Correlations of behavioral deficits with brain pathology assessed through longitudinal MRI and histopathology in the R6/1 mouse model of huntington's disease

Huntington's disease (HD) is caused by the expansion of a CAG repeat in the huntingtin (HTT) gene. The R6 mouse models of HD express a mutant version of exon 1 HTT and typically develop motor and cognitive impairments, a widespread huntingtin (HTT) aggregate pathology and brain atrophy. Unlike the more commonly used R6/2 mouse line, R6/1 mice have fewer CAG repeats and, subsequently, a less rapid pathological decline. Compared to the R6/2 line, fewer descriptions of the progressive pathologies exhibited by R6/1 mice exist. The association between the molecular and cellular neuropathology with brain atrophy, and with the development of behavioral phenotypes remains poorly understood in many models of HD. In attempt to link these factors in the R6/1 mouse line, we have performed detailed assessments of behavior and of regional brain abnormalities determined through longitudinal, in vivo magnetic resonance imaging (MRI), as well as an end-stage, ex vivo MRI study and histological assessment. We found progressive decline in both motor and non-motor related behavioral tasks in R6/1 mice, first evident at 11 weeks of age. Regional brain volumes were generally unaffected at 9 weeks, but by 17 weeks there was significant grey matter atrophy. This age-related brain volume loss was validated using a more precise, semi-automated Tensor Based morphometry assessment. As well as these clear progressive phenotypes, mutant HTT (mHTT) protein, the hallmark of HD molecular pathology, was widely distributed throughout the R6/1 brain and was accompanied by neuronal loss. Despite these seemingly concomitant, robust pathological phenotypes, there appeared to be little correlation between the three main outcome measures: behavioral performance, MRI-detected brain atrophy and histopathology. In conclusion, R6/1 mice exhibit many features of HD, but the underlying mechanisms driving these clear behavioral disturbances and the brain volume loss, still remain unclear. © 2013 Rattray et al

Fishery-specific differences in the size selectivity and catch of diamond- and square-mesh codends in two Australian penaeid seines

The selectivities and catch compositions of conventional 30-mm diamond-mesh codends and a new square-mesh design made from 20-mm mesh hung on the bar for river and lagoon penaeid seines in south-eastern Australia were compared. The square-mesh design significantly improved the selectivities of the river seine for school prawns, 'Metapenaeus macleayi' (Haswell), and the lagoon seine for greasyback prawns, 'Metapenaeus bennettae' (Racek & Dall), by increasing their carapace length at 50% probability of retention (L50) and by decreasing between-haul variability in selectivity. The presence of weed reduced the L50 for greasyback prawns caught in the conventional diamond-mesh codend during the lagoon-seine experiment. The differences among codend performances are discussed in terms of the differing methods of operation and composition of catches between the seines. These differences highlight the need to develop and manage modifications to improve the selectivity of fishing gears on a fishery-specific basis

Improving Selectivity in an Australian Penaeid Stow-net Fishery

Two experiments were conducted in an Australian penaeid stow-net fishery to: (i) validate the use of a fine-meshed cover for determining the selectivity of codends, and (ii) use this cover to quantify and compare the selectivity of a conventional 30-mm diamond-mesh codend and two new square-mesh designs made from 20- and 30-mm mesh, hung on the bar. In the first experiment the codend cover had minimal impact on the fishing performance of the stow net. The 30-mm square-mesh codend tested during the second experiment significantly improved the selectivity of the stow net, measured as an increase in school prawn ('Metapenaeus macleayi' Haswell, 1879) carapace length at 50% probability of retention (L50), and a reduction in the unwanted bycatches of juvenile eastern king prawns ('Penaeus plebejus' Hess, 1865) and small, non-commercial fish. However, a concomitant increase in selection range (SR) indicated that unacceptable quantities of target-sized school prawns escaped. In contrast, the 20-mm square- and 30-mm diamond-mesh codends were virtually non-selective for the sizes of school prawns encountering the gear. Compared to the 30-mm diamond-mesh codend, the 20-mm square-mesh codend did, however, reduce the quantities of eastern king prawns and non-penaeid bycatch retained. The results are attributed to the geometries of the codends tested and provide directions for future research into modifications to improve the selectivity of stow nets

Aspects of the reproductive biology of dusky, spinner and sandbar sharks (Family Carcharhinidae) from the Tasman Sea

Increased harvest pressure exerted on sharks worldwide has created a necessity for more information concerning the basic biology of targeted species. This study marks the first dedicated assessment of the reproductive biology of Carcharhinus obscurus, C. brevipinna and C. plumbeus in eastern Australian waters, where these species support a demersal longline fishery. We found all three to be late maturing species of low reproductive output, suggestive of an overarching susceptibility to stock depletion in the region. Length- (L₅₀, cm LT) and age-at-maturity (A₅₀, years), for females and males were respectively 281.1 and 15.5, and 271.9 and 14.6 for C. obscurus; 224.9 and 10.1, and 208.9 and 8.5 for C. brevipinna; and, 174.8 and 9.5, and 164.5 and 7.0 for C. plumbeus. Uterine fecundity (i.e. litter size) was observed at 5-12 (x = 9.6), 5-14 (x = 10.6) and 3-12 (x = 7.8) for the same three species respectively, and increased significantly with maternal length in C. brevipinna. Length-at-birth (L0, cm LT) ranged from 92 to 96 for C. obscurus, 79-82 for C. brevipinna and 66-76 for C. plumbeus, and all three species exhibited lengthy gestation periods, overall embryonic sex ratios of 1:1 and synchronous parturition in autumn. However, given limitations with respect to sample size and temporal distribution inherent in this study, the reproductive parameters defined herein are necessarily preliminary. Nevertheless, this research challenges a range of findings emanating from other parts of the world and, in doing so, raises pertinent questions relating to the resilience to targeted fishing activities of these species in New South Wales waters compared to other oceanic regions. Moreover, it reinforces the importance of locally derived demographic parameters for population modelling and stock assessment.13 page(s

Modelling between-haul variability in the size selectivity of trawls

The selectivity of fishing gear can vary considerably from set to set even when deployment is replicated under controlled conditions. Analysis of data from size-selectivity experiments will be misleading if this between-deployment variability is not taken into consideration. Here, two approaches are presented for including the effect of between-haul variability when performing size-selectivity experiments for trawls. The first is a simple ad hoc approach that provides a "catch-all" estimate of variability that also takes into account the effect of subsampling the catches. The second is a formal model of random between-haul variability that is fitted via maximum likelihood. The two approaches are applied to both covered-codend and twin-trawl selectivity experiments. The first method is seen to be more intuitive and interpretable, especially when selectivity may depend on catch size, but is limited in its ability to cope with complex experimental designs

The utility of square mesh to reduce bycatch in Hawkesbury River prawn trawls

In New South Wales (NSW), Australia, small

Improving selectivity in an Australian penaeid stow-net fishery

Two experiments were conducted in an Australian penaeid stow-net fishery to: (i) validate the use of a fine-meshed cover for determining the selectivity of codends, and (ii) use this cover to quantify and compare the selectivity of a conventional 30-mm diamond-mesh codend and two new square-mesh designs made from 20- and 30-mm mesh, hung on the bar. In the first experiment the codend cover had minimal impact on the fishing performance of the stow net. The 30-mm square-mesh codend tested during the second experiment significantly improved the selectivity of the stow net, measured as an increase in school prawn (Metapenaeus macleayi Haswell, 1879) carapace length at 50% probability of retention (L), and a reduction in the unwanted bycatches of juvenile eastern king prawns (Penaeus plebejus Hess, 1865) and small, non-commercial fish. However, a concomitant increase in selection range (SR) indicated that unacceptable quantities of target-sized school prawns escaped. In contrast, the 20-mm square- and 30-mm diamond-mesh codends were virtually non-selective for the sizes of school prawns encountering the gear. Compared to the 30-mm diamond-mesh codend, the 20-mm square-mesh codend did, however, reduce the quantities of eastern king prawns and non-penaeid bycatch retained. The results are attributed to the geometries of the codends tested and provide directions for future research into modifications to improve the selectivity of stow nets

The utility of square mesh to reduce bycatch in Hawkesbury River prawn trawls

Will Macbeth and team test square-mesh codends in the Hawkesburry River prawn-trawl fishery

Increasing codend mesh openings: An appropriate strategy for improving the selectivity of penaeid fishing gears in an Australian estuary?

This study investigates the effects of increasing the lateral mesh openings in codends on the size and species selectivity of lagoon and river seines and a stow net used to target penaeid prawns (eastern king ('Penaeus plebejus'), school ('Metapenaeus macleayi') and greasyback prawns ('M. bennettae')) in Wallis Lake, New South Wales, Australia. Compared with conventional codends made from 36-mm diamond-shaped mesh, new designs made from 25- and 29-mm mesh hung on the bar (i.e. square-shaped mesh) significantly reduced the catches of lagoon seine. In contrast, owing to gear-specific operational characteristics such as a slower hauling speed, there were few detectable effects of altering mesh openings in the codend of the river seine. The results are discussed in terms of the differences in the gears used and their particular selection mechanisms. We conclude that, pending further trials, codends made from a mesh size approaching 29mm, hung on the bar, would provide appropriate size- and species-selection for Wallis Lake stow nets and lagoon seines. Further research is required, however, to examine the utility of operational changes to river seines and/or alterations to mesh size and configuration in the wings and body to improve selectivity

Reducing the short-term mortality of juvenile school prawns ('Metapenaeus macleayi') discarded during trawling

A field experiment was carried out in southeastern Australia to assess the short-term mortalityand stress incurred by juvenile school prawns ('Metapenaeus macleayi') discarded froman estuarine trawler. Some 35% of the prawns died up to 72 h after being caught in a trawl,exposed to air during sorting and separation from the retained catch (as per normal commercialprocedures), then discarded into replicate cages. Total mortality was partitioned intothat caused by trawling (about 16% of mortalities), and by subsequent sorting and grading(about 19%). Assuming that the majority of the non-penaeid bycatch is excluded fromtrawls (by the use of bycatch reduction devices), the latter mortalities could be almost eliminatedby sorting and separating unwanted school prawns in water-filled compartments.Emersion stress was measured as concentrations of L-lactate in the haemolymph, whichwere elevated for at least 40 min following capture, but similar among all trawled treatments.L-lactate levels decreased within the first 24 h post-capture, then remained constantover at least the next 48 h, and were greater than baseline levels. The potential benefits associatedwith subtle changes to handling practices onboard estuarine trawlers are discussed