The Soft X-ray Imager(SXI)on the SMILE Mission

The Soft X-ray Imager(SXI)is part of the scientific payload of the Solar wind Magnetosphere Ionosphere Link Explorer(SMILE)mission.SMILE is a joint science mission between the European Space Agency(ESA)and the Chinese Academy of Sciences(CAS)and is due for launch in 2025.SXI is a compact X-ray telescope with a wide field-of-view(FOV)capable of encompassing large portions of Earth’s magnetosphere from the vantage point of the SMILE orbit.SXI is sensitive to the soft X-rays produced by the Solar Wind Charge eXchange(SWCX)process produced when heavy ions of solar wind origin interact with neutral particles in Earth’s exosphere.SWCX provides a mechanism for boundary detection within the magnetosphere,such as the position of Earth’s magnetopause,because the solar wind heavy ions have a very low density in regions of closed magnetic field lines.The sensitivity of the SXI is such that it can potentially track movements of the magnetopause on timescales of a few minutes and the orbit of SMILE will enable such movements to be tracked for segments lasting many hours.SXI is led by the University of Leicester in the United Kingdom(UK)with collaborating organisations on hardware,software and science support within the UK,Europe,China and the United States.

Blob properties in I-mode and ELM-free H-mode compared to L-mode on EAST

The blob properties in I-mode and ELM-free H-mode plasmas compared to L-mode have been investigated on the EAST tokamak,including the blob detection rate Nb,sizeδb,lifetimeτb and radial velocity vr,b.The blob properties in L-mode and I-mode are similar,and those in ELM-free H-mode are different to them.The blob Nbis smaller whileτbis larger in H-mode.The experimental blob sizeδband velocity scalings vr,b-δb show a good agreement with the theoretical models.The variation in blob properties during the L-I and H-L transitions,and their relations to the scrape-off layer(SOL)density,edge and SOL turbulence,and SOL collisionality are discussed.The suppression of the edge(inside the last closed flux surface)turbulence is not reflected in the blob behavior,while the blob detection rate shows a correlation with the SOL density and its low-frequency(3–50 kH z)fluctuations.In addition,the blob detection rate is found to increase with the divertor collisionalityΛdiv,indicating a dependence of blob behavior onΛdiv.The differences in blob detection rates among the three operating regimes might be due to their different SOL densities and collisionalities.The investigation contributes to understanding the influences of edge and SOL plasma parameters on the blob behavior.

Advanced Alumina and Zirconia Ceramics Produced by the Electroconsolidation Method

The possibility to produce advanced alumina and zirconia ceramics by the electroconsolidation method is studied. The technological parameters of Al2O3 and ZrO2 （3 mass% Y2O3 ） production were developed and optimized. Electroconsolidated alumina and zirconia ceramics have higher values of properties in comparison with ordinary sintered samples in air. Advanced proper- ties of electroconsolidated ceramics are defined by homo- geneous, ultradense and fine-crystalline structure that was formed due to the effect to consolidate the materials to high density for a shortest time.

Compressive Measurement Identification of Linear Time-Invariant System Application in DC Motor

In traditional system identification (SI), actual values of system parameters are concealed in the input and output data;hence, it is necessary to apply estimation methods to determine the parameters. In signal processing, a signal with N elements must be sampled at least N times. Thus, most SI methods use N or more sample data to identify a model with N parameters;however, this can be improved by a new sampling theory called compressive sensing (CS). Based on CS, an SI method called compressive measurement identification (CMI) is proposed for reducing the data needed for estimation, by measuring the parameters using a series of linear measurements, rather than the measurements in sequence. In addition, the accuracy of the measurement process is guaranteed by a criterion called the restrict isometric principle. Simulations demonstrate the accuracy and robustness of CMI in an underdetermined case. Further, the dynamic process of a DC motor is identified experimentally, establishing that CMI can shorten the identification process and increase the prediction accuracy.

Experimental investigation of scrape-off layer blob high density transition in L-mode plasmas on EAST

Lithium Beam Emission Spectroscopy systems in the outer midplane and divertor Langmuir probe arrays embedded in the divertor target plates,are utilized to investigate the scrape-off layer(SOL)blob transition and its relation with divertor detachment on EAST.The blob transition in the near SOL is observed during the density ramp-up phase.When the plasma density,normalized to the Greenwald density limit,exceeds a threshold of f_(GW)~0.5,the blob size and lifetime increases by 2–3 times,while the blob detection rate decreases by about 2 times.In addition,a weak density shoulder is observed in the near SOL region at the same density threshold.Further analysis indicates that the divertor detachment is highly correlated with the blob transition,and the density threshold of blob transition is consistent with that of the access to the outer divertor detachment.The potential physical mechanisms are discussed.These results could be useful for the understanding of plasma-wall interaction issues in future devices that will operate under a detached divertor and high density conditions(over the blob transition threshold).

Divertor detachment operation in helium plasmas with ITER-like tungsten divertor in EAST

Detachment in helium(He)discharges has been achieved in the EAST superconducting tokamak equipped with an ITER-like tungsten divertor.This paper presents the experimental observations of divertor detachment achieved by increasing the plasma density in He discharges.During density ramp-up,the particle flux shows a clear rollover,while the electron temperature around the outer strike point is decreasing simultaneously.The divertor detachment also exhibits a significant difference from that observed in comparable deuterium(D)discharges.The density threshold of detachment in the He plasma is higher than that in the D plasma for the same heating power,and increases with the heating power.Moreover,detachment assisted with neon(Ne)seeding was also performed in L-and H-mode plasmas,pointing to the direction for reducing the density threshold of detachment in He operation.However,excessive Ne seeding causes confinement degradation during the divertor detachment phase.The precise feedback control of impurity seeding will be performed in EAST to improve the compatibility of core plasma performance with divertor detachment for future high heating power operations.

Investigation of the interaction of material of fuel cladding for WWER-1000 reactor with steam at a temperature of accident overheatings

The subject of this study is the oxidation of fuel rod cladding made of material Zr1Nb(0.1% O) in steam at temperatures in the range of 660℃ to 1200℃ with a surface in the initial state (after manufacturing - grinding) and after additional chemical etching. The changes in the microstructure of tubes due to the interaction with steam were investigated. A comparison was made between the oxidation rate of this material (weight gain) and the data on the oxidation of other alloys for nuclear power plants. The oxidation rate of Zr1Nb(0.1% O) is close to the oxidation rate of other zirconium alloys. It is shown that after chemical treatment of the surface of the samples there is a more even growth of oxide films, and they have a smaller thickness for the same time of exposure than after mechanical grinding. Surface treatment before oxidation also affects the change of microstructure of samples when heated to high temperatures.

Scientific challenges and instrumentation for the International Meridian Circle Program

Earth’s ecosystems and human activities are threatened by a broad spectrum of hazards of major importance for the safety of ground infrastructures,space systems and space flight:solar activity,earthquakes,atmospheric and climatic disturbances,changes in the geomagnetic field,fluctuations of the global electric circuit.Monitoring and understanding these major hazards to better predict and mitigate their effects is one of the greatest scientific and operational challenges of the 21st century.Though diverse,these hazards share one feature in common:they all leave their characteristic imprints on a critical layer of the Earth’s environment:its ionosphere,middle and upper atmosphere(IMUA).The objective of the International Meridian Circle Program(IMCP),a major international program led by the Chines Academy of Sciences(CAS),is to deploy,integrate and operate a global network of research and monitoring instruments to use the IMUA as a screen on which to detect these imprints.In this article,we first show that the geometry required for the IMCP global observation system leads to a deployment of instruments in priority along the 120°E-60°W great meridian circle,which will cover in an optimal way both the dominant geographic and geomagnetic latitude variations,possibly complemented by a second Great Circle along the 30°E-150°W meridians to capture longitude variations.Then,starting from the Chinese Meridian Project(CMP)network and using it as a template,we give a preliminary and promising description of the instruments to be integrated and deployed along the 120°E-60°W great circle running across China,Australia and the Americas.

互花米草有利于我国海岸带蓝碳功能提升

Spartina alterniflora has rapidly and extensively encroached on China's coastline over the past decades.Among the coastal areas invaded by S.alterniflora,at most 93%are mudflats.However,the effect of S.alterniflora invasion on soil organic carbon(SOC)stocks of coastal mudflats has not been systematically studied on a national scale.Here,we quantified the nationwide changes in SOC stocks in coastal mudflats associated with S.alterniflora invasion between 1990 and 2020.We found that S.alterniflora invasion significantly enhanced SOC stocks in coastal China.Nonetheless,the benefit of S.alterniflora invasion of coastal SOC stock may be weakened by continuing human intervention.We found that S.alterniflora invading mudflats added 2.3 Tg SOC stocks to China's coastal blue carbon,while 1.78 Tg SOC stocks were lost mainly due to human activities,resulted in a net SOC stock gain of 0.52 Tg C.These findings overturned the traditionally thought that S.alterniflora invasion would reduce ecosystem services by highlighting that the historical invasion of S.alterniflora has broadly and consistently enhanced blue carbon stock in coastal China.

Anthropogenic land use substantially increases riverine CO_(2) emissions

Carbon dioxide(CO_(2)) emissions from inland waters to the atmosphere are a pivotal component of the global carbon budget. Anthropogenic land use can influence riverine CO_(2) emissions, but empirical data exploring cause-effect relationships remain limited. Here, we investigated CO_(2) partial pressures(pCO_(2)) and degassing in a monsoonal river(Yue River)within the Han River draining to the Yangtze in China. Almost 90% of river samples were supersaturated in CO_(2) with a mean ± standard deviation of 1474 ± 1614 μatm, leading to emissions of 557-971 mmol/m^(2)/day from river water to the atmosphere. Annual CO_(2) emissions were 1.6-2.8 times greater than the longitudinal exports of riverine dissolved inorganic and organic carbon. pCO_(2) was positively correlated to anthropogenic land use(urban and farmland), and negatively correlated to forest cover. p CO_(2) also had significant and positive relationships with total dissolved nitrogen and total dissolved phosphorus. Stepwise multiple regression models were developed to predict p CO_(2) . Farmland and urban land released nutrients and organic matter to the river system, driving riverine p CO_(2) enrichment due to enhanced respiration in these heterotrophic rivers. Overall, we show the crucial role of land use driving riverine pCO_(2) , which should be considered in future large-scale estimates of CO_(2) emissions from streams. Land use change can thus modify the carbon balance of urban-river systems by enhancing river emissions, and reforestation helps carbon neutral in rivers.

HMMR alleviates endoplasmic reticulum stress by promoting autophagolysosomal activity during endoplasmic reticulum stress-driven hepatocellular carcinoma progression

Background The mechanism of hepatitis B virus(HBV)-induced carcinogenesis remains an area of interest.The accumulation of hepatitis B surface antigen in the endoplasmic reticulum(ER)of hepatocytes stimulates persistent ER stress.Activity of the unfolded protein response(UPR)pathway of ER stress may play an important role in inflammatory cancer transformation.How the protective UPR pathway is hijacked by cells as a tool for malignant transformation in HBV-related hepatocellular carcinoma(HCC)is still unclear.Here,we aimed to define the key molecule hyaluronan-mediated motility receptor(HMMR)in this process and explore its role under ER stress in HCC development.Methods An HBV-transgenic mouse model was used to characterize the pathological changes during the tumor progression.Proteomics and transcriptomics analyses were performed to identify the potential key molecule,screen the E3 ligase,and define the activation pathway.Quantitative real-time PCR and Western blotting were conducted to detect the expression of genes in tissues and cell lines.Luciferase reporter assay,chromatin immunoprecipitation,coimmunoprecipitation,immunoprecipitation,and immunofluorescence were employed to investigate the molecular mechanisms of HMMR under ER stress.Immunohistochemistry was used to clarify the expression patterns of HMMR and related molecules in human tissues.Results We found sustained activation of ER stress in the HBV-transgenic mouse model of hepatitis-fibrosis-HCC.HMMR was transcribed by c/EBP homologous protein(CHOP)and degraded by tripartite motif containing 29(TRIM29)after ubiquitination under ER stress,which caused the inconsistent expression of mRNA and protein.Dynamic expression of TRIM29 in the HCC progression regulated the dynamic expression of HMMR.HMMR could alleviate ER stress by increasing autophagic lysosome activity.The negative correlation between HMMR and ER stress,positive correlation between HMMR and autophagy,and negative correlation between ER stress and autophagy were verified in human tissues.Conclusions This study identified the complicated role of HMMR in autophagy and ER stress,that HMMR controls the intensity of ER stress by regulating autophagy in HCC progression,which could be a novel explanation for HBV-related carcinogenesis.

Phase-Controlled 1T Transition-Metal Dichalcogenide-Based Multidimensional Hybrid Nanostructures

Metallic-phase transition-metal dichalcogenides(TMDCs)exhibit unusual physicochemical properties compared with their semiconducting counterparts.However,they are thermodynamically unstable to access and it is even more challenging to construct their metastable-phase heterostructures.Herein,we demonstrate a general solution protocol for phase-controlled synthesis of distorted octahedral 1T WS2-based(1T structure denotes an octahedral coordination for W atom)multidimensional hybrid nanostructures from two-dimensional(2D),one-dimensional(1D),and zero-dimensional(0D)templates.This is realized by tuning the reactivity of tungsten precursor and the interaction between crystal surface and ligands.As a conceptual study on crystal phase-and dimensionality-dependent applications,we find that the three-dimensional(3D)hierarchical architectures achieved,comprising 1T WS2 and 2D Ni3S4,are very active and stable for catalyzing hydrogen evolution.Our results open up a new way to rationally design phase-controlled nanostructures with increased complexity and more elaborate functionalities.

Optimising mesh size with escape gaps in a dual-species portunid-trap fishery

In south-eastern Australia,the same baited,round traps(comprising 50–57-mm mesh netting)are used to target giant mud,Scylla serrata and blue swimmer crabs,Portunus armatus in spatially separated fisheries.Both fisheries are characterised by the common,problematic discarding of undersized portunids(<85 and 65 mm carapace length;CL for S.serrata and P.armatus)and fish(yellowfin bream,Acanthopagrus australis).This poor selectivity was addressed here in two experiments assessing the utility of(1)traps partially or completely covered in larger mesh(91 mm to match the minimum legal size of the smaller P.armatus),and then(2)any cumulative benefits of fitting species-specific escape gaps.In experiment 1,there were no differences among catches of legal-sized portunids associated with either partial,or complete trap coverage with larger mesh.Irrespective of mesh coverage,both designs of 91-mm traps also retained significantly fewer(by up to 42%)undersized P.armatus and A.australis.In experiment 2,replicate traps completely covered in 91-mm mesh were tested against conventional traps comprising 56-mm mesh,and traps with the same mesh sizes,but also three escape gaps configured for either S.serrata(46×120 mm)or P.armatus(36×120 mm)(i.e.four treatments in total).All modified traps maintained catches of legal-sized S.serrata,and only the 91-mm traps with escape gaps caught fewer legal-sized P.armatus.Fewer undersized S.serrata,P.armatus and A.australis(mean catches reduced by up to 49%)were retained in all larger-meshed than small-meshed traps,and in all of those traps with escape gaps(by up to 95%)than without.While there were no significant cumulative benefits of escape gaps in largermeshed traps(measured by a statistical interaction),there was a trend of fewer unwanted catches overall.These data support configuring portunid traps with mesh sizes matching the morphology of the smallest legal-sized target species.But,simply retroactively fitting escape gaps in existing,smaller-meshed traps will also realize positive selectivity benefits.

Coastal blue carbon in China as a nature-based solution toward carbon neutrality

To achieve the Paris Agreement,China pledged to become“Carbon Neutral”by the 2060s.In addition to massive decarbonization,this would require significant changes in ecosystems toward negative CO_(2)emissions.The ability of coastal blue carbon ecosystems(BCEs),including mangrove,salt marsh,and seagrass meadows,to sequester large amounts of CO_(2)makes their conservation and restoration an important“nature-based solution(NbS)”for climate adaptation and mitigation.In this review,we examine how BCEs in China can contribute to climate mitigation.On the national scale,the BCEs in China store up to 118 Tg C across a total area of 1,440,377 ha,including over 75%as unvegetated tidal flats.The annual sedimental C burial of these BCEs reaches up to 2.06 Tg C year^(−1),of which most occurs in salt marshes and tidal flats.The lateral C flux of mangroves and salt marshes contributes to 1.17 Tg C year^(−1)along the Chinese coastline.Conservation and restoration of BCEs benefit climate change mitigation and provide other ecological services with a value of$32,000 ha^(−1)year^(−1).The potential practices and technologies that can be implemented in China to improve BCE C sequestration,including their constraints and feasibility,are also outlined.Future directions are suggested to improve blue carbon estimates on aerial extent,carbon stocks,sequestration,and mitigation potential.Restoring and preserving BCEs would be a cost-effective step to achieve Carbon Neutral by 2060 in China despite various barriers that should be removed.

Land degradation and integrated watershed management in India

In view of the stagnating productivity levels of irrigated agriculture,the contribution from rainfed agriculture should be increased to meet the requirements from the ever growing human and animal population of India.Land degradation is a major threat to our food and environment security and the extent of degradation problems are more pronounced in rainfed regions.Large potential of rainfed agriculture is untapped largely due to lack of enabling policy support and investments.In drought-prone rainfed areas,watershed management has shown the potential of doubling the agricultural productivity,increase in water availability,restoration of ecological balance in the degraded rainfed ecosystems by greening these areas and diversification of cropping farming systems.Impact of various watershed programmes can be substantially enhanced by developing new approaches and enabling policies new paradigm based on learnings over last 30 years for people-centric holistic watershed management involving convergence,collective action,consortium approach,capacity development to address equity,efficiency,environment and economic concerns is urgently needed.However,this can be used as entry point activity for improving livelihood for rural community.It has been realized that for sustainable developments of degraded lands,involvement of people(land less and beneficiaries)is very much essential.For the last decade efforts have been made institutionalize the organizations of the community&beneficiaries and ensuring their involvement in planning project formulation,implementation and maintenance.Government of India has launched various centre-sector,state-sector and foreign aided schemes for prevention of land degradation,reclamation of special problem areas for ensuring productivity of the land,preservation of land resources and improvement of ecology and environment.These schemes are being implemented on watershed basis in rainfed areas.Soil conservation measures and reclamation of degraded lands are decided considering the land capability and land uses.The efforts made so far resulted in enhancement of agricultural production and productivity of lands,increase in employment generation,improving the environment of the areas and socio-economic upgradation of the people.Integrated watershed management approach has been adopted as a key national strategy for sustainable development of rural areas.This has been proved by conducting monitoring and impact evaluation studies of the integrated watershed projects by external agencies.

Refining tickler chains for penaeid trawls

Tickler chains are simple additions to the ground gears of benthic trawls that can improve the catches of some target species,albeit with considerable variability.The purpose of this study was to decipher some of the technical variability associated with tickler chains used with generic,paired trawls targeting school prawns,Metapenaeus macleayi.In the first of two experiments,single tickler chains were either attached between the trawl otter boards or the wing ends and compared against each other and a control trawl(no tickler chain).Attaching the tickler chain to the otter boards significantly reduced wing-end spread and the trawled area without significantly affecting catches of school prawns.By comparison,attaching the tickler chain to the wing ends maintained spread and resulted in significantly more school prawns being caught(by 1.11×)than in the control trawl,and also fewer numbers of one teleost species,pink-breasted siphonfish,Siphamia roseigaster.In experiment two,a single tickler chain was compared against one with multiple chains and one with a double chain;all attached at the wing ends.Trawls with the multiple-and double-tickler chains had the same wing-end spread as those with the single tickler chain,while retaining up to 1.17×more school prawns,and for the double-chain tickler,45%fewer southern herring,Herklotsichthys castelnaui.The results are attributed to mechanical and visual stimuli affecting school prawns and some fish,respectively,and support maximising the surface area of tickler chains within the wing ends as a means for improving penaeid-trawl species selectivity without affecting swept area.

Improving penaeid-trawl efficiencies via ground gear with tickler chains

Penaeid trawls often have poor ecological efficiencies measured as unwanted bycatches(with high discard mortality)and<100%effectiveness for all penaeids interacting with the ground gear(with some escape mortality).This study investigated the utility of varying ground-chain size(8-vs 10-mm diameter(Ø)stainless-steel chain)and the present or absence of a tickler chain(4-mmØ)for improving efficiencies an Australian fishery diurnally targeting school,Metapenaeus macleayi and eastern king prawns,Penaeus plebejus.There were no treatment effects on wing-end spread and therefore areas trawled.Irrespective of the tickler chain,increasing the ground-chainØreduced catches of total penaeids(by 14%)and jellyfish,Catostylus mosaicus(by 39%)-results speculatively attributed to variation in ground contact and/or a slightly higher footrope in trawls with the 10-mmØchain.By comparison,installing the tickler chain had no effect on eastern king prawns,but increased catches of school prawns(by 1.13×)and bycatches of blue swimmer crabs,Portunus armatus(1.52×;a species with a low discard mortality)and jellyfish(1.23×),while reducing bycatches of two species with high discard mortalities:southern herring,Herklotsichthys castelnaui(by 38%)and squid,Uroteuthis sp.(37%).The results were attributed to the tickler chain producing(1)mechanical stimuli that augmented the capture of benthic-orientated school prawns(but not eastern king prawns owing to diel variations in emergence from the substrata),blue swimmer crabs and jellyfish;and(2)visual stimuli that possibly enabled some southern herring and squid to detect the trawl and escape.The data show tickler chains can improve trawl efficiency for penaeids with at least some positive effects on bycatch that should be rationalised in terms of species-specific vulnerabilities to unaccounted fishing mortality.

Using tickler chains to promote more environmentally benign trawls in an Australian penaeid fishery

There has been an increasing emphasis on reducing the environmental impacts of penaeid trawls by modifying their anterior sections.In one Australian estuary,this approach has culminated in a new generic trawl comprising a slightly smaller mesh size,and steeper and shorter side panels than traditional trawls,combined with a top panel extending forwards of the bottom panel(termed‘lead-ahead’)and no headline floats.This study sought to investigate if an additional simple,cumulative modification(tickler chain)might help promote adoption of the new trawl,via improved penaeid catches.Six volunteer fishers towing pairs of either the traditional or new trawls in double rigs were asked if an observer could accompany fishing trips,and alternately attach a light tickler chain(~3 kg)anterior to the ground gear of one trawl.Regardless of the trawl design,the tickler chains significantly increased the catch weights of penaeids,but relatively more so in the new trawls(by 1.11×vs 1.08×).The tickler chains also significantly increased the number and weight of total bycatch in the traditional trawls(by up to 1.22×),but not in the new trawls-although there were variable species-specific effects.In terms of total effects,the data support using tickler chains to increase the efficiency of the new trawls and their cumulative benefits,and could be promoted to facilitate broader inter-and intra-fleet adoption.

Effects of twine material on the marine debris and relative ghost fishing of portunid hoop (tangle) nets

Portunids are important to recreational fisheries in Australia and typically are harvested by baited gears.Most of these baited gears are considered environmentally benign,although small conical hoop(tangle)nets fished in southeastern Australia sometimes are damaged and lose twine,which becomes marine debris.Substituting conventional multifilament polyamide(PA)twine with alternative multi-monofilament and monofilament PA twines in hoop nets can dramatically reduce marine debris,but there remain unanswered questions concerning the relative fishing power of alternative twines among derelict hoop nets.This study addresses the shortfall in data by comparing the efficiencies and damage to replicate hoop nets made from the three twines and left to fish for short(one and two days),medium(three to five days)and long(ten and fourteen days)soaks.Irrespective of twine material or soak time,all hoop nets entangled the same numbers of giant mud crabs,Scylla serrata implying catch saturation within two days.Only four other animals were caught(all yellowfin bream,Acanthopagrus australis)and all died.At least some replicates of all hoop nets were damaged and lost twine,but this was greatest among the multifilament(up to a maximum of 9.3m hoop-net deployment−1),followed by the multi-monofilament(up to 7.4m hoop-net deployment−1)and monofilament hoop nets(1.4m hoop-net deployment−1).Replacing the existing multifilament twine in hoop nets with monofilament when targeting S.serrata would maintain catches and minimise marine debris during conventional soaks,without increasing ghost fishing over the short term.

Utility of gillnets for selectively targeting penaeids off Iran

In response to concerns over the mortality of discards and other negative environmental impacts of otter trawling for penaeids,the utility of bottom-set gillnets deployed by artisanal vessels to target Penaeus monodon,Metapenaeus affinis and other retained species by-product was assessed in the Sea of Oman.Two gillnets(each comprising several 80-m panels for total lengths of up to 1.3 km)were diurnally fished at two locations(off Beris and Govater,eastern Iran)within established penaeid fishing grounds.During 30 days,the total catch was 2721 kg,comprising penaeids(981 kg),eight retained by-product species(598 kg and mostly Otolithes ruber,Cynoglossus bilinearus and Carangoides talamparoides)and 19 discarded species(1142 kg).The catch-per-unit-of-effort(CPUE,kg/gillnet-panel⋅hour-fished)of targeted penaeids and by-product varied significantly between areas(0.5-1.0 kg),but nevertheless reached economically viable levels.The CPUEs of total bycatch were similar at both sites(<0.5 kg)and no marine turtles were caught.The concomitant ratios of retained-catches-to-bycatch were considerably less than those for regional penaeid-trawl fisheries.Nevertheless,while gillnet selectivity was satisfactory for M.affinis,most of the P.monodon were smaller than their carapace length at maturity at both fished sites.The results support using gillnets to target penaeids and by-product species as an alternative to otter trawling in the Sea of Oman;albeit with ongoing assessments of modifications to maximise selectivity.