the SOI is enhanced during periods when the Interdecadal Pacific Oscillation (IPO) is in its negative state and warm SST anomalies occur in the southwest Pacific region. The Sydney MWD was found to be associated with Pacific basin-wide climate fluctuations associated with the El Niño-Southern Oscillation (ENSO). Southerly/easterly Sydney MWD is correlated with low/high MSLP anomalies over New Zealand and the central Pacific Ocean. Southerly/easterly Sydney MWD is also correlated with cool/warm SST anomalies in the southwest Pacific, particularly in the eastern Coral Sea and Tasman Sea. Copyright © 2005 Royal Meteorological Society. [source] Marine biogeographical structure in two highly dispersive gastropods: implications for trans-Tasman dispersalJOURNAL OF BIOGEOGRAPHY, Issue 4 2007Jonathan M. Waters Abstract Aim, Recent genetic and ecological studies of marine invertebrate species with planktotrophic larvae have inferred high rates of gene flow across wide oceanic barriers. We therefore aim to test for the genetic signature of long-distance dispersal in two widespread and abundant marine gastropod taxa. Location, The intertidal and shallow subtidal zones of southern Australia and New Zealand (NZ), which house similar marine invertebrate assemblages despite being separated by the 2000-km-wide Tasman Sea. Methods, We used mtDNA cytochrome oxidase I gene sequence analysis of two gastropod genera exhibiting trans-Tasman distributions, namely Austrolittorina (Littorinidae) (139 specimens; 28 localities) and Scutus (Fissurellidae) (154 specimens; 32 localities). The cool-temperate Australian (A. unifasciata; S. antipodes) and NZ (A. antipodum; S. breviculus) taxa within each genus are morphologically similar but of uncertain taxonomic status. Results, The mtDNA analyses indicate major trans-Tasman genetic discontinuities for both gastropod genera, with no evidence of recent or ongoing intercontinental gene flow. Although both Scutus and Austrolittorina show significant east,west structure within southern Australia , consistent with recent studies of regional marine phylogeography , neither taxon exhibits significant differentiation within NZ. Main conclusions, Morphologically conserved but biogeographically disjunct gastropod populations may exhibit striking phylogeographic discontinuities, even when dispersal abilities appear to be high. On the basis of these data we reject recent calls for the synonymy of NZ and Australian lineages. [source] Border geostrategies: Imagining and administering New Zealand's post-World War One bordersNEW ZEALAND GEOGRAPHER, Issue 3 2008Matthew Henry Abstract:, This paper examines the emergence of an administrative apparatus designed to filter, and in some cases, exclude certain classes of international traveller at the New Zealand border following the end of World War One (WWI). Drawing on Walters' (2004) ideas of ,geostrategies', and specifically focusing on the abolishment of permits for movement across the Tasman Sea, the Undesirable Immigrants Exclusion Act 1919 and the Immigration Restriction Amendment Act 1920, the paper argues that this apparatus was characterized by shifting calculations of risk that shaped international mobility through New Zealand in profoundly uneven ways. [source] | |||||||||||||