ALBERT

Description: We present CO observations towards a sample of six H i-rich Ultradiffuse galaxies (UDGs) as well as one UDG (VLSB-A) in the Virgo Cluster with the Institut de RadioAstronomie Millimétrique (IRAM) 30-m telescope. CO J = 1–0 is marginally detected at 4σ level in AGC 122966, as the first detection of CO emission in UDGs. We estimate upper limits of molecular mass in other galaxies from the non-detection of CO lines. These upper limits and the marginal CO detection in AGC 122966 indicate low mass ratios between molecular and atomic gas masses. With the star formation efficiency derived from the molecular gas, we suggest that the inefficiency of star formation in such H i-rich UDGs is likely caused by the low efficiency in converting molecules from atomic gas, instead of low efficiency in forming stars from molecular gas.

Description: Transformation of refractory cratonic mantle into more fertile lithologies is the key to the fate of cratonic lithosphere. This process has been extensively studied in the eastern North China Craton (NCC) while that of its western part is still poorly constrained. A comprehensive study of newly-found pyroxenite xenoliths from the Langshan area, in the northwestern part of this craton is integrated with a regional synthesis of pyroxenite and peridotite xenoliths to constrain the petrogenesis of the pyroxenites and provide an overview of the processes involved in the modification of the deep lithosphere. The Langshan pyroxenites are of two types, high-Mg# [Mg2+/(Mg2++Fe2+)*100 = ∼ 90, atomic ratios] olivine-bearing websterites with high equilibration temperatures (880 ∼ 970 oC), and low-Mg# (70 ∼ 80) plagioclase-bearing websterites with low equilibration temperatures (550 ∼ 835 oC). The high-Mg# pyroxenites show trade-off abundances of olivine and orthopyroxene, highly depleted bulk Sr-Nd (ƐNd = +11.41, 87Sr/86Sr = ∼0.7034) and low clinopyroxene Sr isotopic ratios (mean 87Sr/86Sr = ∼0.703). They are considered to reflect the reaction of mantle peridotites with silica-rich silicate melts derived from the convective mantle. Their depletion in fusible components (e.g., FeO, TiO2 and Na2O) and progressive exhaustion of incompatible elements suggest melt extraction after their formation. The low-Mg# pyroxenites display layered structures, convex-upward rare earth element patterns, moderately enriched bulk Sr-Nd isotopic ratios (ƐNd = -14.20 ∼ -16.74, 87Sr/86Sr = 0.7070 ∼ 0.7078) and variable clinopyroxene Sr-isotope ratios (87Sr/86Sr = 0.706-0.711). They are interpreted to be crustal cumulates from hypersthene-normative melts generated by interaction between the asthenosphere and heterogeneous lithospheric mantle. Combined with studies on regional peridotite xenoliths, it is shown that the thinning and refertilization of the lithospheric mantle was accompanied by crustal rejuvenation and that such processes occurred ubiquitously in the northwestern part of the NCC. A geodynamic model is proposed for the evolution of the deep lithosphere, which includes long-term mass transfer through a mantle wedge into the deep crust from the Paleozoic to the Cenozoic, triggered by subduction of the Paleo-Asian ocean and the Late Mesozoic lithospheric extension of eastern Asia.

Description: Fishermen are known to try to avoid fishing in stormy weather, as storms pose a physical threat to fishers, their vessels, and their gear. In this article, a dataset and methods are developed to investigate the degree to which fishers avoid storms, estimate storm aversion parameters, and explore how this response varies across vessel characteristics and across regions of the United States. The data consist of vessel-level trip-taking decisions from six federal fisheries across the United States combined with marine storm warning data from the National Weather Service. The estimates of storm aversion can be used to parameterize predictive models. Fishers’ aversion to storms decreases with increasing vessel size and increases with the severity of the storm warning. This information contributes to our understanding of the risk-to-revenue trade-off that fishers evaluate every time they consider going to sea, and of the propensity of fishers to take adaptive actions to avoid facing additional physical risk.

Description: Sardine Sardinops sagax is an ecologically and economically important Clupeid found off the entire South African coast that includes both coastal upwelling and western boundary current systems. Although the management of the sardine fisheries historically assumed a single, panmictic population, the existence of three, semi-discrete subpopulations has recently been hypothesized. We conducted otolith δ18O and microstructure analyses to investigate nursery habitat temperatures and early life growth rates, respectively, of sardine collected from three biogeographic regions around South Africa’s coast to test that hypothesis. Analyses indicated that for both summer- and winter-captured adults and summer-captured juveniles, fishes from the west coast grew significantly slower in water that was several degrees cooler than those from the south and east coasts. This suggests that mixing of sardines between regions, particularly the west and other coasts, is relatively limited and supports the hypothesis of semi-discrete subpopulations. However, the west-south differences disappeared in the results for winter-captured juveniles, suggesting that differences in early life conditions between regions may change seasonally, and/or that all or most winter-captured juveniles originated from the west coast. Further elucidating the interactions between South African sardine subpopulations and the mechanisms thereof is important for sustainable harvesting of this species.

Description: The orogenic development after the continental collision between Laurussia and Gondwana, led to two contrasting associations of mantle-derived magmatic rocks on the territory of the Bohemian Massif: (i) a 340–310 Ma lamprophyre-lamproite orogenic association and (ii) a 300–275 Ma lamprophyre association of anorogenic affinity. Major types of potassic mantle-derived magmatic rocks recognised in the orogenic and anorogenic associations include: (i) calc-alkaline to alkaline lamprophyres, (ii) alkaline “orthopyroxene minettes” (and geochemically related rocks), and (iii) peralkaline lamproites. These three types significantly differ with respect to mineral, whole-rock and Sr–Nd–Pb–Li isotope composition, and spatial distribution. The calc-alkaline lamprophyres occur throughout the entire Saxo-Thuringian and Moldanubian zones, whereas the different types of malte-derived potassic rocks are spatially restricted to particular zones. Rocks of the Carboniferous lamprophyre-lamproite orogenic association are characterised by variable negative εNd(i) and variably radiogenic Sr(i), whereas the rocks of the Permian lamprophyre association of anorogenic affinity are characterised by positive εNd(i) and relatively young depleted-mantle Nd-model ages reflecting increasing input from upwelling asthenospheric mantle. The small variation in the Pb isotopic composition of post-collisional potassic mantle-derived magmatic rocks (of both the orogenic and anorogenic series) implies that the Pb budget of the mantle beneath the Bohemian Massif is dominated by the same crust-derived material, which itself may include material derived from several sources. The source rocks of “orthopyroxene minettes” are characterised by isotopically light (“eclogitic”) Li and strongly radiogenic (crustal) Sr and may have been metasomatised by high-pressure fluids along the edge of a subduction zone. In contrast, the strongly Al2O3 and CaO depleted mantle source of the lamproites is characterised by isotopically heavy Li and high SiO2 and extreme K2O contents. This mantle source may have been metasomatised predominantly by melts. The mantle source of the lamprophyres may have undergone metasomatism by both fluids and melts.

Description: We find that the minor axes of the ultra-diffuse galaxies (UDGs) in Abell 2634 tend to be aligned with the major axis of the central dominant galaxy, at a $gtrsim 95{{ m per cent}}$ confidence level. This alignment is produced by the bright UDGs with the absolute magnitudes Mr 〈 −15.3 mag, and outer-region UDGs with R 〉 0.5R200. The alignment signal implies that these bright, outer-region UDGs are very likely to acquire their angular momenta from the vortices around the large-scale filament before they were accreted into A2634, and form their extended stellar bodies outside of the cluster; in this scenario, the orientations of their primordial angular momenta, which are roughly shown by their minor axes on the images, should tend to be parallel to the elongation of the large-scale filament. When these UDGs fell into the unrelaxed cluster A2634 along the filament, they could still preserve their primordial alignment signal before violent relaxation and encounters. These bright, outer-region UDGs in A2634 are very unlikely to be the descendants of the high-surface-brightness dwarf progenitors under tidal interactions with the central dominant galaxy in the cluster environment. Our results indicate that the primordial alignment could be a useful probe of the origin of UDGs in large-scale structures.

Description: We present a detailed analysis of the gaseous component of the Si K edge using high-resolution Chandra spectra of low-mass X-ray binaries. We fit the spectra with a modified version of the ISMabs model, including new photoabsorption cross-sections computed for all Si ionic species. We estimate column densities for Si i, Si ii, Si iii, Si xii, and Si xiii, which trace the warm, intermediate temperature, and hot phases of the Galactic interstellar medium. We find that the ionic fractions of the first two phases are similar. This may be due to the physical state of the plasma determined by the temperature or due to the presence of absorber material in the close vicinity of the sources. Our findings highlight the need for accurate modelling of the gaseous component before attempting to address the solid component.

Description: The Lu–Hf isotope system and Sr–Nd–Hf–Os isotope systematics of mantle rocks are capable of unravelling the early processes in collision belts, especially in a hot subduction context where the Sm–Nd and U–Pb systems in crustal rocks are prone to resetting owing to high temperatures and interaction with melts during exhumation. To improve models of the Devonian–Carboniferous evolution of the Bohemian Massif, we investigated in detail mafic and ultramafic rocks (eclogite, pyroxenite, and peridotite) from the ultrahigh-pressure and ultrahigh-temperature Kutná Hora Crystalline Complex (KHCC: Úhrov, Bečváry, Doubrava, and Spačice localities). Petrography, multiphase solid inclusions, major and trace element compositions of rocks and minerals, and radiogenic isotopic data document contrasting sources and protoliths as well as effects of subduction-related processes for these rocks. The Úhrov peridotite has a depleted composition corresponding to the suboceanic asthenospheric mantle, whereas Bečváry and Doubrava peridotites represent lithospheric mantle that underwent melt refertilization by basaltic and SiO2-undersaturated melts, respectively. Multiphase solid inclusions enclosed in garnet from Úhrov and Bečváry peridotites represent trapped H2O ± CO2-bearing metasomatizing agents and Fe–Ti-rich melts. The KHCC eclogites either formed by high-pressure crystal accumulation from mantle-derived basaltic melts (Úhrov) or represent a fragment of mid-ocean ridge basalt-like gabbroic cumulate (Spačice) and crustal-derived material (Doubrava) both metamorphosed at high P–T conditions. The Lu–Hf age of 395 ± 23 Ma obtained for the Úhrov peridotite reflects garnet growth related to burial of the asthenospheric mantle during subduction of the oceanic slab. By contrast, Spačice and Doubrava eclogites yield younger Lu–Hf ages of ∼350 and 330 Ma, respectively, representing mixed ages as demonstrated by the strong granulite-facies overprint and trace element zoning in garnet grains. We propose a refined model for the Early Variscan evolution of the Bohemian Massif starting with the subduction of the oceanic crust (Saxothuringian ocean) and associated oceanic asthenospheric mantle (Úhrov) beneath the Teplá–Barrandian at ≥380 Ma, which was responsible for melt refertilization of the associated mantle wedge (Bečváry, Doubrava). This was followed by continental subduction (∼370–360 Ma?) accompanied by the oceanic slab break-off and incorporation of the upwelling asthenospheric mantle into the Moldanubian lithospheric mantle and subsequent coeval exhumation of mantle and crustal rocks at ∼350–330 Ma.

Description: Progress towards ecosystem-based fisheries management calls for useful tools to prioritize actions. To select suitable methods for local circumstances, evaluating approaches used in other jurisdictions can be a cost-effective first step. We tested Productivity Susceptibility Analysis (PSA) to assess the potential vulnerability of the marine fish community in the Skagerrak–Kattegat (Eastern North Sea) to possible interactions with all Swedish fisheries operating in the area. This analysis combines attributes for a species productivity with attributes related to the susceptibility to capture to quantify a single score for vulnerability: high, medium, or low risk. Results indicate that demersal trawl and gillnet fisheries were associated with the highest risk levels if interaction occurs, i.e. having the highest prevalence of species with potentially high vulnerability to the fisheries. Mixed results were seen when comparing the assessment results with available data. The main benefit of utilizing PSA in the area is the comprehensiveness of the assessment, including data-deficient fisheries and species. Drawbacks include potential overestimation of actual risks. Overall, together with available data, PSA in the studied area provides a comprehensive map of potential risks for further actions and may progress a science-based, precautionary management of the area.

Description: While fisheries provide food and employment for hundreds of millions of people, they also can have significant impact on biodiversity. We explore the potential of area-based fisheries management to simultaneously maintain biodiversity and high levels of sustainable food production. We used two illustrative examples of fisheries that have different gear types, areas, and species to evaluate the trade-off between biodiversity and harvest. We calculate the optimal effort by gear and area that maximizes a weighted objective function of biodiversity and harvest, ranging from 100% of the weight on harvest to 100% on biodiversity. We found for both case studies that the trade-off was highly convex, with win–win solutions allowing for high levels of both fishery harvest and conservation. This is achieved by reducing or eliminating fishing effort that negatively impacts high conservation value species while maintaining fishing effort with gears and in areas where there is low conservation impact. We suggest that, in most fisheries, such situations can be found and that effective area-based management can provide for high levels of biodiversity protection and food production.

Description: The Changning–Menglian orogenic belt (CMOB) in the southeastern Tibetan Plateau is an important link between the Longmu Co–Shuanghu suture (LCSS) in the northern Tibetan Plateau and the Chiang Mai–Inthanon and Bentong–Raub sutures in Thailand and Peninsular Malaysia. These belts and sutures are generally regarded as containing the remnants of the oceanic crust of the Palaeo-Tethys that formed by seafloor spreading as a result of the separation of Gondwana- and Eurasia-derived blocks during the Middle Cambrian. In this paper we report the first discovery of abundant unaltered and retrograde eclogites that occur as irregular lenses and blocks in metasedimentary rocks of the CMOB, and these eclogites form an elongate and almost north–south-trending high-pressure (HP)–ultrahigh-pressure (UHP) metamorphic belt that is ∼200 km long and ∼50 km wide. The newly discovered phengite/talc/epidote–glaucophane eclogites, lawsonite–talc–phengite eclogites, dolomite/magnesite–kyanite eclogites and phengite–kyanite-bearing retrograde eclogites have enriched (E-) and normal mid-ocean ridge basalt (N-MORB)-like affinities and mainly positive as well as some negative whole-rock εNd values (–4·34 to +7·89), which suggest an enriched and depleted oceanic lithosphere source for their protoliths. Magmatic zircons separated from the epidote–glaucophane, magnesite–kyanite and (phengite–kyanite-bearing) retrograde eclogites gave protolith ages of 317–250 Ma, which fit well within the time frame of the opening of the Palaeo-Tethys during the Middle Cambrian and its closure during the Triassic. Abundant metamorphic zircons in the eclogites indicate a Triassic metamorphic event related to the subduction of the Palaeo-Tethys oceanic crust from 235 to 227 Ma. Taking into account previous isotopic age data, we now establish the periods of Early–Middle Triassic (246–227 Ma) and Late Triassic (222–209 Ma) as the ages of subduction and exhumation of the Palaeo-Tethyan oceanic crust, respectively. Thermodynamic modelling revealed that the eclogites record distinct HP–UHP peak metamorphic conditions of 23·0–25·5 kbar and 582–610 °C for the phengite–glaucophane eclogites, 24·0–25·5 kbar and 570–586 °C for the talc–glaucophane eclogites, 29·0–31·0 kbar and 675–712 °C for the dolomite–kyanite eclogites, and 30·0–32·0 kbar and 717–754 °C for the magnesite–kyanite eclogites. These P–T estimates and geochronological data indicate that the Palaeo-Tethys oceanic slab was subducted to different mantle depths from 75 km down to 95 km, forming distinct types of eclogite with a variety of peak eclogite-facies mineral assemblages. The eclogites consistently record clockwise metamorphic P–T–t paths characterized by a heating–compression prograde loop under a low geothermal gradient of 5–10 °C km–1, indicating the rapid subduction of cold oceanic crust at a rate of 4·5–6·0 km Ma–1, followed by isothermal or cooling–decompressive retrogression and exhumation at an average rate of 3·2–4·2 km Ma–1. The newly discovered eclogites of the CMOB with their signatures of ocean-crust subduction are petrologically, geochemically and geochronologically comparable with those of the LCSS, providing powerful support for the idea that a nearly 2000 km long HP–UHP eclogite belt extends from the northern Tibetan Plateau to the southeastern Tibetan Plateau, and that it represents the main boundary suture of the Palaeo-Tethyan domain. These results have far-reaching implications for the tectonic framework and complex metamorphic evolution of the Palaeo-Tethyan domain.

Description: Using state-of-the-art high-resolution fully GPU N-body simulations, we demonstrate for the first time that the infall of a dark matter-rich satellite naturally explains a present black hole offset by subparsecs in M31. Observational data of the tidal features provide stringent constraints on the initial conditions of our simulations. The heating of the central region of M31 by the satellite via dynamical friction entails a significant black hole offset after the first pericentric passage. After having reached its maximum offset, the massive black hole sinks towards the M31 centre due to dynamical friction and it is determined to be offset by subparsecs as derived by observations.

Description: In two recent papers published in MNRAS, Namouni and Morais claimed evidence for the interstellar origin of some small Solar system bodies, including: (i) objects in retrograde co-orbital motion with the giant planets and (ii) the highly inclined Centaurs. Here, we discuss the flaws of those papers that invalidate the authors’ conclusions. Numerical simulations backwards in time are not representative of the past evolution of real bodies. Instead, these simulations are only useful as a means to quantify the short dynamical lifetime of the considered bodies and the fast decay of their population. In light of this fast decay, if the observed bodies were the survivors of populations of objects captured from interstellar space in the early Solar system, these populations should have been implausibly large (e.g. about 10 times the current main asteroid belt population for the retrograde co-orbital of Jupiter). More likely, the observed objects are just transient members of a population that is maintained in quasi-steady state by a continuous flux of objects from some parent reservoir in the distant Solar system. We identify in the Halley-type comets and the Oort cloud the most likely sources of retrograde co-orbitals and highly inclined Centaurs.

Description: Strong gravitational lensing has been a powerful probe of cosmological models and gravity. To date, constraints in either domain have been obtained separately. We propose a new methodology through which the cosmological model, specifically the Hubble constant, and post-Newtonian parameter can be simultaneously constrained. Using the time-delay cosmography from strong lensing combined with the stellar kinematics of the deflector lens, we demonstrate that the Hubble constant and post-Newtonian parameter are incorporated in two distance ratios that reflect the lensing mass and dynamical mass, respectively. Through the re-analysis of the four publicly released lenses distance posteriors from the H0LiCOW (H0 Lenses in COSMOGRAIL’s Wellspring) collaboration, the simultaneous constraints of Hubble constant and post-Newtonian parameter are obtained. Our results suggest no deviation from the general relativity; $gamma _{t {PPN}}=0.87^{+0.19}_{-0.17}$ with a Hubble constant that favours the local Universe value, $H_0=73.65^{+1.95}_{-2.26}$ km s−1 Mpc−1. Finally, we forecast the robustness of gravity tests by using the time-delay strong lensing for constraints we expect in the next few years. We find that the joint constraint from 40 lenses is able to reach the order of $7.7{{ m per cent}}$ for the post-Newtonian parameter and $1.4{{ m per cent}}$ for the Hubble constant.

Description: One of the proposed channels of binary black hole mergers involves dynamical interactions of three black holes. In such scenarios, it is possible that all three black holes merge in a so-called hierarchical merger chain, where two of the black holes merge first and then their remnant subsequently merges with the remaining single black hole. Depending on the dynamical environment, it is possible that both mergers will appear within the observable time window. Here, we perform a search for such merger pairs in the public available LIGO and Virgo data from the O1/O2 runs. Using a frequentist p-value assignment statistics, we do not find any significant merger pair candidates, the most significant being GW170809-GW151012 pair. Assuming no observed candidates in O3/O4, we derive upper limits on merger pairs to be ∼11–110 yr−1 Gpc−3, corresponding to a rate that relative to the total merger rate is ∼0.1−1.0. From this, we argue that both a detection and a non-detection within the next few years can be used to put useful constraints on some dynamical progenitor models.

Description: We present extremely deep upper limits on the radio emission from 4U 1957+11, an X-ray binary that is generally believed to be a persistently accreting black hole that is almost always in the soft state. We discuss a more comprehensive search for Type I bursts than in past work, revealing a stringent upper limit on the burst rate, bolstering the case for a black hole accretor. The lack of detection of this source at the 1.07 μJy/beam noise level indicates jet suppression that is stronger than expected even in the most extreme thin disc models for radio jet production – the radio power here is 1500–3700 times lower than the extrapolation of the hard state radio/X-ray correlation, with the uncertainties depending primarily on the poorly constrained source distance. We also discuss the location and velocity of the source and show that it must have either formed in the halo or with a strong asymmetric natal kick.

Description: Swift J004427.3−734801 is an X-ray source in the Small Magellanic Cloud (SMC) that was first discovered as part of the Swift S-CUBED programme in 2020 January. It was not detected in any of the previous 3 yr worth of observations. The accurate positional determination from the X-ray data has permitted an optical counterpart to be identified that has the characteristics of an O9V−B2III star. Evidence for the presence of an infrared excess and significant I-band variability strongly suggests that this is an OBe-type star. Over 17 yr worth of optical monitoring by the OGLE (Optical Gravitational Lensing Experiment) project reveals periods of time in which quasi-periodic optical flares occur at intervals of ∼21.5 d. The X-ray data obtained from the S-CUBED project reveal a very soft spectrum, too soft to be that from accretion on to a neutron star or black hole. It is suggested here that this is a rarely identified Be star–white dwarf binary in the SMC.

Description: Gravitational microlensing can detect isolated stellar-mass black holes (BHs), which are believed to be the dominant form of Galactic BHs according to population synthesis models. Previous searches for BH events in microlensing data focused on long time-scale events with significant microlensing parallax detections. Here we show that, although BH events preferentially have long time-scales, the microlensing parallax amplitudes are so small that in most cases the parallax signals cannot be detected statistically significantly. We then identify OGLE-2006-BLG-044 to be a candidate BH event because of its long time-scale and small microlensing parallax. Our findings have implications to future BH searches in microlensing data.

Description: Recent application of Fourier transform near infra-red spectroscopy (FT-NIRS) to predict age in fish otoliths has gained attention among fisheries managers as a potential alternative to costly production ageing of managed species. We assessed the age prediction capability of FT-NIRS scans in whole otoliths from red snapper, Lutjanus campechanus, collected from the US Gulf of Mexico and US Atlantic Ocean (South Atlantic). Otoliths were scanned with an FT-NIR spectrometer and resulting spectral signatures were regressed with traditionally estimated ages via partial least squares regression to produce calibration models, which were validated for predictive capability against test sets of otoliths. Calibration models successfully predicted age with R2 ranging 0.94–0.95, mean squared error ≤1.8 years, and bias 31 years were not well predicted, possibly due to light attenuation in the thickest otoliths. Our results suggest that FT-NIRS can improve efficiency in production ageing for fisheries management while maintaining data quality standards.

Description: Replacive symplectites (vermicular intergrowths of two or more minerals) are an important feature of layered igneous intrusions, recording evidence of late-stage reactions between interstitial liquid and crystals. They are common throughout the Layered Series of the 564 Ma Sept Iles layered intrusion in Quebec, Canada, and fall into three types: oxy-symplectites, ‘Type I’ symplectites, and ‘Type II’ symplectites. Oxy-symplectites are comprised of magnetite and orthopyroxene, nucleate on olivine primocrysts, and form via the reaction Olivine + O2 → Orthopyroxene + Magnetite; Type I symplectites (of which there are 3 distinct categories) are comprised of anorthitic plagioclase with pyroxene, amphibole, or olivine vermicules, grow from primocryst oxide grains, and replace primary plagioclase; and Type II symplectites (of which there are 2 distinct categories) are comprised of anorthitic plagioclase with orthopyroxene ± amphibole vermicules, grow from primocryst olivine grains, and replace primocryst plagioclase. Rare symplectites composed of biotite and plagioclase are also present. Symplectite growth occurred at 700-1030 °C with pressure constraints of 1-2 kbar. We propose that Type I symplectites, and some Type II symplectites, formed from interaction of primocrysts with residual Fe-rich liquid as a consequence of differential loss of an immiscible Si-rich liquid conjugate from the crystal mush. However, redistribution and concentration of hydrous fluids in incompletely solidified rock, or an increase in water activity of the interstitial melt, may be more plausible processes responsible for the formation of replacive symplectites comprising abundant hydrous mineral assemblages.

Description: This article investigates the diet of the snow crab (Chionoecetes opilio) and its feeding intensity in the Barents Sea. Data show that snow crab has a diverse diet that includes almost all types of benthic invertebrates living in the Barents Sea. There are differences between the diets of females and males and of juveniles and adults. Juveniles and females typically occupy shallow areas with communities of bivalve molluscs, while males typically live deeper on slopes and depressions where polychaetes and crustaceans are the most abundant groups. Stomach contents were analysed to determine the species composition and frequency of occurrence of various benthic taxa. Consumption of food was estimated and compared with data from the Russian seas of the Pacific region. The total annual consumption of macrozoobenthos by snow crab was calculated in accordance with its current distribution in the Barents Sea. Snow crab consumes at least 30 000 tonnes of benthos annually, which amounts to 0.1–0.2% of the total macrozoobenthic biomass in the investigated area. The population of snow crab causes the largest impact on the benthic communities in the northeastern part of the Barents Sea and near the south side of the Novaya Zemlya archipelago.

Description: Until the late 19th century, extensive beds of flat oyster Ostrea edulis populated the Central North Sea, which have vanished after intensive fisheries. At present, various initiatives are being carried out to investigate the potential to restore this former key species in the area. This historical ecological study contributes by delineating the former oyster bed area and through an assessment of its limits against known gradients in the North Sea. Extensive data from historical maps, texts, and ship-based surveys were used to synthesize our knowledge on the former beds. It was revealed that the area with oyster beds covered ∼6.2% of the total North Sea bottom, with a delineation that could partly be explained by hydrodynamic and temperature gradients. The position and extent of the area are notably different from the area that is used in recent feasibility studies on the restoration of North Sea oyster beds. The offshore oysters lived on muddy sand in relatively cold conditions, and there are several indications that their reproductive rate was low. The apparent disappearance of cold water adapted flat oysters will challenge restoration projects. This study provides indispensable information for the future restoration of flat oyster beds in the North Sea.

Description: We present a sub-100 pc-scale analysis of the CO molecular gas emission and kinematics of the gravitational lens system SDP.81 at redshift 3.042 using Atacama Large Millimetre/submillimetre Array (ALMA) science verification data and a visibility-plane lens reconstruction technique. We find clear evidence for an excitation-dependent structure in the unlensed molecular gas distribution, with emission in CO (5–4) being significantly more diffuse and structured than in CO (8–7). The intrinsic line luminosity ratio is r 8–7/5–4  = 0.30 ± 0.04, which is consistent with other low-excitation starbursts at z  ~ 3. An analysis of the velocity fields shows evidence for a star-forming disc with multiple velocity components that is consistent with a merger/post-coalescence merger scenario, and a dynamical mass of M (〈1.56 kpc) = 1.6 ± 0.6  x  10 10 M . Source reconstructions from ALMA and the Hubble Space Telescope show that the stellar component is offset from the molecular gas and dust components. Together with Karl G. Jansky Very Large Array CO (1–0) data, they provide corroborative evidence for a complex ~2 kpc-scale starburst that is embedded within a larger ~15 kpc structure.

Description: Regardless of the physical origin of stellar magnetic fields – fossil or dynamo induced - an inclination angle between the magnetic and rotation axes is very often observed. Absence of observational evidence in this direction in the solar case has led to generally assume that its global magnetic field and rotation axes are well aligned. We present the detection of a monthly periodic signal of the photospheric solar magnetic field at all latitudes, and especially near the poles, revealing that the main axis of the Sun's magnetic field is not aligned with the surface rotation axis. This result reinforces the view of our Sun as a common intermediate-mass star. Furthermore, this detection challenges and imposes a strong observational constraint to modern solar dynamo theories.

Description: We use the ‘Evolution and Assembly of GaLaxies and their Environments’ ( eagle ) suite of hydrodynamical cosmological simulations to measure offsets between the centres of stellar and dark matter components of galaxies. We find that the vast majority (〉95 per cent) of the simulated galaxies display an offset smaller than the gravitational softening length of the simulations (Plummer-equivalent  = 700 pc), both for field galaxies and satellites in clusters and groups. We also find no systematic trailing or leading of the dark matter along a galaxy's direction of motion. The offsets are consistent with being randomly drawn from a Maxwellian distribution with  ≤ 196 pc. Since astrophysical effects produce no feasible analogues for the $1.62^{+0.47}_{-0.49}$  kpc offset recently observed in Abell 3827, the observational result is in tension with the collisionless cold dark matter model assumed in our simulations.

Description: The solar wind magnetic field contains rotations at a broad range of scales, which have been extensively studied in the magnetohydrodynamics range. Here, we present an extension of this analysis to the range between ion and electron kinetic scales. The distribution of rotation angles was found to be approximately lognormal, shifting to smaller angles at smaller scales almost self-similarly, but with small, statistically significant changes of shape. The fraction of energy in fluctuations with angles larger than α was found to drop approximately exponentially with α, with e-folding angle 9.8° at ion scales and 0 $_{.}^{\circ}$ 66 at electron scales, showing that large angles (α 〉 30°) do not contain a significant amount of energy at kinetic scales. Implications for kinetic turbulence theory and the dissipation of solar wind turbulence are discussed.

Description: Successful implementation of Ecosystem-Based Fisheries Management (EBFM) requires appropriate action as informed by reference points in an ecosystem context. Thresholds in the response of ecological indicators to system drivers have been suggested as reference points for EBFM, though the management performance of these indicators and possible values for their reference points have not been widely evaluated. We used Management Strategy Evaluation to test the performance of control rules that used ecological indicators to adjust the advice from single-species stock assessments, using the Georges Bank finfish fishery as a case study. We compare the performance of control rules that used ecological indicators to that of single-species F MSY control rules when the system dynamics were governed by the same multispecies population model. Control rules that used indicator-based reference points were able to perform better against catch and biodiversity objectives than when harvests were based on single-species advice alone. Indicators and values for reference points associated with good performance varied depending on the management objective. We quantified tradeoffs between total catch, biodiversity, and interannual variability in catch, noting that it was possible in some instances to achieve higher than average biodiversity while maintaining high catches using indicator-based control rules. While improved performance was noted using ecological indicators, outcomes were variable, and the gains in performance obtained may be similar to alternative methods of implementing precaution in single-species fishery control rules.

Description: Climate change and fishing can have major impacts on the distribution of natural marine resources. Climate change alters the distribution of suitable habitat, forcing organisms to shift their range or attempt to survive under suboptimal conditions. Fishing reduces the abundance of marine populations and truncates their age structure leading to range contractions or shifts. Along the east coast of the United States, there have been major changes in fish populations due to the impacts of fishing and subsequent regulations, as well as changes in the climate. Black sea bass, scup, summer flounder, and winter flounder are important commercial and recreational species, which utilize inshore and offshore waters on the northeast shelf. We examined the distributions of the four species with the Northeast Fisheries Science Center trawl surveys to determine if the along-shelf centres of biomass had changed over time and if the changes were attributed to changes in temperature or fishing pressure through changes in abundance and length structure. Black sea bass, scup, and summer flounder exhibited significant poleward shifts in distributions in at least one season while the Southern New England/Mid-Atlantic Bight stock of winter flounder did not shift. Generalized additive modelling indicated that the changes in the centres of biomass for black sea bass and scup in spring were related to climate, while the change in the distribution of summer flounder was largely attributed to a decrease in fishing pressure and an expansion of the length–age structure. While the changes in ocean temperatures will have major impacts on the distribution of marine taxa, the effects of fishing can be of equivalent magnitude and on a more immediate time scale. It is important for management to take all factors into consideration when developing regulations for natural marine resources.

Description: Many snow crab fisheries have fluctuated widely over time in a quasi-cyclic way due to highly variable recruitment. The causes of this variability are still debated. Bottom-up processes related to climate variability may strongly affect growth and survival during early life, whereas top-down predator effects may be a major source of juvenile mortality. Moreover, intrinsic density-dependent processes, which have received much less attention, are hypothetically responsible for the cycles in recruitment. This study explored how climate, larval production, intercohort cannibalism and groundfish predation may have affected recruitment of early juvenile snow crab in the northwest Gulf of St Lawrence (eastern Canada) over a period of 23 years. Abundance of early juvenile snow crabs (2.5–22.9 mm in carapace width), representing the first 3 years of benthic life, came from an annual trawl survey and was used to determine cohort strength. Analyses revealed a cyclic pattern in abundance of 0 + crabs that may arise from cohort resonant effects. This pattern consisted of three recruitment pulses but was reduced to two pulses by age 2 + , while the interannual variability of cohort strength was dampened. This reconfiguration of the earliest recruitment pattern was dictated primarily by bottom water temperature and cannibalism, which progressively overruled the pre-settlement factors of larval production and surface water temperature that best explained abundance of 0 + crabs. The results strongly suggest that bottom-up and density-dependent processes prevail over top-down control in setting the long-term trends and higher-frequency oscillations of snow crab early recruitment patterns.

Description: Fisheries biology encompasses a tremendous diversity of research questions, methods, and models. Many sub-fields use observational or experimental data to make inference about biological characteristics that are not directly observed (called "latent states"), such as heritability of phenotypic traits, habitat suitability, and population densities to name a few. Latent states will generally cause model residuals to be correlated, violating the assumption of statistical independence made in many statistical modelling approaches. In this exposition, we argue that mixed-effect modelling (i) is an important and generic solution to non-independence caused by latent states; (ii) provides a unifying framework for disparate statistical methods such as time-series, spatial, and individual-based models; and (iii) is increasingly practical to implement and customize for problem-specific models. We proceed by summarizing the distinctions between fixed and random effects, reviewing a generic approach for parameter estimation, and distinguishing general categories of non-linear mixed-effect models. We then provide four worked examples, including state-space, spatial, individual-level variability, and quantitative genetics applications (with working code for each), while providing comparison with conventional fixed-effect implementations. We conclude by summarizing directions for future research in this important framework for modelling and statistical analysis in fisheries biology.

Description: While the impact of environmental forcing on recruitment variability in marine populations remains largely elusive, studies spanning large spatial areas and many stocks are able to identify patterns common to different regions and species. In this study, we investigate the effects of the environment on the residuals of a Ricker stock–recruitment (SR) model, used as a proxy of prerecruits' survival, of 18 assessed stocks in the Baltic and North Seas. A probabilistic principal components (PCs) analysis permits the identification of groups of stocks with shared variability in the prerecruits' survival, most notably a group of pelagics in the Baltic Sea and a group composed of gadoids and herring in the North Sea. The first two PCs generally grouped the stocks according to their localizations: the North Sea, the Kattegat–Western Baltic, and the Baltic Sea. This suggests the importance of the local environmental variability on the recruitment strength. Hence, the prerecruits' survival variability is studied according to geographically disaggregated and potentially impacting abiotic or biotic variables. Time series (1990–2009) of nine environmental variables consistent with the spawning locations and season for each stock were extracted from a physical–biogeochemical model to evaluate their ability to explain the survival of prerecruits. Environmental variables explained 〉70% of the survival variability for eight stocks. The variables water current, salinity, temperature, and biomass of other fish stocks are regularly significant in the models. This study shows the importance of the local environment on the dynamics of SR. The results provide evidence of the necessity of including environmental variables in stock assessment for a realistic and efficient management of fisheries.

Description: Ecosystem-based fisheries management seeks to consider trade-offs among management objectives for interacting species, such as those that arise through predator–prey linkages. In particular, fisheries-targeting forage fish (small and abundant pelagic fish) might have a detrimental effect on fisheries-targeting predators that consume them. However, complexities in ecological interactions might dampen, negate, or even reverse this trade-off, because small pelagic fish can be important predators on egg stages of piscivorous fish. Further, the strength of this trade-off might depend on the extent to which piscivorous fish targeted by fisheries regulate forage species productivity. Here, we developed a novel delay-differential bioeconomic model of predator–prey and fishing dynamics to quantify how much egg predation or weak top-town control affects the strength of trade-off between forage and piscivore fisheries, and to measure how ecological interactions dictate policies that maximize steady-state profits. We parameterized the model based on ecological and economic data from the North Sea Atlantic cod ( Gadus morhua ) and Atlantic herring ( Clupea harengus ). The optimal policy was very sensitive to the ecological interactions (either egg predation or weak top-down control of forage by predators) at relatively low forage prices but was less sensitive at high forage fish prices. However, the optimal equilibrium harvest rates on forage and piscivores were not substantially different from what might be derived through analyses that did not consider species interactions. Applying the optimal multispecies policy would produce substantial losses (〉25%) in profits in the piscivore fishery, and the extent of loss was sensitive to ecological scenarios. While our equilibrium analysis is informative, a dynamic analysis under similar ecological scenarios is necessary to reveal the full economic and ecological benefits of applying ecosystem-based fishery management policies to predator–prey fishery systems.

Description: Leptocephali, the larvae of eels, grow to large sizes and are widely distributed in tropical and subtropical oceans. Their role in oceanic food webs is poorly known because they are rarely reported as food items in fish stomach content studies. Data from 13 years of research on the trophic dynamics of Pacific Ocean predatory fish indicate that among 8746 fish of 76 species/taxa (33 families) that had been feeding, only 16 fish of 6 species had remains of 34 leptocephali in their stomachs. Only 0.013% of the 256 308 total prey items were leptocephalus larvae, and 0.03% of the total prey items were juvenile or adult eels (mostly snipe eels: Nemichthyidae). There were 10 fish of 2 species of lancetfish ( Alepisaurus spp., n = 152), 2 rainbow runners ( Elagatis bipinnulata , n = 222), and 2 yellowfin tuna ( Thunnus albacares , n = 3103) that had leptocephali in their stomach contents, but all except one T. albacares (contained 15 leptocephali) had each eaten ≤3 leptocephali. A swallower, Pseudoscopelus sp., and a frigate tuna, Auxis thazard , had eaten single leptocephali. Twenty-eight bigeye tuna, Thunnus obesus , had eaten 76 juvenile/adult nemichthyid or serrivomerid eels. A literature survey found that only 15 out of 75 examined publications listed leptocephali in the stomach contents of a total of 6 species out of ~ 42 300 predatory fish of 40 species. The transparency of leptocephali and their apparent mimicry of gelatinous zooplankton could contribute to lower rates of predation. Their soft bodies likely digest rapidly, so although this study and existing literature indicate that leptocephali sometimes contribute to predatory fish diets, particularly for fish that do not exclude gelatinous prey types, and fish with low digestion rates in their stomachs such as lancetfish, their levels of contribution to fish diets and the impacts of predators on eel recruitment remain uncertain.

Description: Effective individual transferable quotas (ITQ) systems rebuild stocks and allow transfer of quotas to more efficient operators. This process requires functional markets for both quota sales and temporary quota leases. These markets are expected to respond to changes in economic rent from the fishery, which is influenced by stock abundance and the international rock lobster price. This research used multistate Markov modelling and Granger causality test to examine changes in the permanent and temporary quota trade in the Tasmanian rock lobster fishery quota market, during periods of both increasing and decreasing stock abundance. The permanent quota trade market was more active during the period of stock growth, while the quota lease market was active in both periods of stock growth and decline. In contrast to theoretical trends in ITQ fisheries, trades in both markets were not linked to the technical efficiency (i.e. catching capability) of operators, but were more driven by the quota owners' financial capacity (i.e. number of owned quotas). Prolonged and unexpected stock decline affected the quota market so that it deviated from the theoretical pattern of ITQ fisheries. Operators previously active in the market reduced their activity, while smaller operators and firms that previously had not traded became more active, so the fleet expanded with smaller operators entering.

Description: Jellyfish disruption of fisheries has been described in some coastal systems, but few thorough investigations have been conducted. To ascertain the economic impact and trend of jellyfish blooms in the Northern California Current (NCC), we mailed surveys to resident commercial shrimpers, salmon trollers, rockfish (blue, black), and groundfish fishers ( n = 872). We asked fishers to estimate the damages caused by jellyfish—including costs of relocating to avoid blooms, lost fishing time, time lost to bycatch sorting, fish depreciation, and gear damage. Of the total respondents ( n = 111), 67% reported that jellyfish reduce their seasonal revenue, but the degree of impact ranged considerably by fishery and location. Highest jellyfish nuisance corresponded to regions with the most salmon trolling effort. Using the mean revenue losses provided by respondents, we estimate that the combined economic impact of jellyfish on Oregon's salmon and pink shrimp fishers was over $650 000 in peak jellyfish season (June–September) in 2012. Fishers reported that jellyfish biomass varies annually, but most respondents (51%) reported observing no appreciable change in jellyfish populations in the last 5 years. Since economic impact analyses have been conducted primarily in areas with anomalous, high-density blooms, data from the NCC, which is not known to be experiencing increases in jellyfish abundance, provides baseline information on the socio-economic impact of jellyfish blooms in this region. In addition, the finding that jellyfish impact hook and line fisheries—not solely net fisheries—has implications for many other regions where fishers employ this gear type.

Description: Odontocete depredation on longlines involves socioeconomic and conservation issues with significant losses for fisheries and potential impacts on wild populations of depredating species. As technical solutions to this conflict are limited and difficult to implement, this study aimed to identify fishing practices that could reduce odontocete depredation, with a focus on killer whales (Orcinus orca) interacting with Patagonian toothfish (Dissostichus eleginoides) longliners off the Crozet islands. Data collected by fishery observers from 6013 longline sets between 2003 and 2013 allowed us to statistically detect the significant influence of five operational variables using GLMMs. The probability of interactions between vessels and killer whales was decreased by (i) the number of vessels operating simultaneously in the area: the limited number of depredating killer whales may induce a dilution effect with increased fleet size, and (ii) depth of longline sets: vessels operating in shallow waters may be more accessible to whales that are initially distributed on peri-insular shelves. The cpue was negatively influenced by (iii) length of longlines: longer sets may provide killer whales access to a greater proportion of hooked fish per set, and positively influenced by (iv) hauling speed: increased speed may shorten the time during which toothfish are accessible to whales during hauling. The time it takes for killer whales to reach vessels was positively correlated to (v) the distance travelled between longline sets with an estimated threshold of 100 km beyond which whales seem to temporarily lose track of vessels. These findings provide insightful guidelines about what fishing strategy to adopt given these variables to reduce killer whale depredation here and in similar situations elsewhere. To a greater extent, this study is illustrative of how collaborative work with fishermen in a fully controlled fishery framework may lead to the definition of cost-limited and easy-to-implement mitigation solutions when facing such human-wildlife conflict.

Description: In Alaskan waters, depredation on sablefish longline gear by sperm whales increases harvesting cost, negatively biases stock assessments, and presents a risk of entanglement for whales. The Southeast Alaska Sperm Whale Avoidance Project (SEASWAP), a collaborative effort involving industry, scientists, and managers, since 2003 has undertaken research to evaluate depredation with a goal of recommending measures to reduce interactions. Prior to 2003, little was known about sperm whale distribution and behaviour in the Gulf of Alaska (GOA). Although fishers were reporting increasing interactions, the level of depredation varied with no apparent predictor of occurrence across vessels. Between 2003 and 2007, fishers were provided with fishery logbooks and recorded information on whale behaviour, whale presence and absence, during the set, soak, and haul for 319 sets in the GOA. Data were evaluated for a vessel, area, and seasonal (month) effect in the presence and absence of sperm whales. Using catch per unit effort ( cpue ) as a metric, in kg/100 hooks, results indicated that depredation depended on both the vessel and the area. More whales associated with vessels from April to August. Sperm whales were also likely to be present when cpue was high, revealing that whales and fishers both knew the most productive fishing areas, but confounding the use of cpue as a metric for depredation. Using a Bayesian mark-recapture analysis and the sightings histories of photo-identified whales, an estimated $$\hat{N}=135$$ (95% CI 124, 153) sperm whales were associating with vessels in 2014. A spatial model was fitted to 319 longline sets and quantified a 3% loss in cpue , comparable to other global studies on sperm whale depredation. Through all phases of SEASWAP, our understanding of depredation has gained significantly. This successful collaboration should be considered as a model to create partnerships and build collaborations between researchers and fisherpeople encountering marine mammal interactions with fishing gear.

Description: This paper provides a synthesis of results obtained as part of a long-term collaborative study involving biologists, fishers, and resource managers—centring on the occurrence of killer whales in the Crozet Archipelago before and after the implementation of a demersal longline fishery for Patagonian toothfish. Depredation behaviour was reported as soon as the fishery was initiated, with dramatic effects on both the demographic trajectories of the killer whales and on the amount of fish lost by the fishers. Killer whales interacting with the fishery exhibited very high mortality rates when illegal fishing took place, while killer whales not interacting were unaffected. However, after illegal fishing ended, killer whales interacting with the fishery exhibited both higher fecundity and survival rates compared with killer whales not interacting. Since whales typically removed fish entirely from the hooks, an adapted methodology that did not rely on determining the number of damaged fish was developed to estimate depredation rates. In the Crozet EEZ over a 10-year period, 33.9% of the total amount of Patagonian toothfish caught, representing a total of 28 million , was estimated to be lost due to the combined effects of killer whale and sperm whale depredation. In an effort to reduce depredation losses, modifications to fishing methods, such as changing the fishing season, changing fishing areas when exposed to depredation and changing longline length and hauling speed were successfully tested. Acoustic deterrent devices were ineffective in deterring killer whales from depredating longlines. Alternative fishing gears, such as fish pots, were also tested. However, while providing encouraging results regarding the suppression of depredation and seabird bycatch, fish pots were not efficient enough to sustain an economically viable fishery. In conclusion, we discuss how the findings of this comprehensive study can be used elsewhere in fisheries confronted with depredation.

Description: We report the broad-band spectral properties of the X-ray pulsar Cep X-4 by using a Suzaku observation in 2014 July. The 0.8–70 keV spectrum was found to be well described by three continuum models – Negative and Positive power-law with Exponential cut-off (NPEX), high-energy cut-off power-law and CompTT models. Additional components such as a cyclotron line at ~28 keV and two Gaussian components for iron lines at 6.4 and 6.9 keV were required in the spectral fitting. Apart from these, an additional absorption feature at ~45 keV was clearly detected in residuals obtained from the spectral fitting. This additional feature at ~45 keV was clearly seen in phase-resolved spectra of the pulsar. We identified this feature as the first harmonic of the fundamental cyclotron line at ~28 keV. The ratio between the first harmonic and fundamental line energies (1.7) was found to be in disagreement with the conventional factor of 2, indicating that the heights of line-forming regions are different or viewed at larger angles. The phase-resolved spectroscopy of the fundamental and first harmonic cyclotron lines shows significant pulse-phase variation of the line parameters. This can be interpreted as the effect of viewing angle or the role of complicated magnetic field of the pulsar.

Description: The spin-down of a neutron star, e.g. due to magneto-dipole losses, results in compression of the stellar matter and induces nuclear reactions at phase transitions between different nuclear species in the crust. We show that this mechanism is effective in heating recycled pulsars, in which the previous accretion process has already been compressing the crust, so it is not in nuclear equilibrium. We calculate the corresponding emissivity and confront it with available observations, showing that it might account for the likely thermal ultraviolet emission of PSR J0437–4715.

Description: New insights into the formation of interstellar formamide, a species of great relevance in prebiotic chemistry, are provided by electronic structure and kinetic calculations for the reaction NH 2 + H 2 CO -〉 NH 2 CHO + H. Contrarily to what previously suggested, this reaction is essentially barrierless and can, therefore, occur under the low temperature conditions of intestellar objects thus providing a facile formation route of formamide. The rate coefficient parameters for the reaction channel leading to NH 2 CHO + H have been calculated to be A = 2.6 x 10 –12  cm 3  s –1 , β = –2.1 and = 26.9 K in the range of temperatures 10–300 K. Including these new kinetic data in a refined astrochemical model, we show that the proposed mechanism can well reproduce the abundances of formamide observed in two very different interstellar objects: the cold envelope of the Sun-like protostar IRAS16293–2422 and the molecular shock L1157-B2. Therefore, the major conclusion of this Letter is that there is no need to invoke grain-surface chemistry to explain the presence of formamide provided that its precursors, NH 2 and H 2 CO, are available in the gas phase.

Description: The Matachewan Large Igneous Province (LIP) is interpreted to have formed during the early stages of mantle plume-induced continental break-up in the early Proterozoic. When the Matachewan LIP is reconstructed to its original configuration with units from the Superior Craton and other formerly adjacent blocks (Karelia, Kola, Wyoming and Hearne), the dyke swarms, layered intrusions and flood basalts, emplaced over the lifetime of the province, form one of the most extensive magmatic provinces recognized in the geological record. New geochemical data allow, for the first time, the Matachewan LIP to be considered as a single, coherent entity and show that Matachewan LIP rocks share a common tholeiitic composition and trace element geochemistry, characterized by enrichment in the most incompatible elements and depletion in the less incompatible elements. This signature, ubiquitous in early Proterozoic continental magmatic rocks, may indicate that the Matachewan LIP formed through contamination of the primary magmas with lithospheric material or that the early Proterozoic mantle had a fundamentally different composition from the modern mantle. In addition to the radiating geometry of the dyke swarms, a plume origin for the Matachewan LIP is consistent with the geochemistry of some of the suites; these suites are used to constrain a source mantle potential temperature of c. 1500–1550°C. Comparison of these mantle potential temperatures with estimated temperatures for the early Proterozoic upper mantle indicates that they are consistent with a hot mantle plume source for the magmatism. Geochemical data from coeval intrusions suggest that the plume head was compositionally heterogeneous and sampled material from both depleted and enriched mantle. As has been documented with less ancient but similarly vast LIPs, the emplacement of the Matachewan LIP probably had a significant impact on the early Proterozoic global environment. Compilation of the best age estimates for various suites shows that the emplacement of the Matachewan LIP occurred synchronously with the Great Oxidation Event. We explore the potential for the eruption of this LIP and the emission of its associated volcanic gases to have been a driver of the irreversible oxygenation of the Earth.

Description: Olivine major and trace element compositions from 12 basalts from the southern Payenia volcanic province in Argentina have been analyzed by electron microprobe and laser ablation inductively coupled plasma mass spectrometry. The olivines have high Fe/Mn and low Ca/Fe and many fall at the end of the global olivine array, indicating that they were formed from a pyroxene-rich source distinct from typical mantle peridotite. The olivines with the highest Fe/Mn have higher Zn/Fe, Zn and Co and lower Co/Fe than the olivines with lower Fe/Mn, also suggesting contributions from a pyroxene-rich source. Together with whole-rock radiogenic isotopes and elemental concentrations, the samples indicate mixing between two mantle sources: (1) a pyroxene-rich source with EM-1 ocean island basalt type trace element and isotope characteristics; (2) a peridotitic source with more radiogenic Pb that was metasomatized by subduction-zone fluids and/or melts. The increasing contributions from the pyroxene-rich source in the southern Payenia basalts are correlated with an increasing Fe-enrichment, which caused the olivines to have lower forsterite contents at a given Ni content. Al-in-olivine crystallization temperatures measured on olivine–spinel pairs are between 1155 and 1243°C and indicate that the magmas formed at normal upper mantle (asthenospheric) temperatures of ~1350°C. The pyroxene-rich material is interpreted to have been brought up from the deeper parts of the upper mantle by vigorous asthenospheric upwelling caused by break-off of the Nazca slab south of Payenia during the Pliocene and roll-back of the subducting slab beneath Payenia. The pyroxene-rich mantle mixed with peridotitic metasomatized South Atlantic mantle in the mantle wedge beneath Payenia.

Description: To reconstruct the magmatic–hydrothermal processes leading to porphyry Mo ore formation at the Climax Mo mine, Colorado, four magma units that were emplaced before, during and shortly after the mineralization events were investigated: (1) a pre-mineralization white dike of the Alma district; (2) the syn-mineralization Chalk Mountain Rhyolite; (3) a late- to post-mineralization rhyolite porphyry dyke; (4) a mafic enclave within the productive Bartlett stock. Melt inclusions, mineral inclusions and fluid inclusions in quartz phenocrysts were investigated by means of laser ablation inductively coupled plasma mass spectrometry, electron microprobe and microthermometry. Based on melt inclusion data both the Chalk Mountain Rhyolite and the rhyolite porphyry were ~10 times more fractionated than average granite and show geochemical characteristics of topaz rhyolites. They were saturated in magnetite, Mn-rich ilmenite, fluorite, aeschynite, monazite, pyrrhotite and thorite, and crystallized predominantly at 710–730°C, 1·2–2·6 kbar and log f O 2 FMQ + 2·2 (where FMQ is fayalite–magnetite–quartz). The silicate melt of the Chalk Mountain Rhyolite contained 3·5 ± 0·4 wt % F, 0·09 ± 0·03 wt % Cl, ≥ 3·0 wt % H 2 O, 15–90 µg g –1 Cs, 500–1500 µg g –1 Rb and 5–7 µg g –1 Mo, whereas that of the rhyolite porphyry contained 1·1 ± 0·3 wt % F and 4·9 ± 1·2 wt % H 2 O, but otherwise had a virtually identical major and trace element composition. The fluid exsolving from the latter melt had a bulk salinity of 10 ± 2 wt % NaCl equiv and contained of the order of 100 µg g –1 Mo. After emplacement of the Chalk Mountain Rhyolite magma at subvolcanic levels, extremely fractionated silicate melts coexisting with hypersaline brines (salt melts) and low-density vapor percolated at near-solidus conditions through the rock. These silicate melts contained 6·6 ± 0·4 wt % F, ≥ 7·5 ± 0·6 wt % H 2 O, 0·51 ± 0·05 wt % Cl, and up to 0·5 wt % Cs and 100 µg g –1 Mo, whereas the hypersaline brines contained 1–2 wt % Cs and 0·3–0·6 wt % Mo. However, owing to their negligible masses these liquids are unlikely to have played a major role in the mineralization process. The majority of Mo in the Climax deposit appears to have been derived from melts containing 5–7 µg g –1 Mo and bulk fluids containing ~100 µg g –1 Mo. These concentrations are similar to those found in similarly fractionated melts and fluids in barren and sub-economically mineralized intrusions. However, whereas in the latter intrusions fractionated melts occurred in a rather dispersed state, they seem to have been present as large, coherent masses in the apical parts of Climax-type porphyry Mo-forming magma systems. Efficient segregation of fractionated melts and fluids into the top of mineralizing magma chambers appears to have been promoted by high fluorine concentrations in the silicate melt, which was partly a primary feature, and partly an indirect consequence of other characteristics of within-plate magmatism.

Description: The Skaergaard intrusion, Greenland, is the type locality for Skaergaard-type mineralizations. Mineralization levels are perfectly concordant with igneous layering, up to 5 m thick, internally fractionated, and contain crystallized sulphide droplets and precious metal alloys, sulphides, arsenides and telluride. Immiscible Cu-rich sulphide droplets, formed in a mush zone below the roof, scavenged precious metals. They were subsequently dissolved and transported to the floor in late-formed, immiscible, Fe-rich mush melts. Mineralized stratigraphic intervals of floor gabbro formed in ‘proto-macrolayers‘, owing to local sulphide saturation in melt concentrated between floating plagioclase and sinking clinopyroxene. The floor mineralization is divided into four stratigraphic sections. Formation of the Lower Platinum Group Element Mineralization (LPGEM) involved: (1) crystallization of the bulk liquid liquidus paragenesis and in situ fractionation; (2) sulphide saturation and formation of sulphide droplets in melt in the upper part of ‘proto-macrolayers‘. After further in situ fractionation, the following steps occurred: (3) the onset of silicate–silicate immiscibility and the consequent loss of buoyant and immiscible Si-rich melt; (4) dissolution of unprotected droplets of sulphide melt present in the Fe-rich mush melt; (5) compaction-driven upwards loss of residual mush melt enriched in, for example, Au. The LPGEM preserves upward increasing bulk Pd/Pt (~6–13) owing to a continued supply of PGE and Au, with high Pd/Pt. The further development of the LPGEM ceased as the supply of precious metals to the floor waned. The Upper PGE Mineralization (UPGEM) subsequently formed from precious metals recycled in the floor. The UPGEM is characterized by increasing Au substitution in PGE phases, and a decrease in total PGE and Pd/Pt owing to upward fractionation in migrating mush melts and exhaustion of Pd and Pt. An upper Au-rich mineralization level (UAuM) was caused by late remobilization of Au and deposition on grain boundaries in fully crystallized gabbro. Cu concentrations (~150 ppm) are not correlated with PGE and Au. Repeated Cu mineralization levels (CuM), attaining 〉1000 ppm, occur above the Au levels, caused by local mush layer sulphide saturation. PGE, Au and Cu distributions in the floor mineralization reflect sub-liquidus, but supra-solidus, processes and reactions in mushes at the roof, wall and floor. Constraints provided by a new model for the mineralization provide the basis for re-evaluation of the solidification processes in the Skaergaard intrusion. We have identified the importance of extensive in situ fractionation and intrusion-wide elemental redistributions in immiscible Fe- and Si-rich silicate melts. Our model characterizes the floor cumulates as bulk liquid orthocumulates containing an upwards-increasing proportion crystallized from Fe-rich, immiscible mush melt. The roof-rocks are complementary to the floor, with downwards increasing proportions crystallized from the conjugate Si-rich melt. Petrographic observations and the relative timing of crystallization support the hypothesis that crystallization was restricted to marginal mush zones. Bulk melt remaining in the magma chamber evolved not, as generally assumed, as a result of loss of crystals grown from the bulk melt, but as the consequence of mixing with recycled and evolved melt expelled from the mush by compaction. Redistribution of Fe in immiscible melts may be common to mafic intrusions and puts into question the validity of petrogenetic modelling of bulk liquids in mafic intrusions based only on consideration of floor cumulates.

Description: We have determined experimentally the hydrous phase relations and trace element partitioning behaviour of ocean floor basalt protoliths at pressures and temperatures (3 GPa, 750–1000°C) relevant to melting in subduction zones. To avoid potential complexities associated with trace element doping of starting materials we have used natural, pristine mid-ocean ridge basalt (MORB from Kolbeinsey Ridge) and altered oceanic crust (AOC from Deep Sea Drilling Project leg 46, ~20°N Atlantic). Approximately 15 wt % water was added to starting materials to simulate fluid fluxing from dehydrating serpentinite underlying the oceanic crust. The vapour-saturated solidus is sensitive to basalt K 2 O content, decreasing from 825 ± 25°C in MORB (~0·04 wt % K 2 O) to 750°C in AOC (~0·25 wt % K 2 O). Textural evidence indicates that near-solidus fluids are sub-critical in nature. The residual solid assemblage in both MORB and AOC experiments is dominated by garnet and clinopyroxene, with accessory kyanite, epidote, Fe–Ti oxide and rutile (plus quartz–coesite, phengite and apatite below the solidus). Trace element analyses of quenched silica-rich melts show a strong temperature dependence of key trace elements. In contrast to the trace element-doped starting materials of previous studies, we do not observe residual allanite. Instead, abundant residual epidote provides the host for thorium and light rare earth elements (LREE), preventing LREE from being released (LREE 〈3 ppm at 750–900°C). Elevated Ba/Th ratios, characteristic of many arc basalts, are found to be generated within a narrow temperature field above the breakdown temperature of phengite, but below exhaustion of epidote. Melts with Ba/Th 〉1500 and La/Sm PUM (where PUM indicates primitive upper mantle) ~1, most closely matching the geochemical signal of arc lavas worldwide, were generated from AOC at 800–850°C.

Description: We constrain the physical nature of the magma reservoir and the mechanisms of rhyolite generation at Yellowstone caldera via detailed characterization of zircon and sanidine crystals hosted in three rhyolites erupted during the ( c . 170–70 ka) Central Plateau Member eruptive episode—the most recent post-caldera magmatism at Yellowstone. We present 238 U– 230 Th crystallization ages and trace-element compositions of the interiors and surfaces (i.e. unpolished rims) of single zircon crystals from each rhyolite. We compare these zircon data with 238 U– 230 Th crystallization ages of bulk sanidine separates coupled with chemical and isotopic data from single sanidine crystals. Zircon age and trace-element data demonstrate that the magma reservoir that sourced the Central Plateau Member rhyolites was long-lived (150–250 kyr) and genetically related to the preceding episode of magmatism, which occurred c . 256 ka. The interiors of most zircons in each rhyolite were inherited from unerupted material related to older stages of Central Plateau Member magmatism or the preceding late Upper Basin Member magmatism (i.e. are antecrysts). Conversely, most zircon surfaces crystallized near the time of eruption from their host liquids (i.e. are autocrystic). The repeated recycling of zircon interiors from older stages of magmatism demonstrates that sequentially erupted Central Plateau Member rhyolites are genetically related. Sanidine separates from each rhyolite yield 238 U– 230 Th crystallization ages at or near the eruption age of their host magmas, coeval with the coexisting zircon surfaces, but are younger than the coexisting zircon interiors. Chemical and isotopic data from single sanidine crystals demonstrate that the sanidines in each rhyolite are in equilibrium with their host melts, which considered along with their near-eruption crystallization ages suggests that nearly all Central Plateau Member sanidines are autocrystic. The paucity of antecrystic sanidine crystals relative to antecrystic zircons requires a model in which eruptible rhyolites are generated by extracting melt and zircons from a long-lived mush of immobile crystal-rich magma. In this process the larger sanidine crystals remain trapped in the locked crystal network. The extracted melts (plus antecrystic zircon) amalgamate into a liquid-dominated (i.e. eruptible) magma body that is maintained as a physically distinct entity relative to the bulk of the long-lived crystal mush. Zircon surfaces and sanidines in each rhyolite crystallize after melt extraction and amalgamation, and their ages constrain the residence time of eruptible magmas at Yellowstone. Residence times of the large-volume rhyolites (~40–70 km 3 ) are ≤1 kyr (conservatively 〈6 kyr), which suggests that large volumes of rhyolite can be generated rapidly by extracting melt from a crystal mush. Because the lifespan of the crystal mush that sourced the Central Plateau Member rhyolites is two orders of magnitude longer than the residence time of eruptible magma bodies within the reservoir, it is apparent that the Yellowstone magma reservoir spends most of its time in a largely crystalline (i.e. uneruptible) state, similar to the present-day magma reservoir, and that eruptible magma bodies are ephemeral features.

Description: We report and interpret new geochemical and Pb–Sr–Nd isotopic data from 325 samples of shield, late-shield, postshield, and rejuvenated stage lavas from Kauai and Niihau, the two most northwesterly islands in the Hawaiian island chain. Kauai is unique in the Hawaiian chain in that it exhibits a near-continuous geochemical transition from shield to postshield to rejuvenated stage volcanism between 4·4 and 3·6 Ma and has been continuously active over ~6 Myr. From c . 5·7 to 4·3 Ma, the shield stage of both islands produced tholeiitic basalts typical of other Hawaiian shield volcanoes. The Niihau basalts are more evolved and have high Gd/Yb compared with Kauai, indicating a higher residual garnet content in the source. Both Kauai and Niihau shield basalts have Kea-like trace element ratios, but isotopic ratios are transitional between Kea- and Loa-like compositions. The geochemical similarity of the two shields indicates that mantle sources in different regions of the plume source were similar, and that the 〈2 Ma Loa and Kea trends of the southeastern Hawaiian volcanoes are not observed. More Loa-like compositions are evident in shield lavas from eastern Kauai, where the enhanced Loa composition may reflect melting of low-melting temperature plume components as the island migrates off the hotter, more Kea-like, center of the Hawaiian plume. Postshield lavas and intrusive rocks on both islands are rare: Kauai includes alkalic basalts, hawaiites and mugearites that are isotopically homogeneous and include a significant depleted mantle component compared with the shield basalts, whereas the Niihau late-shield and postshield rocks consist of highly contrasting transitional tholeiites or basanites with variable but shield-like isotopic compositions. The Niihau postshield rocks represent variable, but lower degrees of melting of the shield mantle source. Large volumes of rejuvenated stage lavas cover both islands and also form submarine cone fields, but lava compositions are different. On Kauai, rejuvenated lavas range from melilitite to alkalic basalt with trace element, Nd isotope, and Pb isotope ratios that vary as a function of Th and SiO 2 content. Low-degree (high-Th) melts are dominated by a mixed Kea–Loihi component and high-degree (low-Th) melts include more of a depleted rejuvenated component (DRC) typified by rejuvenated stage lavas and xenoliths from nearby Kaula Island. With the exception of a single basanite, the Niihau rejuvenated stage lavas are uniformly alkalic basalt, with Sr and Ba excesses combined with depleted Th and Nb abundances relative to the light rare earth elements. Rejuvenated stage alkalic basalts from both islands are dominated by contributions from the DRC, which have high Sr/Ce and 87 Sr/ 86 Sr but low 206 Pb/ 204 Pb. The Sr-rich, possibly carbonate-bearing, DRC component may be distributed patchily in the rejuvenated stage mantle source such that, where present, the degree of partial melting was enhanced compared with the degree of partial melting of the Sr-poor, mixed Kea–Loihi component. Given the lack of a hiatus between postshield and rejuvenated stages on Kauai, the rejuvenated mantle source is already able to melt at the tail end of shield stage activity and no secondary melting mechanism is required to explain the rejuvenated stage.

Description: Recent Low-Frequency Array (LOFAR) observations at 115–175 MHz of a field at medium Galactic latitudes (centred at the bright quasar 3C196) have shown striking filamentary structures in polarization that extend over more than 4° across the sky. In addition, the Planck satellite has released full sky maps of the dust emission in polarization at 353 GHz. The LOFAR data resolve Faraday structures along the line of sight, whereas the Planck dust polarization maps probe the orientation of the sky projected magnetic field component. Hence, no apparent correlation between the two is expected. Here we report a surprising, yet clear, correlation between the filamentary structures, detected with LOFAR, and the magnetic field orientation, probed by the Planck satellite. This finding points to a common, yet unclear, physical origin of the two measurements in this specific area in the sky. A number of follow-up multifrequency studies are proposed to shed light on this unexpected finding.

Description: Protoplanetary discs are now routinely observed and exoplanets, after the numerous indirect discoveries, are starting to be directly imaged. To better understand the planet formation process, the next step is the detection of forming planets or of signposts of young planets still in their disc, such as gaps. A spectacular example is the Atacama Large Millimeter/submillimeter Array (ALMA) science verification image of HL Tau showing numerous gaps and rings in its disc. To study the observability of planet gaps, we ran 3D hydrodynamical simulations of a gas and dust disc containing a 5 M J gap-opening planet and characterized the spatial distribution of migrating, growing and fragmenting dust grains. We then computed the corresponding synthetic images for ALMA. For a value of the dust fragmentation threshold of 15 m s –1 for the collisional velocity, we identify for the first time a self-induced dust pile-up in simulations taking fragmentation into account. This feature, in addition to the easily detected planet gap, causes a second apparent gap that could be mistaken for the signature of a second planet. It is therefore essential to be cautious in the interpretation of gap detections.

Description: Recent observations have discovered a number of extremely gas-rich very faint dwarf galaxies possibly embedded in low-mass dark matter haloes. We investigate star formation histories of these gas-rich dwarf (‘almost dark’) galaxies both for isolated and interacting/merging cases. We find that although star formation rates (SFRs) are very low (〈10 –5 M  yr –1 ) in the simulated dwarfs in isolation for the total halo masses ( M h ) of 10 8 -10 9 M , they can be dramatically increased to be ~10 –4 M  yr –1 when they interact or merge with other dwarfs. These interacting faint dwarfs with central compact H ii regions can be identified as isolated emission line dots (‘ELdots’) owing to their very low surface brightness envelopes of old stars. The remnant of these interacting and merging dwarfs can finally develop central compact stellar systems with very low metallicities ( Z /Z  〈 0.1), which can be identified as extremely metal-deficient (‘XMD’) dwarfs. These results imply that although there would exist many faint dwarfs that can be hardly detected in the current optical observations, they can be detected as isolated ELdots or XMD dwarfs, when they interact with other galaxies and their host environments. We predict that nucleated ultrafaint dwarfs formed from the darkest dwarf merging can be identified as low-mass globular clusters owing to the very low surface brightness stellar envelopes.

Description: The BRITE ( BRIght Target Explorer ) constellation of nanosatellites performs seismology of bright stars via high-precision photometry. In this context, we initiated a high-resolution, high signal-to-noise, high-sensitivity, spectropolarimetric survey of all stars brighter than V = 4. The goal of this survey is to detect new bright magnetic stars and provide prime targets for both detailed magnetic studies and asteroseismology with BRITE . Circularly polarized spectra were acquired with Narval at TBL (Bernard Lyot Telescope, France) and HARPSpol at ESO (European Southern Observatory) in La Silla (Chile). We discovered two new magnetic B stars: the B3V star i Car and the B8V component of the binary star Atlas. Each star was observed twice to confirm the magnetic detections and check for variability. These bright magnetic B stars are prime targets for asteroseismology and for flux-demanding techniques, such as interferometry.

Description: Accreting neutron stars exhibit Type I X-ray bursts from both frequent hydrogen/helium flashes as well as rare carbon flashes. The latter (superbursts) ignite in the ashes of the former. Hydrogen/helium bursts, however, are thought to produce insufficient carbon to power superbursts. Stable burning could create the required carbon, but this was predicted to only occur at much larger accretion rates than where superbursts are observed. We present models of a new steady-state regime of stable hydrogen and helium burning that produces pure carbon ashes. Hot CNO burning of hydrogen heats the neutron star envelope and causes helium to burn before the conditions of a helium flash are reached. This takes place when the mass accretion rate is around 10 per cent of the Eddington limit: close to the rate where most superbursts occur. We find that increased heating at the base of the envelope sustains steady-state burning by steepening the temperature profile, which increases the amount of helium that burns before a runaway can ensue.

Description: We present new late-time near-infrared imaging of the site of the nearby core-collapse supernova SN 2012aw, confirming the disappearance of the point source identified by Fraser et al. and Van Dyk et al. as a candidate progenitor in both J and Ks filters. We remeasure the progenitor photometry, and find that both the J and Ks magnitudes of the source are consistent with those quoted in the literature. We also recover a marginal detection of the progenitor in H -band, for which we measure H = 19.67 ± 0.40 mag. Comparing the luminosity of the progenitor to stellar evolutionary models, SN 2012aw appears to have resulted from the explosion of a 12.5 ± 1.5 M red supergiant.

Description: We derive the carbon monoxide (CO) luminosity function (LF) for different rotational transitions [i.e. (1–0), (3–2), (5–4)] starting from the Herschel LF by Gruppioni et al. and using appropriate L CO – L IR conversions for different galaxy classes. Our predicted LFs fit the data so far available at z 0 and 2. We compare our results with those obtained by semi-analytical models (SAMs): while we find a good agreement over the whole range of luminosities at z 0, at z 1 and z 2, the tension between our LFs and SAMs in the faint and bright ends increases. We finally discuss the contribution of luminous active galactic nucleus ( L X 〉 10 44 erg s – 1 ) to the bright end of the CO LF concluding that they are too rare to reproduce the actual CO LF at z 2.

Description: The formation of the Milky Way stellar halo is thought to be the result of merging and accretion of building blocks such as dwarf galaxies and massive globular clusters. Recently, Deason et al. suggested that the Milky Way outer halo formed mostly from big building blocks, such as dwarf spheroidal galaxies, based on the similar number ratio of blue straggler (BS) stars to blue horizontal branch (BHB) stars. Here we demonstrate, however, that this result is seriously biased by not taking into detailed consideration on the formation mechanism of BHB stars from helium-enhanced second-generation population. In particular, the high BS-to-BHB ratio observed in the outer halo fields is most likely due to a small number of BHB stars provided by globular clusters (GCs) rather than to a large number of BS stars. This is supported by our dynamical evolution model of GCs which shows preferential removal of first-generation stars in GCs. Moreover, there are a sufficient number of outer halo GCs which show very high BS-to-BHB ratio. Therefore, the BS-to-BHB number ratio is not a good indicator to use in arguing that more massive dwarf galaxies are the main building blocks of the Milky Way outer halo. Several lines of evidence still suggest that GCs can contribute a significant fraction of the outer halo stars.

Description: Nuclear star clusters (NCs) are found to exist in the centres of many galaxies and appear to follow scaling relations similar to those of supermassive black holes. Previous analytical work has suggested that such relations are a consequence of feedback-regulated growth. We explore this idea using high-resolution hydrodynamical simulations, focusing on the validity of the simplifying assumptions made in analytical models. In particular, we investigate feedback emanating from multiple stellar sources rather than from a single source, as is usually assumed, and show that collisions between shells of gas swept up by feedback leads to momentum cancellation and the formation of high-density clumps and filaments. This high-density material is resistant both to expulsion from the galaxy potential and to disruption by feedback; if it falls back on to the NC, we expect the gas to be available for further star formation or for feeding a central black hole. We also note that our results may have implications for the evolution of globular clusters and stellar clusters in high-redshift dark matter haloes.

Description: We explain the axisymmetric gaps seen in recent long-baseline observations of the HL Tau protoplanetary disc with the Atacama Large Millimetre/Submillimetre Array (ALMA) as being due to the different response of gas and dust to embedded planets in protoplanetary discs. We perform global, three-dimensional dusty smoothed particle hydrodynamics calculations of multiple planets embedded in dust/gas discs which successfully reproduce most of the structures seen in the ALMA image. We find a best match to the observations using three embedded planets with masses of 0.2, 0.27 and 0.55 M J in the three main gaps observed by ALMA, though there remain uncertainties in the exact planet masses from the disc model.

Description: Using deep Herschel and ALMA observations, we investigate the star formation rate (SFR) distributions of X-ray-selected active galactic nucleus (AGN) host galaxies at 0.5 〈  z  〈 1.5 and 1.5 〈  z  〈 4, comparing them to that of normal, star-forming (i.e. ‘main-sequence’, or MS) galaxies. We find that 34–55 per cent of AGNs in our sample have SFRs at least a factor of 2 below that of the average MS galaxy, compared to 15 per cent of all MS galaxies, suggesting significantly different SFR distributions. Indeed, when both are modelled as lognormal distributions, the mass and redshift-normalized SFR distributions of X-ray AGNs are roughly twice as broad, and peak 0.4 dex lower, than that of MS galaxies. However, like MS galaxies, the normalized SFR distribution of AGNs in our sample appears not to evolve with redshift. Despite X-ray AGNs and MS galaxies having different SFR distributions, the linear-mean SFR of AGNs derived from our distributions is remarkably consistent with that of MS galaxies, and thus with previous results derived from stacked Herschel data. This apparent contradiction is due to the linear-mean SFR being biased by bright outliers, and thus does not necessarily represent a true characterization of the typical SFR of X-ray AGNs.

Description: We investigate the density–shear instability in Hall-magnetohydrodynamics (Hall-MHD) via numerical simulation of the full non-linear problem in the context of magnetar activity. We confirm the development of the instability of a plane-parallel magnetic field with an appropriate intensity and electron density profile, in accordance with analytic theory. We find that the instability also appears for a monotonically decreasing electron number density and magnetic field, a plane-parallel analogue of an azimuthal or meridional magnetic field in the crust of a magnetar. The growth rate of the instability depends on the Hall properties of the field (magnetic field intensity, electron number density and the corresponding scaleheights), while being insensitive to weak resistivity. Since the Hall effect is the driving process for the evolution of the crustal magnetic field of magnetars, we argue that this instability is critical for systems containing strong meridional or azimuthal fields. We find that this process mediates the formation of localized structures with much stronger magnetic field than the average, which can lead to magnetar activity and accelerate the dissipation of the field and consequently the production of Ohmic heating. Assuming a 5  x  10 14  G magnetic field at the base of crust, we anticipate that magnetic field as strong as 10 15  G will easily develop in regions of typical size of a few hundred metres, containing magnetic energy of 10 43  erg, sufficient to power magnetar bursts. These active regions are more likely to appear in the magnetic equator where the tangential magnetic field is stronger.

Description: A model combining qualitative and historical quantitative data in an innovative rule-based fuzzy cognitive map framework is used to assess and compare the long-term bioeconomic impact of adopting gear modifications aimed at reducing bycatch in the Portuguese crustacean trawl fishery. The impact of codend-related changes (mesh size and shape) and the introduction of a sorting device (sorting grid system) on the main target crustacean species (deepwater rose shrimp Parapenaeus longirostris and Norway lobster Nephrops norvegicus ) and the main fish bycatch species (blue whiting Micromesistius poutassou , horse mackerel Trachurus trachurus , and European hake Merluccius merluccius ) were evaluated. Horse mackerel was the only fish species for which changing codends negatively affected landings per unit of effort by large percentages. The use of a sorting grid system, only evaluated for blue whiting and Norway lobster, led to a strong decrease in landings per unit of effort, especially for the former species. The impact of gear alterations was negligible on fish spawning-stock biomass, but was significant for crustaceans, particularly rose shrimp. A straightforward evaluation of the economic impact (fishers' revenues) of the three bycatch reduction options showed these to be negligible or small.

Description: The difficulty of ensuring adequate statistical coverage of whole fleets is a challenge for the implementation of observer programmes and may reduce the usefulness of the data they obtain for management purposes. This makes it necessary to find cost-effective alternatives. Electronic monitoring (EM) systems are being used in some fisheries as an alternative or a complement to human observers. The objective of this study was to test the use and reliability of EM on the tropical tuna purse-seine fishery. To achieve this objective, seven trips of tuna purse seiners operating in the three Oceans were closely monitored to compare the information provided by EM and on-board observers to determine if EM can reliably document fishing effort, set type, tuna catch, and bycatch. Total tuna catch per set was not significantly different between EM and observer datasets; however, regarding species composition, only main species matched between EM and observers. Success on set-type identification using EM varied between 98.3 and 56.3%, depending on the camera placement. Overall, bycatch species were underestimated by EM, but large bodied species, such as billfishes, were well documented. The analyses in this study showed that EM can be used to determine the fishing effort (number of sets) and total tuna catch as reliably as observers can. Set-type identification also had very promising results, but indicated that refinement of the methods is still needed. To be fully comparable with observer data, improvements for accurately estimating the bycatch will need to be developed in the application and use of the EM system. Operational aspects that need to be improved for an EM programme to be implemented include standardizing installation and on-board catch handling methodology as well as improvements in video technology deployment.

Description: In this paper, we synthesize information presented at the 2nd Fishery Dependent Information (FDI) Conference, held in Rome, Italy, from 2 to 6 March 2014. We review current issues and advances in the collection, interpretation and application of fishery-dependent data, and highlight emergent findings in the field. Key issues include (i) the design and collection of data associated with commercial and recreational fisheries and the use of these data to support conventional and novel approaches to fisheries science and management and (ii) the role of fishers in co-management and policy setting. We noted that since the 2010 FDI conference a paradigm shift towards full engagement of key stakeholders started to take place. It also became evident that trust between stakeholders, managers, and scientists is necessary to develop efficient fishery monitoring programmes. While building such trust among key players often begins in informal settings, eventually one must evolve structured, formalized, and agreed processes for such interactions. We also conclude that because of the diversity of fisheries any determination of "best practices" may be difficult. Instead, we provide a list of "best principles" emerged from the conference.

Description: The walleye pollock ( Gadus chalcogrammus ) fishery in the Bering Sea is one of the largest fisheries in the world. The North Pacific Fishery Management Council (NPFMC) provides management advice for this fishery, including the development of measures to minimize salmon bycatch to the extent practicable, one of the stated objectives of the US Magnuson–Stevens Fishery Conservation and Management Act National Standard Guidelines. Salmon have a unique cultural and nutritional importance in the State of Alaska and are the subject of fully allocated mixed commercial, recreational, and subsistence fisheries. Chinook salmon ( Oncorhynchus tshawytscha ) stocks in Alaska have been declining for the last decade, and all sources of mortality are being considered to help in rebuilding stocks. Given the extensive scientific National Marine Fisheries Service observer data collection programme, the NPFMC has developed bycatch management measures that place limits by fishery sector on the allowable catch of Chinook salmon. Part of this programme includes industry-proposed incentive programmes designed to encourage lower bycatch. Evaluating the efficacy of the new measures poses a number of challenges, particularly in light of changing ocean conditions (perhaps affecting the degree of overlap between pollock and salmon). In this study, data on pre- and post-programme implementation were evaluated to determine if the programme is meeting stated goals and objectives or if modifications are needed. These evaluations included consideration of fleet-level bycatch numbers and rates, seasonality of bycatch by sector, and individual vessel bycatch rates. Results suggest that revised management regulations appear to have resulted in reduced bycatch of salmon overall. Also, lower bycatch rates seem to reflect changing behaviour in response to new management measures. However, the extent to which the programme is effective at the vessel level remains difficult to ascertain without explicit vessel-specific benchmarks developed for evaluating programme efficacy.

Description: Part of the European Union (EU) Common Fisheries Policy revision of 2013 is a commitment to implement a land-all policy, under which the practice of discarding caught fish back into the sea will be forbidden. This measure will be applied first to the pelagic fleet in 2015, with a phased implementation for the demersal fleet between 2016 and 2019. As part of trials to determine the efficacy of a land-all policy for North Sea cod ( Gadus morhua L.), Remote Electronic Monitoring (REM) systems were installed on seven Scottish demersal vessels in 2008. Vessels were permitted additional days-at-sea and cod quota, and were obliged to land all cod caught in the North Sea. This arrangement has been renewed each year as part of the Scottish Cod Conservation Credits scheme, and while the list of vessels involved has not remained constant, the scheme remains attractive to skippers (27 vessels in 2014), has always been oversubscribed, and is likely to remain a key part of the Scottish Government's approach to land-all enforcement. Marine Scotland Science is granted access to all REM data collected from Scottish vessels. This paper summarizes the scientific analyses carried out using these data from 2008 onwards, including the installation and operation of REM systems for scientific purposes; the programme developed to train REM analysts; systems for combining length measurements with fish counts; the potential use of REM data in management advice; and studies on such aspects as discard-rate estimation, activity mapping, estimating the relative costs of on-board and REM observation, morphometric length inference, and automated image analysis. We conclude that, while further development work is certainly needed, REM provides a rich source of fisheries information for science as well as for compliance and management. However, care will need to be taken to ensure that science monitoring and analysis resources do not become overwhelmed.

Description: Chinook salmon ( Oncorhynchus tshawytscha ) are taken as bycatch in the Bering Sea pollock ( Gadus chalcogrammus ) fishery, with recently revised management measures in place to limit the overall Chinook salmon catch. Historical impact of the bycatch on regional salmon stocks is made difficult because, until recently, sampling for the stock composition of the bycatch was patchy and diverse in approaches. In this study, extensive observer data on the biological attributes (size and age composition) of the bycatch were used to estimate the impact on specific regional stock groups (RSGs), as defined given available genetic stock identification estimates. Our model provides estimates of the impact on Chinook salmon RSGs, given seasonal and spatial variability in the bycatch, and accounts for observed in-river age compositions, uncertainty in age-specific oceanic natural mortality of Chinook salmon, and between-year variability in genetic information. The upper Yukon River stock is transboundary and subject to heightened management interest and international management agreements on escapement goals. Our study updates results from an earlier analysis used to develop the management regulations that went into place in 2011. It shows that the new data result in slight changes in previous estimates, and that the lower overall Chinook salmon bycatch since 2008 has resulted in lower impacts to the main western Alaskan RSGs.

Description: Change is an important feature of commercial fisheries; yet the fishing industry, including fishers, fishery management authorities, and other stakeholders, is, in many respects, highly resistant to change. Examples of this include the application of conservation engineering solutions to bycatch problems and transitions towards ecosystem-based fishery management. A key reason for this resistance may be conditioning, cultural conservatism, and uncertainty. Change is often considered uncontrollable and unpredictable and a threat to established processes and systems that forces individuals to face an unknown future. In the business world, many models of change management have been applied to assist individuals and corporations in responding to an ever-changing environment. While fragments of these models have been applied in a fisheries context, the deliberate application of entire models has not. The application of these models could help to improve many aspects of fishery-dependent data collection such as using fishery-dependent information in stock assessment, implementing technologies such as vessel monitoring systems and electronic logbooks, and sharing information that is traditionally not shared. We present a well-known model for change management and describe how its application in a fisheries context can guide change initiatives and produce enhanced outcomes. We also explore how competing commitments and big assumptions influence a fisher's resistance to change, including conservation engineering initiatives, and posit how this can influence their involvement in the collection of fishery-dependent data.

Description: Long expected transition states between the rotation powered and accretion powered non-thermal emission in the millisecond pulsar binary systems have been recently observed in the case of three objects PSR J1023+0038, PSR J1824–2452, and PSR J1227–4859. Surprisingly, the transition is related to the significant change in the -ray flux being a factor of a few higher with the presence of an accretion disc. The origin of this enhanced emission seems to be related to the penetration of the inner pulsar magnetosphere by the accretion disc. We propose that the radiation processes, characteristic for the rotation powered pulsar, can co-exist with the presence of an accretion disc in the inner pulsar magnetosphere. In our scenario additional -ray emission is produced by secondary leptons, originated close to the acceleration gap, which Compton up-scatter thermal radiation from the accretion disc to GeV energies. The accretion disc penetrates deep into the pulsar magnetosphere allowing the matter to fall on to the neutron star surface producing pulsed X-ray emission. We show that the sum of the rotation powered pulsar -ray emission, produced by the primary electrons in the curvature process, and the -ray emission, produced by secondary leptons, can explain the observed high-energy radiation from the redback binary pulsar PSR J1227–4853 in the state with evidences of the accretion disc.

Description: A new thermodynamic model is presented for calculating phase relations in peridotite, from 0·001 to 60 kbar and from 800°C to liquidus temperatures, in the system NCFMASOCr. This model system is large enough to simulate phase relations and melting of natural peridotite and basaltic liquids. Calculations in the program thermocalc illustrate mantle phase relationships and melting conditions, specifically for the peridotite composition KLB-1. The garnet–spinel transition zone intersects the solidus at 21·4–21·7 kbar, where both Fe 3+ and Cr increase spinel stability, expanding the width of the transition. Orthopyroxene is lost at the solidus at 42 kbar in KLB-1, although this pressure is very sensitive to bulk composition. Calculated oxidation states are in excellent agreement with measured log f O 2 for xenolith suites with mantle Fe 2 O 3 contents in the range 0·1–0·3 wt %. It appears that mantle oxidation state is not just a simple function of P and T , but depends on phase assemblage, and may vary in a complex way within a single assemblage. The liquid model performs well, such that calculated solidus, melt productivity and liquid compositions compare favourably with those of experimental studies, permitting its use in interpolating between, and extrapolating from, experimental P–T conditions. Experimentally challenging but geologically useful regimes can be explored, such as subsolidus samples and very low melt fractions, with application to both mantle xenoliths and the origin of basalt.

Description: The anorthositic members of the Mealy Mountains Intrusive Suite (MMIS; Labrador, Canada) are host to 0·5–5 m diameter pegmatitic, pod-like segregations, originally described as graphic granite pods. U–Pb zircon geochronology confirms that the pods are coeval with the 1650–1630 Ma emplacement age range for the MMIS, yielding ages of 1654 ± 8 to 1628 ± 3·5 Ma. Petrographic and geochemical analysis of five pods from anorthositic rocks of the MMIS reveals that the pods have a diverse compositional range from monzodiorite to granite, varying from Fe-rich and Si-poor, to Fe-poor and Si-rich compositions. Fe-rich, Si-poor pods in the MMIS and other massifs (e.g. Laramie Anorthosite Complex) tend to be hosted by olivine-bearing anorthosites, whereas Si-rich, Fe-poor pods are hosted by pyroxene-bearing anorthosites. Each pod shows a range of graphic, myrmekitic and symplectitic textures, along with distinctive mineral assemblages (e.g. apatite and zircon) and highly enriched trace-element compositions. Evolved mineral assemblages, high concentrations of Fe, Ti and P (and in some cases SiO 2 ), and 10–1000 x chondrite enrichment in light rare earth elements, U, Th and Rb indicate that many of the pods are highly fractionated. The array of textural intergrowths provides clues about the final stages of crystallization in the pods and, by extension, the anorthosites. Macroscopic quartz–K-feldspar graphic intergrowths indicate high-viscosity, fluid-bearing and significantly undercooled magmatic conditions, whereas microscopic myrmekitic (plagioclase–quartz) and symplectitic (plagioclase–orthopyroxene) intergrowths on primary grain boundaries indicate replacement of phases in the presence of reactive fluids. In assessing the nature of these pegmatitic pods based on field, petrographic and geochemical evidence, we conclude that they represent the fluid-bearing, late-stage crystallization products of a residual liquid in the massif anorthosite system. The Fe and Si compositional variations observed in these late-stage pods can be linked to a fundamental olivine–pyroxene dichotomy observed in most Proterozoic anorthosite massifs, suggesting that pulses of magma experience variable contamination (in amount and/or composition) leading to varying differentiation paths. A range of lithologies (monzonites, monzonorites, ferrodiorites and jotunites) observed in similar pod-like structures, as well as dykes and plutons, has been observed in other Proterozoic anorthosite massifs and all have, at one time or another, been interpreted as the residual liquids of anorthosite crystallization. Our observation of in situ pods with similar compositions to all of the aforementioned lithologies, and displaying textures indicative of late-stage crystallization, supports the notion that all of these associated lithologies can be interpreted as comagmatic with, but variably contaminated and isolated residual liquids of, anorthosite crystallization. However, using isotopic evidence we cannot support the notion that the far larger granitic plutons associated with Proterozoic anorthosites are also residual liquids of anorthositic magma fractionation.

Description: We report the results of experiments on two natural marine sediments with different carbonate contents (calcareous clay: CO 2 = 6·1 wt %; marl: CO 2 = 16·2 wt %) at subduction-zone conditions (3 GPa, 750–1200°C). Water (7–15 wt %) was added to the starting materials to simulate the effects of external water addition from within the subducting slab. The onset of melting is at 760°C in water-rich experiments; melt becomes abundant by 800°C. In contrast, the onset of melting in published, water-poor experiments occurs at variable temperatures with the production of significant melt fractions being restricted to more than 900°C (phengite-out). The different solidus temperatures ( T solidus ) can be ascribed to variable fluid X H2O [H 2 O/(CO 2 + H 2 O)], which, in turn, depends on bulk K 2 O, H 2 O and CO 2 . Partial melts in equilibrium with residual garnet, carbonate, quartz/coesite, epidote, rutile, kyanite, phengite, and clinopyroxene are granitic in composition, with substantial dissolved volatiles. Supersolidus runs always contain both silicate melt and solute-rich fluid, indicating that experimental conditions lie below the second critical endpoint in the granite–H 2 O–CO 2 system. Carbonatite melt coexists with silicate melt and solute-rich fluid above 1100°C in the marl. The persistence of carbonate to high temperature, in equilibrium with CO 2 -rich hydrous melts, provides a mechanism to both supply CO 2 to arc magmas and recycle carbon into the deep Earth. The trace element compositions of the experimental glasses constrain the potential contribution of calcareous sediment to arc magmas. The presence of residual epidote and carbonate confers different trace element characteristics when compared with the trace element signal of Ca-poor marine sediments (e.g. pelagic clays). Notably, epidote retains Th and light rare earth elements, such that some melts derived from calcareous sediments have elevated Ba/Th and U/Th, and low La/Sm PUM , thereby resembling fluids conventionally ascribed to altered oceanic crust. Our results emphasize the importance of residual mineralogy, rather than source lithology, in controlling the trace element characteristics of slab-derived fluids.

Description: Three crystal-poor obsidian samples (one dacite, 67 wt % SiO 2 ; two rhyolites, 73 and 75 wt % SiO 2 ), which erupted effusively from monogenetic vents, contain sparse (〈2%) plagioclase phenocrysts that span a remarkably wide and continuous range in composition (≤30 mol % An). Many, but not all, of the plagioclase crystals display diffusion-limited growth textures (e.g. swallow-tails, skeletal, vermiform). Hypotheses to explain the paradox of a wide compositional range despite a low abundance of plagioclase include (1) incorporation of xenocrysts and/or magma mingling, (2) slow crystallization of plagioclase driven by slow cooling in a magma chamber, (3) slow crystallization of plagioclase followed by a resorption (e.g. heating) event, and (4) crystallization driven by rapid degassing (i.e. loss of melt H 2 O) ± rapid cooling during ascent. To test these hypotheses, a series of phase equilibrium experiments were conducted under pure-H 2 O fluid-saturated conditions in a cold-seal pressure vessel between 30 and 300 MPa and 750 and 950°C. The results show that the plagioclase population in each obsidian sample could have grown from their respective melts, with the exception of a single calcic core (An 60–63 ) in one sample. The results additionally rule out slow cooling in a magma chamber, because this would lead to equilibrium abundances of plagioclase (≤20%), which are far higher than what is observed in the samples (〈2%). Nor can resorption (i.e. heating) explain the low abundance of plagioclase, because this would eliminate the more sodic plagioclase crystals and hence the wide compositional range of plagioclase that is observed. The most viable hypothesis is that the sparse plagioclase phenocrysts grew relatively rapidly during magma ascent to the surface; this is consistent with the results of isothermal (850°C) continuous decompression experiments (2·9, 1·0, 0·8, and 0·1 MPa h –1 ), under pure-H 2 O fluid-saturated conditions, which were performed on one of the rhyolites (MLV-36; 73 wt % SiO 2 ) and quenched at P H2O = 89, 58 and 40 MPa. The four decompression rates correspond to degassing rates of 1·6, 0·56, 0·45 and 0·06 wt % H 2 O per day. Decompressions ≥1·0 MPa( P H2O ) h –1 , initiated above the liquidus, quenched to 100% glass at all final P H2O . Decompressions at 0·8 MPa( P H2O ) h –1 , also initiated above the liquidus, led to plagioclase crystals nearly five times larger than those grown in runs decompressed at the same rate, but initiated just below the plagioclase-in curve. It is the kinetic hindrance to nucleation that permits crystal growth to be concentrated on relatively few crystals, leading to larger crystals. Plagioclase growth rates from these experiments show that the largest phenocrysts (~1 mm) in the MLV-36 obsidian could have grown in 〈42 h. A cooling rate of ~1·2°C h –1 closely matches both the increase in melt viscosity with time and the effective undercooling with time that occurs during the 0·8 MPa( P H2O ) h –1 decompression over the first 50 h. The combined results point to crystallization of sparse plagioclase driven by relatively rapid rates of degassing ± cooling during ascent to the surface of melts that were initially above their liquidus. The obsidian samples must have been efficiently segregated as nearly 100% liquids from their respective source regions at H 2 O-fluid undersaturated conditions to attain a degree of superheating upon ascent before reaching fluid saturation.

Description: The Jurassic Vestfjella dyke swarm at the volcanic rifted margin of western Dronning Maud Land represents magmatism related to the incipient Africa–Antarctica rift zone; that is, rift-assemblage magmatism of the Karoo continental flood basalt (CFB) province. Geochemical and Nd–Sr isotopic data for basaltic and picritic dyke samples indicate diverse low-Ti and high-Ti tholeiitic compositions with Nd (180 Ma) ranging from +8 to –17. Combined with previously reported data on a subcategory of ferropicritic dykes, our new data facilitate grouping of the Vestfjella dyke swarm into seven geochemically distinct types. The majority of the dykes exhibit geochemical affinity to continental lithosphere and can be correlated with two previously identified chemical types (CT) of the wall-rock CFB lavas and are accordingly referred to as the CT1 and CT3 dykes. The less abundant Low-Nb and High-Nb dykes, a relatively enriched subtype of CT3 (CT3-E) dykes, and dykes belonging to the depleted and enriched ferropicrite suites represent magma types found only as intrusions. The chemically mid-ocean ridge basalt (MORB)-like Low-Nb and the depleted ferropicrite suite dykes represent, respectively, relatively high- and low-degree partial melting of the same overall depleted mantle (DM)-affinity source in the sublithospheric mantle. In contrast, we ascribe the chemically ocean island basalt (OIB)-like High-Nb dykes and the enriched ferropicrite suite dykes to melting of enriched components in the sublithospheric mantle. Geochemical modelling suggests that the low-Ti affinity CT1 and CT3, and high-Ti affinity CT3-E magma types of Vestfjella dyke may predominantly result from mixing of DM-sourced Low-Nb type magmas with 〈10 wt % of crust- and lithospheric mantle-derived melts. U/Pb zircon dating confirms synchronous emplacement of CT1 dykes and Karoo main-stage CFBs at 182·2 ± 0·9 and 182·2 ± 0·8 Ma, whereas two 40 Ar/ 39 Ar plagioclase plateau ages of 189·2 ± 2·3 Ma (CT1) and 185·5 ± 1·8 Ma (depleted ferropicrite suite), and a mini-plateau age of 186·9 ± 2·8 Ma (CT3-E) for the Vestfjella dykes raise the question of whether the onset of rift-zone magmatism could predate the province-wide c. 179–183 Ma main stage of Karoo magmatism. Notably variable Ca/K spectra suggest that younger 40 Ar/ 39 Ar plagioclase plateau ages of 173, 170, 164, and 154 Ma are related to crystallization of secondary minerals during the late-stage tectono-magmatic development of the Antarctic rifted margin. The occurrence of rare MORB- and OIB-like magma types in Vestfjella and along the African and Antarctic rifted margins suggests melting of geochemically variable depleted and enriched sublithospheric mantle beneath the Africa–Antarctica rift zone. Our models for the Vestfjella dyke swarm indicate that the voluminous lithosphere-affinity low-Ti and high-Ti rift-assemblage tholeiites could have been derived from MORB-like parental magmas by contamination, which implies sublithospheric depleted mantle as the principal source of the CFB magmas of the Africa–Antarctica rift zone.

Description: Monazite laser ablation–split-stream inductively coupled plasma–mass spectrometry (LASS) was used to date monazite in situ in Barrovian-type micaschists of the Moravian zone in the Thaya window, Bohemian Massif. Petrography and garnet zoning combined with pseudosection modelling show that rocks from staurolite–chlorite, staurolite, kyanite and kyanite–sillimanite zones record burial in the S 1 fabric under a moderate geothermal gradient from 4–4·5 kbar and ~530–540°C to 5 kbar and 570°C, 6–7 kbar and 600–640°C, 7·5–8 kbar and 630–650°C, and 8 kbar and 650°C, respectively. In the kyanite and kyanite–sillimanite zones, garnet rim chemistry and local syntectonic replacement of garnet by sillimanite–biotite aggregates point to re-equilibration at 5·5–6 kbar and 630–650°C in the S 2 fabric. Heterogeneously developed retrograde shear zones (S 3 ) are marked by widespread chloritization, but minor chlorite is present in the studied samples. Monazite abundance and size increase with metamorphic grade from 5 µm in the staurolite–chlorite zone to 〉100 µm in the kyanite and kyanite–sillimanite zones. Irrespective of the monazite-forming reaction, this is interpreted as the onset of limited prograde monazite growth at staurolite grade, and continued prograde monazite growth after the kyanite-in reaction, compatible with conditions of about 5·5 kbar and 570°C and 7·5 kbar and 630°C from pseudosection modelling. Monazite is zoned, showing embayments and sharp boundaries between zones, with low Y in the staurolite zone, high-Y cores and low-Y rims in the kyanite zone, and high-Y cores, a low-Y mantle and a high-Y rim in the sillimanite zone. The 207 Pb-corrected 238 U/ 206 Pb ages from three samples range from 344 ± 7 to 330 ± 7 Ma, irrespective of metamorphic grade. The dates from monazite inclusions are interpreted as the ages of the staurolite- and kyanite-in reactions along the prograde path at 340 and 337 ± 7 Ma, respectively. The monazite in the matrix (and some inclusions) is interpreted as dating the prograde crystallization at (340–337) ± 7 Ma within the S 1 fabric, and then being affected by recrystallization at or down to 332 ± 7 Ma in the S 2 and S 3 fabrics. The two groups of data, for 340–337 and 332 Ma, are significantly different when only their in-run uncertainties (±1–3 Myr) are compared and indicate a 9 ± 3 Myr period of monazite (re)crystallization. A systematic increase in heavy rare earth element (HREE) content with decreasing monazite age from 344 to 335 Ma is correlated with growth on the prograde P–T path; the drop in HREE of monazite at 335–328 Ma is assigned to recrystallization. The presence of chlorite even in the least retrogressed samples witnesses limited external fluid availability on the retrograde P–T path. Migration of this fluid was probably responsible for heterogeneous fluid-assisted recrystallization and resetting of original prograde monazite, even where included in garnet, staurolite or kyanite. It is suggested that the rocks passed the chlorite-in reaction on the retrograde path at 332 ± 7 Ma. The timing of burial in the Thaya window, a deformed part of the underthrust Brunia microcontinent, was coeval with exhumation of granulites and migmatites of the Moldanubian orogenic root at c. 340 Ma.

Description: The Fanshan intrusion in the North China Craton (NCC) is concentrically zoned with syenite in the core (Unit 1), surrounded by ultramafic rocks (clinopyroxenite and biotite clinopyroxenite; Unit 2), and an outer rim of garnet-rich clinopyroxenite and orthoclase clinopyroxenite and syenite (Unit 3). The intrusive rocks are composed of variable amounts of Ca-rich augite, biotite, orthoclase, melanite, garnet, magnetite and apatite, with minor primary calcite. Monomineralic apatite rocks, nelsonite and glimmerite exclusively occur in Unit 2. Geochemically, the Fanshan rocks are highly enriched in light rare earth elements (LREE) and large ion lithophile elements (LILE), moderately depleted in high field strength elements (HFSE), and have a limited range of Sr–Nd–O isotopic compositions. The similar mineralogy, mineral compositions, and trace element characteristics of the three units suggest that all the rocks are co-magmatic. The parental magma is ultrapotassic and is akin to kamafugite. Very low-degree partial melting of metasomatized lithospheric mantle best explains the geochemistry and petrogenesis of the parental magmas of the Fanshan intrusion. We propose that the mantle source may have been metasomatized by a hydrous carbonate-bearing melt, which has imprinted the enriched Sr–Nd isotopic signature and incompatible element enrichment with conspicuous negative Nb–Ta–Zr–Hf–Ti anomalies and LREE enrichments. The mantle source enrichment may be correlated with oceanic sediment recycling during southward subduction of the Paleo-Asian oceanic plate during the Carboniferous and Permian. We propose that crystal settling and mechanical sorting combined with repeated primitive magma replenishment and mixing with previously fractionated magma is the predominant process responsible for the formation of the apatite ores.

Description: During the last centuries, populations of marine megafauna—such as seabirds, turtles, and mammals—were intensively exploited. At present, other threats such as bycatch and pollution affect these species, which play key ecological roles in marine ecosystems as apex consumers and/or nutrient transporters. This study analyses the distribution of six megafaunal species ( Chelonia mydas , Caretta caretta , Dermochelys coriacea , Thalassarche melanophris , Otaria flavescens , and Arctocephalus australis ) coexisting in the Southwestern Atlantic to discuss their protection in terms of current management strategies in the region. Through the prediction of the species potential distributions and their relation to bathymetry, sea temperature and oceanographic fronts, key ecological areas are defined from a multi-taxa perspective. Information on the distribution of 70 individuals (18 sea turtles, 19 albatrosses, and 33 otariids) was obtained through satellite tracking conducted during 2007–2013 and analysed using a Geographic Information System and maximum entropy models. During the autumn–winter period, megafaunal species were distributed over the continental shelves of Argentina, Uruguay, and Brazil, mainly over the Argentine Exclusive Economic Zone and the Argentina-Uruguay Common Fishing Zone. Despite some differences, all megafaunal species seems to have similar environmental requirements during the autumn–winter period. Mostly waters shallower than 50 m were identified as key ecological areas, with the Río de la Plata as the habitat with the highest suitability for all the species. This area is highly productive and sustains the main coastal fisheries of Uruguay and Argentina, yet its role as a key ecological area for megafaunal species has been underestimated until now. This approach provides a basis to analyse the effect of anthropic activities on megafaunal species through risk maps and, ultimately, to generate knowledge to improve national and bi-national management plans between Argentina and Uruguay.

Description: In the North Sea flatfish fishery, electric pulse trawls have been introduced to replace the conventional mechanical method. Pulse trawls reduce the fuel consumption, reduce adverse impact on the ecosystem but cause injuries in gadoids. We describe the design and electrical properties of pulse trawls currently in use and study the behavioural response and injuries in cod exposed to electrical pulses under controlled conditions. Pulse trawls operate at an average power of 0.7 kW m –1 beam length and a duty cycle of ~2%. The electric field is heterogeneous with highest field strength occurring close to the conductors. Cod were exposed to three different pulse types for a range of field strengths, frequencies, and duty cycles. Two size classes were tested representing cod that escape through the meshes (11–17 cm) and market-sized cod that are retained in the net (34–56 cm). Cod exposed to a field strength of ≥37 V m –1 responded by moderate-to-strong muscular contractions. Some of the large cod ( n = 260) developed haemorrhages and fractures in the spine, and haemal and neural arches in the tail part of the body. The probability of injuries increased with field strength and decreased when frequency was increased from 100 to 180 Hz. None of the small cod ( n = 132) were injured and all survived. The field strength at the lateral boundaries of the trawl was too low to inflict injuries in cod.

Description: A coupled biophysical model is used to explore the physical controls involved in the timing of the spring phytoplankton bloom in fjords. Observations from Rivers Inlet, British Columbia, are used to force and evaluate the model. It is found that the interannual variation in timing is due primarily to variations in retention, in particular, to variations in horizontal advection out of the fjord. The two dominant processes are (i) strong outflow winds rapidly advecting the surface layer and thus the phytoplankton population out of the fjord and (ii) losses due to high river flux increasing the estuarine circulation. Both processes delay the timing of spring bloom. Smaller effects on the interannual variation are due to increased wind mixing which deepens the mixing layer and reduces light to phytoplankton, and increased river flow which increases the stratification and decreases the mixing layer depth. Observed interannual variations in cloudiness were small. Strong outflow winds are common in winter along the British Columbia coast, but generally cease after the spring wind transition. Thus, observed interdecadal variations in the spring transition date probably imply strong variations in the timing of spring phytoplankton blooms in British Columbia fjords.

Description: Since "balanced harvest" was proposed in 2010 as a possible tool in the operationalization of the ecosystem approach to fisheries (EAF), the concept gained extensive international attention. Because maintaining ecosystem structure and achieving maximum sustainable yields have become two of the key international legal obligations in fisheries management, balanced harvest is as topical as ever. An international workshop on balanced harvest, organized by the IUCN Fisheries Expert Group at FAO headquarters in 2014, reviewed the progress in the field and discussed its prospects and challenges. Several articles in this theme set, mostly based on presentations from the workshop, discuss ecological, economical, legal, social, and operational issues surrounding the key management goals. Progress is being made on understanding of the theoretical underpinnings of balanced harvest and its practical feasibility. Yet, a basic debate on the concept of balanced harvest continues. To move the EAF forward, we anticipate and encourage further research and discussion on balanced harvest and similar ideas.

Description: Sampling of euphausiids is difficult because of their intermediate size between macrozooplankton and micronekton. The Barents Sea is one of the few marine areas where there have been long-term studies of euphausiids. We have examined three monitoring datasets on euphausiids and consider likely sources of errors associated with the sampling. Results indicated a high degree of patchiness in the distribution of euphausiids, even at the largest scale of sampling with a pelagic trawl. This indicates that euphausiids may occur in large, but infrequent, swarms that have a low probability of being sampled by small nets. The mean biomass of euphausiids sampled with MOCNESS was 2 g wet weight m –2 integrated over the water column, which is an underestimate due to avoidance of large individuals. The mean biomass obtained with pelagic trawl in the upper 60 m of water at night during an autumn survey was 10 g wet weight m –2 . The plankton net on bottom trawl collected mean and median density of euphausiids (0.1–0.2 g wet weight m –3 ) near bottom during a winter survey similar to the values found with pelagic trawl in the upper layer during autumn. The mean density for the autumn survey showed an increase from 2000 to 2011, while the winter survey showed generally a decrease from 2000–2007 to 2011. The increase in the autumn series coincided with a general warming trend presumably with a larger influx of euphausiids with Atlantic water, notably of Meganyctiphanes norvegica . In contrast, the decline during winter may reflect a decrease, particularly of Thysanoessa raschii in the southeastern Barents Sea in the most recent years. Improvements in sampling gears combined with more and better use of acoustical and optical technologies offer great promise for improved monitoring and quantification of the roles of euphausiids in the Barents Sea ecosystem.

Description: Balanced fishing proposes a considerable change to current fisheries management to increase overall biomass harvested while reducing the ecosystem impacts of large-scale fisheries. However, to date, the work to a large degree has focused on simplified models, which exclude much of the variability in real ecosystems, as well as basing harvesting rates on a perfect, but unrealistic, knowledge on stock productivity. Furthermore, the published studies have avoided examining the practicalities of implementing balanced fishing in a real world. This has resulted in a gap that remains to be overcome before balanced fishing can be considered a viable management strategy for large marine ecosystems. We discuss variability in recruitment, in biology and life history characteristics, in data quality, and in fishing practice and management, and their implications for implementation of balanced fishing, using examples from the Barents Sea. We try to outline the complexities that need to be investigated as a precursor to moving balanced fishing from an academic exercise to a practical management scheme. Given the difficulties in moving to "full" balanced fishing, we highlight the importance of investigating to what extent benefits can be gained by implementing only the most achievable parts of a balanced fishing regime.

Description: European eel ( Anguilla anguilla ) is considered as critical endangered and even under the best circumstances it may take decades before the stock recovers. Estimation of eel escapement biomass, B escapement , is of critical importance to evaluate management schemes and to predict the recovery potential for the eel stock. Westerberg and Wickström (2015. Stock assessment of eels in the Baltic: reconciling survey estimates to achieve quantitative analysis. ICES Journal of Marine Science, 73: 75–83) attempt to estimate potential B escapement based on the assumptions that all elvers at the entrance of the Baltic also migrate into the Baltic Sea and that natural mortality is low under the whole growth stage (close to 0.02 at the age of 10 years and older). As a consequence, Westerberg and Wickström estimated the present potential B escapement at ~10–20 000 tonnes and fishing mortality close to 0.05–0.10, while it was also suggested that other sources of anthropogenic mortality may reduce the actual escapement to unknown levels. Here we argue that these conclusions are entirely speculative and contradicted by tagging experiment and fishery data, which instead indicate a much higher fishing mortality (mortality induced by legal professional fishery) rates and a considerably smaller eel biomass.

Description: Discard bans have been proposed as part of management policies aimed at balanced harvest (BH). Nationwide discard bans exist in several countries, including Chile, the European Union, Norway, and New Zealand. We analysed experiences from these countries to determine whether or not discard bans are in contradiction with BH, based on six aspects: policy objectives, species/sizes applicability, accompanying technical measures, at-sea monitoring and control, and possible impacts. When discard bans are fully implemented, fishing operations change to more selective fishing, typically targeting bigger individuals of main commercial species. This is consistent with the primary objective of many discard policies, i.e. to reduce unwanted catch. In contrast, proponents of BH argue that broader catch diversity, a product of a widespread harvest strategy, should be sought to avoid major impacts on the ecosystem. Our analysis demonstrates that the scope of discard bans is often limited to main commercial species, although usually they can be extended to include more ecosystem components. Some of the policies examined also prohibit the use of unwanted catches for human consumption, thus limiting their effective use. However, the implementation of discard bans requires high levels of at-sea monitoring and effective control, and/or strong incentives to fish more selectively, neither of which applied in most cases examined. We conclude that if discard bans were set differently, they could contribute to fishery management policies aiming at BH. Their goals should be in line with BH, i.e. to reach a wider global harvest pattern, or at least be established within management regimes that promote high compliance. Finally, the extent to which a discard ban contributes to achieve BH depends also on the relative importance of the ecosystem benthic and megafauna components.

Description: In the context of the ASAI (Astrochemical Surveys At IRAM) project, we carried out an unbiased spectral survey in the millimetre window towards the well known low-mass Class I source SVS13-A. The high sensitivity reached (3–12 mK) allowed us to detect at least six HDO broad (full width at half-maximum ~4–5 km s –1 ) emission lines with upper level energies up to E u = 837 K. A non-local thermodynamic equilibrium Large Velocity Gradient (LVG) analysis implies the presence of very hot (150–260 K) and dense (≥3  x  10 7  cm –3 ) gas inside a small radius (~25 au) around the star, supporting, for the first time, the occurrence of a hot corino around a Class I protostar. The temperature is higher than expected for water molecules are sublimated from the icy dust mantles (~100 K). Although we cannot exclude we are observing the effects of shocks and/or winds at such small scales, this could imply that the observed HDO emission is tracing the water abundance jump expected at temperatures ~220–250 K, when the activation barrier of the gas phase reactions leading to the formation of water can be overcome. We derive X ( HDO ) ~ 3  x  10 –6 , and a H 2 O deuteration ≥1.5  x  10 –2 , suggesting that water deuteration does not decrease as the protostar evolves from the Class 0 to the Class I stage.

Description: Evidence for the presence of quasi-periodic oscillations (QPOs) in the optical polarization of the blazar PKS 2155–304, during a period of enhanced gamma-ray brightness, is presented. The periodogram of the polarized flux revealed the existence of a prominent peak at T ~ 13 min, detected at 〉99.7 per cent significance, and T ~ 30 min, which was nominally significant at 〉99 per cent. This is the first evidence of QPOs in the polarization of an active galactic nucleus, potentially opening up a new avenue of studying this phenomenon.

Description: Experimental studies of mantle petrology find that small concentrations of water and carbon dioxide have a large effect on the solidus temperature and distribution of melting in the upper mantle. However, it has remained unclear what effect small fractions of deep, volatile-rich melts have on melt transport and reactive melting in the shallow asthenosphere. Here we present theory and computations indicating that low-degree, reactive, volatile-rich melts cause channelization of magmatic flow at depths approximately corresponding to the anhydrous solidus temperature. These results are obtained with a novel method to simulate the thermochemical evolution of the upper mantle in the presence of volatiles. The method uses a thermodynamically consistent framework for reactive, disequilibrium, multi-component melting. It is coupled with a system of equations representing conservation of mass, momentum, and energy for a partially molten grain aggregate. Application of this method in two-phase, three-component upwelling-column models demonstrates that it reproduces leading-order features of hydrated and carbonated peridotite melting; in particular, it captures the production of low-degree, volatile-rich melt at depths far below the volatile-free solidus. The models predict that segregation of volatile-rich, deep melts promotes a reactive channelling instability that creates fast and chemically isolated pathways of melt extraction. Reactive channelling occurs where volatile-rich melts flux the base of the silicate melting region, enhancing dissolution of fusible components from the ambient mantle. We find this effect to be similarly expressed for models of both hydrated and carbonated mantle melting. These findings indicate that despite their small concentrations, water and carbon dioxide have an important control on the extent and style of magma genesis, as well as on the dynamics of melt transport.

Description: The spectrum and morphology of the diffuse Galactic -ray emission carries valuable information on cosmic ray (CR) propagation. Recent results obtained by analyzing Fermi -LAT data accumulated over 7 yr of observation show a substantial variation of the CR spectrum as a function of the distance from the Galactic Centre. The spatial distribution of the CR density in the outer Galaxy appears to be weakly dependent upon the galactocentric distance, as found in previous studies as well, while the density in the central region of the Galaxy was found to exceed the value measured in the outer Galaxy. At the same time, Fermi -LAT data suggest a gradual spectral softening while moving outwards from the centre of the Galaxy to its outskirts. These findings represent a challenge for standard calculations of CR propagation based on assuming a uniform diffusion coefficient within the Galactic volume. Here, we present a model of non-linear CR propagation in which transport is due to particle scattering and advection off self-generated turbulence. We find that for a realistic distribution of CR sources following the spatial distribution of supernova remnants and the space dependence of the magnetic field on galactocentric distance, both the spatial profile of CR density and the spectral softening can easily be accounted for.

Description: The correlation between the frequency and the absolute value of the frequency derivative of the kilohertz quasi-periodic oscillations (QPOs) observed for the first time from 4U 1636-53 is a simple consequence and indicator of the existence of a non-Keplerian rotation rate in the accretion disc boundary layer. This Letter interprets the observed correlation, showing that the observations provide strong evidence in support of the fundamental assumption of disc accretion models around slow rotators, that the boundary layer matches the Keplerian disc to the neutron star magnetosphere.

Description: Energy allocation models have proved useful for clarifying the ecological mechanisms which influence growth and reproduction schemes in species with indeterminate growth and for understanding how traits correlate with generate the life history of specific species. In view of the need to understand how exploitation affects species for which few data on key population parameters such as reproductive potential and population growth rate are available, it would be helpful if simple energy allocation schemes parametrized by easily obtainable data could be used to estimate parameters such as reproductive effort and output. Testing the predictions of three such models on fecundity data from a range of species, we show how the simplifications required in a generalized energy allocation scheme are reflected in the deviations between model predictions and empirical data, and discuss the validity of the assumptions underlying these models. We caution against over-reliance on generalized and simplified models to predict reproductive effort.

Description: Since 2007, the biomass of sardine and anchovy in the NW Mediterranean has remained persistently low, whereas the biomass of the commercially low-valued sprat has exploded. Also, simultaneous decreases in condition, size, and/or age of these populations were observed. Altogether, this resulted in a drop in landings of small pelagics. To understand the amplitude of these events and to provide a baseline scenario against which current changes can be compared, we compiled exceptionally long landing series (1865–2013) of sardine, anchovy, and mackerel for different subregions of the southern French coast. We characterized the fluctuations of these landings and compared these with environmental drivers (sea surface temperature, Rhône river discharge, North Atlantic Oscillation, Western Mediterranean Oscillation—WeMO, and Atlantic Multidecadal Oscillation—AMO), using different time-series analyses. We also collated historical data to infer qualitative changes in fishing effort over time. A fishing effort related increase in landings was observed around 1962 for all three species, although current sardine landings have dropped below levels observed before this period. Sardine and anchovy landings were, respectively, positively and negatively related to the AMO index and anchovy landings were also positively related to the WeMO. We finished by discussing the potential role of the environmental variables and fishing on long-term fishery landings trends.

Description: We examine whether the landing rates of Belgian beam trawlers in the Southern Bight of the North Sea were affected through competitive interactions with the Dutch beam trawler fleet and whether the development of a pulse trawler fleet has altered competitive interactions between both fleets. Effects of competition were investigated through a natural experiment based on the different weekly exploitation patterns of both fleets. Logbook data were used to fit a generalized additive mixed model for the daily landing rates of the target species sole ( Solea solea ) and plaice ( Pleuronectes platessa ). Results showed that landing rates of sole by the Belgian beam trawlers (〉221 kW) from 2006 to 2013 were lower during weekdays than during weekends when the Dutch trawler fleet is in harbour, while no such an effect was found for plaice. After the development of a pulse trawler fleet in 2011, the negative weekday effect in the sole landing rates was much more pronounced in 2012 and 2013. This increased loss of efficiency during weekdays, as a result of increased competition with the Dutch trawler fleet, coincided with a reallocation of fishing effort by the Belgian beam trawler fleet.

Description: Fishers' knowledge research (FKR) aims to enhance the use of experiential knowledge of fish harvesters in fisheries research, assessment, and management. Fishery participants are able to provide unique knowledge, and that knowledge forms an important part of "best available information" for fisheries science and management. Fishers' knowledge includes, but is much greater than, basic biological fishery information. It includes ecological, economic, social, and institutional knowledge, as well as experience and critical analysis of experiential knowledge. We suggest that FKR, which may in the past have been defined quite narrowly, be defined more broadly to include both fishery observations and fishers "experiential knowledge" provided across a spectrum of arrangements of fisher participation. FKR is part of the new and different information required in evolving "ecosystem-based" and "integrated" management approaches. FKR is a necessary element in the integration of ecological, economic, social, and institutional considerations of future management. Fishers' knowledge may be added to traditional assessment with appropriate analysis and explicit recognition of the intended use of the information, but fishers' knowledge is best implemented in a participatory process designed to receive and use it. Co-generation of knowledge in appropriately designed processes facilitates development and use of fishers' knowledge and facilitates the participation of fishers in assessment and management, and is suggested as best practice in improved fisheries governance.

Description: The origin and life history of 186 Atlantic salmon caught at sea within Icelandic waters were investigated using microsatellites to assess the origin and scales and otoliths to assess freshwater and sea age. A total of 184 samples were aged using scales or otolithes or both. Most of the samples were from individuals in their first year at sea (72.8%). The freshwater age varied from 1 to 5 years with an average of 2.6 years. The most common freshwater age was 2 years (42%), with a further substantial proportion of 3-year-old fish (28%). Genetic assignment of individual fish to their most likely population of origin was performed using Bayesian genetic individual assignments with a baseline consisting of 284 Eastern Atlantic rivers and 466 sample sites genotyped at the 14 microsatellite. A total of 186 samples of salmon caught at sea were assigned to their origin. Eight samples, from post-smolts and caught close to land, were assigned as having come from Iceland. Of the remaining 178 samples, 121 individuals (68%) were from the Southern Group, i.e. from mainland Europe, the UK, and Ireland, 53 individuals (30%) were from the Northern Group, i.e. Scandinavia and Northern Russia, and 4 individuals were from Iceland (2%). Stock mixture proportions were estimated for four periods using ONCOR and cBAYES. Stock mixture analysis generally supported the individual assignments, but did not suggest a seasonal component to the distribution of salmon stocks. These results indicate that the sea south and east of Iceland are important as feeding areas for migrating Atlantic salmon, particularly for salmon originating in the UK, Ireland, and southern Europe. Furthermore, the lack of adult Icelandic fish so close to Iceland is remarkable and suggests that Atlantic salmon from Icelandic stocks are using different feeding grounds.

Description: Demands for management advice on mixed and multispecies fisheries pose many challenges, further complicated by corresponding requests for advice on the environmental impacts of alternate management options. Here, we develop, and apply to North Sea fisheries, a method for collectively assessing the effects of, and interplay between, technical interactions, multispecies interactions, and the environmental effects of fishing. Ecological interactions involving 21 species are characterized with an ensemble of 188 plausible parameterizations of size-based multispecies models, and four fleets (beam trawl, otter trawl, industrial, and pelagic) characterized with catch composition data. We use the method to evaluate biomass and economic yields, alongside the risk of stock depletion and changes in the value of community indicators, for 10 000 alternate fishing scenarios (combinations of rates of fishing mortality F and fleet configuration) and present the risk vs. reward trade-offs. Technical and multispecies interactions linked to the beam and otter trawl fleets were predicted to have the strongest effects on fisheries yield and value, risk of stock collapse and fish community indicators. Increasing beam trawl effort led to greater increases in beam trawl yield when otter trawl effort was low. If otter trawl effort was high, increases in beam trawl effort led to reduced overall yield. Given the high value of demersal species, permutations of fleet effort leading to high total yield (generated primarily by pelagic species) were not the same as permutations leading to high catch values. A transition from F for 1990 to 2010 to F MSY , but without changes in fleet configuration, reduced risk of stock collapse without affecting long-term weight or value of yield. Our approach directly addresses the need for assessment methods that treat mixed and multispecies issues collectively, address uncertainty, and take account of trade-offs between weight and value of yield, state of stocks and state of the environment.

Description: Underwater video recordings in the mouth of a squid trawl were used to evaluate the effectiveness of a trawl configured with drop-chain groundgear to catch longfin inshore squid ( Doryteuthis pealeii ) and reduce bycatch of finfish in the Nantucket Sound squid fishery off Cape Cod, Massachusetts, USA. Entrance through the trawl mouth or escape underneath the fishing line and between drop chains was quantified for targeted squid, and two major bycatch species, summer flounder ( Paralichthys dentatus ) and skates (family Rajidae). Additionally, contact and impingement between animals and groundgear were also quantified. Fish and squid swimming behaviours, positions, orientations, and time in the trawl mouth were quantified and related to capture or escape at the trawl mouth. Squid entered the trawl singly and in schools, and no squid were observed escaping under the fishing line. Most squid entered the trawl in the upper portion of the trawl mouth; mantle orientated away from the trawl and swimming in the same direction, and were gradually overtaken, not actively attempting to escape. Summer flounder and skates were observed to remain on or near the seabed, orientated, and swimming in the same direction as the approaching trawl. The majority (60.5%) of summer flounder entered the trawl above the fishing line. Summer flounder that changed their orientation and turned 180° were significantly more likely to enter the trawl ( p 〈 0.05). Most skates (89.7%) avoided trawl entrance and escaped under the fishing line. Neither squid nor summer flounder were observed to make contact or become impinged to the groundgear; however, 35.4% of skates had substantial contact with groundgear, with 12.3% becoming impinged. Video analysis results showed that the drop-chain trawl is effective at retaining targeted squid while allowing skates to escape. However, it is ineffective at avoiding the capture of summer flounder.

Description: During their formation phase, stars gain most of their mass in violent episodic accretion events, such as observed in FU Orionis (FUor) and EXor stars. V346 Normae is a well-studied FUor that underwent a strong outburst beginning around 1980. Here, we report on photometric and spectroscopic observations, which show that the visual/near-infrared brightness has decreased dramatically between the 1990s and 2010 ( R 10.9 mag, J 7.8 mag and K 5.8 mag). The spectral properties of this fading event cannot be explained by variable extinction alone, but indicate a drop in accretion rate by two to three orders of magnitude. This is the first time that a member of the FUor class has been observed to switch to a very low accretion phase. Remarkably, in the last few years (2011–2015) V346 Nor has brightened again at all near-infrared wavelengths, indicating the onset of a new outburst event. The observed behaviour might be consistent with the clustered luminosity bursts that have been predicted by recent gravitational instability and fragmentation models for the early stages of protostellar evolution. Given V346 Nor's unique characteristics (concerning outburst duration, repetition frequency and spectroscopic diagnostics), our results also highlight the need to revisit the FUor/EXor classification scheme.