Assessment of the barramundi (Lates calcarifer) fishery in the Southern Gulf of Carpentaria, Queensland, Australia.

Wild-capture barramundi (Lates calcarifer) forms the basis of important commercial, recreational and customary Indigenous fisheries in Queensland, with an estimated harvest of about 700 tonnes in 2015 (Saunders et al. 2016). For stock status assessment, barramundi in Queensland are considered to consist of seven genetically distinct populations. Within the Gulf of Carpentaria (GoC), there are two genetic stocks split at around 13⁰ S - a Northern Gulf of Carpentaria stock and a Southern Gulf of Carpentaria stock. The Gulf of Carpentaria Inshore Fin Fish Fishery harvests barramundi from both these stocks, but the current assessment focuses on the Southern Gulf of Carpentaria (Southern GoC) barramundi stock, which produces, on average, greater than 50% of the annual commercial harvest of barramundi in Queensland and was listed as transitional-depleting in the 2016 Status of Australian Fish Stocks report (Saunders et al. 2016)

Adaptive context tree weighting

We describe an adaptive context tree weighting (ACTW) algorithm, as an extension to the standard context tree weighting (CTW) algorithm. Unlike the standard CTW algorithm, which weights all observations equally regardless of the depth, ACTW gives increasing weight to more recent observations, aiming to improve performance in cases where the input sequence is from a non-stationary distribution. Data compression results show ACTW variants improving over CTW on merged files from standard compression benchmark tests while never being significantly worse on any individual file

Assessment of the barramundi fishery in Queensland, 1989-2007

The barramundi (Lates ca/carifer) is an important target species for commercial, recreational and Indigenous fishers across northern Australia. In Queensland, barramundi stocks from the Gulf of Carpentaria (GoC) and the east coast (EC) are managed separately. Updated assessments of both the Goe and EC stocks are reported here. The assessment used catch and effort information from both commercial (CFISH logbooks) and recreational (RFISH surveys) sources. The data were split into six different strata based on the genetic makeup of the stock, leading to six geographical regions with each having its own aggregated total commercial and recreational catch. The analysis proceeded in two stages. The first stage was a standardisation of the catch rate per unit of effort (CPUE) to obtain an estimate of the relative changes in abundance over time. The second stage was fitting a biomass dynamic model to estimate absolute stock biomass and management parameters such as maximum sustainable yield. The primary conclusion drawn from both the standardisation results and the dynamic modelling results is that the data are of insufficient quality to reliably estimate stock biomass or management parameters. This conclusion is based on a number of factors, including (but not limited to): • large fluctuations in the standardised catch rate, which would be biologically implausible if taken as a reliable index of abundance • an inability to find model parameters that lead to a good fit (unless certain parameters are taken past biologically plausible limits) • large uncertainty in parameters estimated from the surplus production model

Total allowable commercial catch review for Queensland spanner crab (Ranina ranina), with data to December 2021

This report was prepared to inform on estimated Total Allowable Commercial Catch (TACC) of spanner crabs and potential economic Gross Value of Production (GVP) in managed area A for the forthcoming two quota years 1 July 2022 to 30 June 2023 and 1 July 2023 to 30 June 2024. The harvest strategy uses standardised commercial (sCPUE) and fishery independent survey (sFIS) catch rates from two years, compared against target rates, to calculate TACC. The average 2020–2021 catch rate indicators from two years, standardised using generalised linear models, were: sCPUE = 0.823 kilograms per dilly-net lift and sFIS = 6.623 crab per ground-line. The stock indexes were the ratio of the indicators compared to their targets. The calculated stock indexes were less than 1, signalling catch rates were below target: sCPUE ratio = 0.6 and sFIS ratio = 0.631. The pooled index was 0.616 (average of the two stock indexes). The pooled index means that the fishery was at 62% of its target. By referencing the pooled index against the harvest strategy, no change in the 847 t TACC was suggested. This TACC corresponded to a potential GVP of around $8 million per year if fully caught

Gearing effects of the patella (knee extensor muscle sesamoid) of the helmeted guineafowl during terrestrial locomotion

Human patellae (kneecaps) are thought to act as gears, altering the mechanical advantage of knee extensor muscles during running. Similar sesamoids have evolved in the knee extensor tendon independently in birds, but it is unknown if these also affect the mechanical advantage of knee extensors. Here, we examine the mechanics of the patellofemoral joint in the helmeted guineafowl Numida meleagris using a method based on muscle and tendon moment arms taken about the patella's rotation centre around the distal femur. Moment arms were estimated from a computer model representing hindlimb anatomy, using hip, knee and patellar kinematics acquired via marker‐based biplanar fluoroscopy from a subject running at 1.6 ms−1 on a treadmill. Our results support the inference that the patella of Numida does alter knee extensor leverage during running, but with a mechanical advantage generally greater than that seen in humans, implying relatively greater extension force but relatively lesser extension velocity

Non-conservation of the valley density and its implications for the observation of the valley Hall effect

We show that the conservation of the valley density in a multi-valley insulator is broken in an unexpected way by an electric field, such as the one that is used to drive the valley Hall effect. This observation explains how a fully gapped insulator (i.e., one without edge states that cross the Fermi level) can support a valley Hall current in the bulk and yet show no valley density accumulation at the edges. If the insulator is not fully gapped, either because there are edge states crossing the Fermi level or because carriers are introduced in the conduction or valence band, then valley density accumulation at the edges is possible, paving the way to a direct observation of the valley Hall effect. However, the magnitude of the accumulation depends crucially on the inclusion of the anomalous electric field term in the continuity equation that relates valley current and density.Comment: 5 pages + 6 pages of supplemental material, 4 figure