A Kinematically Complete Measurement of the Proton Structure Function F2 in the Resonance Region and Evaluation of Its Moments

We measured the inclusive electron-proton cross section in the nucleon resonance region (W < 2.5 GeV) at momentum transfers Q**2 below 4.5 (GeV/c)**2 with the CLAS detector. The large acceptance of CLAS allowed for the first time the measurement of the cross section in a large, contiguous two-dimensional range of Q**2 and x, making it possible to perform an integration of the data at fixed Q**2 over the whole significant x-interval. From these data we extracted the structure function F2 and, by including other world data, we studied the Q**2 evolution of its moments, Mn(Q**2), in order to estimate higher twist contributions. The small statistical and systematic uncertainties of the CLAS data allow a precise extraction of the higher twists and demand significant improvements in theoretical predictions for a meaningful comparison with new experimental results.Comment: revtex4 18 pp., 12 figure

Tensor Polarization of the phi meson Photoproduced at High t

As part of a measurement of the cross section of $\phi$ meson photoproduction to high momentum transfer, we measured the polar angular decay distribution of the outgoing $K^+$ in the channel $\phi \to K^+K^-$ in the $\phi$ center-of-mass frame (the helicity frame). We find that s-channel helicity conservation (SCHC) holds in the kinematical range where $t$-channel exchange dominates (up to $-t \sim 2.5$ GeV$^2$ for $E_{\gamma}$=3.6 GeV). Above this momentum, $u$-channel production of a $\phi$ meson dominates and induces a violation of SCHC. The deduced value of the $\phi NN$ coupling constant lies in the upper range of previously reported values.Comment: 6 pages; 5 figure

Exclusive ρ0\rho^0 meson electroproduction from hydrogen at CLAS

The longitudinal and transverse components of the cross section for the $e p\to e^\prime p \rho^0$ reaction were measured in Hall B at Jefferson Laboratory using the CLAS detector. The data were taken with a 4.247 GeV electron beam and were analyzed in a range of $x_B$ from 0.2 to 0.6 and of $Q^2$ from 1.5 to 3.0 GeV$^2$. The data are compared to a Regge model based on effective hadronic degrees of freedom and to a calculation based on Generalized Parton Distributions. It is found that the transverse part of the cross section is well described by the former approach while the longitudinal part can be reproduced by the latter.Comment: 6 pages, 4 figure

Migration patterns of fishes of the Blackwood River and relationships to groundwater intrusion

The Blackwood River catchment is one of two in the Southwest Coast Drainage Division to house all eight freshwater fishes endemic to the region and is therefore of high conservation importance. However, salinisation of the upper catchment has led to substantial range reductions of freshwater species downstream to the largely forested region; where fresh groundwater intrusion by the Yarragadee and Leederville aquifers is greatest. This study represents the only long‐term and comprehensive monitoring of freshwater fish populations in the south‐west of Western Australia, and consisted of 27 monitoring events between October 2005 and September 2009; which provided information on spatial and temporal movement patterns and identified indicator species of adequate groundwater intrusion. The overall key implication of this study is that it demonstrates, for the first time, that groundwater plays an important role in maintaining relictual fish fauna in a major river system of this region. This study identifies two species that are appropriate as indicators of river connectivity and in the setting and monitoring of Ecological Water Requirements (EWRs) for this river in light of groundwater extraction, increasing salinisation and reduced rainfall (and thus surface water run‐off and groundwater recharge) as a consequence of climate change. The study specifically identifies Milyeannup Brook (one of two permanently flowing tributaries due to groundwater intrusion) as being of key conservation importance as it houses the only breeding population of the EPBC listed (Vulnerable) Balston’s Pygmy Perch Nannatherina balstoni, and also housed all the other freshwater fishes of the river which were shown to use the system to varying degrees. Microhabitat utilisation by this species within this system during baseflow conditions demonstrated the importance of pool habitats with the Balston’s Pygmy Perch found to only occupy the downstream <1600m of permanent habitat during March (baseflow). To maintain this baseflow population, it is crucial that this groundwater discharge is maintained in Milyeannup Brook. In the main channel of the Blackwood River, the study found a strong relationship between the upstream movement of Freshwater Cobbler Tandanus bostocki through riffle zones and discharge during the baseflow period, i.e. March in 2006, 2007, 2008 and 2009. The species was found to undergo large localised movements in the main channel of the Blackwood River that were variable both spatially and temporally. Movements during low flow periods (i.e. highest proportional contribution by groundwater to total flow) were best explained and highly correlated with amount of discharge. It is proposed these movements are probably related to feeding rather than spawning activity as large numbers of small, immature individuals (the study found the females of the species matured at ~172 mm Total Length (TL)) were recorded moving through the riffle zones. Furthermore, by examining the reproductive biology of the species, peak spawning was shown to occur from October to December (i.e. outside the baseflow period). Subsequent modelling of upstream movements of Freshwater Cobbler over two riffle zones during the driest month (i.e. March) determined that the level of discharge and subsequent riffle depths that would preclude upstream passage by the species were 381.5 l/sec (0.18 m depth) and 101.9 l/sec (0.05 m depth), for the riffles downstream and upstream of the major groundwater discharge zone, respectively. The significance of riffle access to sustaining the population requires further research, however, it is the largest bodied fish of the river and obviously utilises these riffle habitats in large numbers during baseflow. Therefore, if baseflow discharge maintains adequate depth on these riffle zones such that this species is able to access them, then it could be assumed smaller bodied fishes could also access or negotiate them. It 3 is therefore proposed (along with ensuring the sustainability of the Balston’s Pygmy Perch in Milyeannup Brook) that this species should become an indicator of ecological river connectivity during baseflow and be incorporated in monitoring the adequacy of determined EWRs of the river. Furthermore, in terms of an ecological trigger, the rate of future groundwater extraction from the Leederville and Yarragadee Aquifers should not exceed that which will continue to enable this species to access these riffle zones during the baseflow period or lead to a reduction in the baseflow stream length in Milyeannup Brook. These data represent a comprehensive baseline of fish communities in arguably one of the region’s most important river systems, and highlight the value in long term monitoring of a diverse range of aspects relating to the ecology of these fishes. These findings have considerable implication for setting and monitoring Ecological Water Requirements of this and other rivers in this region; particularly in light of regional groundwater extraction pressures and reduced rainfall due to predicted climate change

Canning River – freshwater fishes and barriers to migrations

No abstract availabl

Interannual variation in fish migration patterns and habitats of the Blackwood River and its tributaries: annual progress report

No abstract availabl

Groundwater contribution to baseflow maintains habitat connectivity for Tandanus bostocki (Teleostei: Plotosidae) in a south-western Australian river

A global biodiversity hotspot, south-western Australia is characterised by a highly endemic freshwater fish fauna that is severely impacted by habitat alterations. As is the case with many rivers in this region, the Blackwood River is secondarily salinised as a consequence of agricultural practices and this has caused population depletions of halo-intolerant fishes. This study is the first to examine the role that groundwater intrusion has in maintaining habitat connectivity for an obligate freshwater fish in a secondarily salinised river. We determined the significance of nonsaline groundwater intrusion in maintaining habitat and migratory routes of the freshwater cobbler, Tandanus bostocki during prolonged annual dry periods; characteristic of Mediterranean climatic zones. Tandanus bostocki undertook large, yet spatially and temporally variable, localised movements through riffles. During baseflow, the period of major groundwater influence, movements were significantly associated with discharge. Analysis of gonadal development suggested that such movements were not strictly related to reproduction and were probably for foraging purposes. The study reveals groundwater is crucial in maintaining migratory routes through riffles and suggests T. bostocki may be reliably used as an indicator of aquatic habitat connectivity in light of groundwater extractions and also continued rainfall reductions in this region due to climate change

Survey of Rainbow Trout in Bancell Brook: following the cessation of a stocking programme

No abstract availabl