674 research outputs found

    Fishery essentiality: A short-term decision-making method based on economic viability as a tool to understand and manage data-limited small-scale fisheries

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    Small-scale fisheries (SSFs), usually overlooked and marginalized in policy processes, play an important role in contributing to food security, nutrition, livelihoods, and local and national economies. As conventional fisheries assessment is not valid for SSFs, this study puts forward several mathematical indices to numerically qualify the state of certain SSFs. We have developed a new concept of ‘essentiality’, which measures the relative importance of certain species from an economic perspective. In the framework of fishery essentiality, SSFs boats are conceptually replaced by Artisanal Fishing Units. The time dedicated to the capture of a species, the number of units that fish it, and the economic yield obtained from the sale of the catch: Frequency, Fleet Recruiting and Income, define essentiality. We have set out an overall index of essential capacity for the whole fishery. Estimating the essentiality of a fishery allows us to comparatively characterize different fishing communities, and the data-limited SSF manager has the option of introducing management measures to change the behaviour of the fishery and move towards a situation of greater essentiality, and therefore, of greater economic viability. This in turn leads to a reduction in the pressure that is focused on a limited number of specific fishing resources. The essentiality of a fishery is a plausible alternative method of assessment and management of a fishery to the traditional evaluation methods used for industrial fisheries.Versión del editor1,58

    Estimating the costs for the airport operator and airlines of a drone-related shutdown:An application to Frankfurt International Airport

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    Commercially-acquired drones threaten airport operations due to limited knowledge of airspace safety regulations or deliberate action by drone operators. This study aims to determine whether the investment cost of a drone-defence system can be justified in relation to the financial cost of a drone-related shutdown. To that end, a case study of Frankfurt Airport is carried out with simulations of different disruptions during a peak-activity period similar to the 2018 Gatwick drone incident. With data on passenger traffic and airline schedules, we developed a passenger recovery algorithm to determine the amount of delays caused by the disruptions and the costs for the airport operator and the airlines. Results show that the investment in a drone-defence system is offset by the costs of a 48-h continued closure or several smaller closures, but since the largest share of costs is borne by the airlines, investments should be shared between both stakeholder

    Catálogo de riesgos climáticos en Canarias: amenazas y vulnerabilidad

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    In spite of the apparent climatic mildness, the frequency 2nd intensity of the adversemeteorological phenomena have serious consequences in the Canary Islands. Even so the studies on these questions are only partial. For this reason we have tried to analyse the most important climatic hazards, giving special attention to the last years. We attempt to show the climatic threats that the archipelago is exposed to and the expected maximumi thresholds in each one of the phenomena cataloguied like hazard. Moreover, we present a series of reflections concerning vulnerability. It will be seen, in spite of the importance of climate being a tourist resource, the islands are not free of more extreme atmospheric events 2nd that its vulnerability increases year after year.A pesar de la supuesta suavidad climática, los fenómenos meteorológicos adversos tienen graves consecuencias en Canarias. Aún así los estudios sobre estas cuestiones son sólo parciales. Es por ello por lo que en este trabajo se pretende analizar los riesgos climáticos más importantes haciendo especial mención a los últimos años. Se señalan las amenazas climáticas a las que está expuesto el archipiélago y se muestran los umbrales rnáximos esperados en cada uno de los fenómenos catalogados como riesgos. Asimismo, se exponen una serie de reflexiones sobre la vulnerabilidad. Como se verá, aunque el clima representa el principal atractivo turístico, las islas no están exentas de las manifestaciones atmosféricas más extremas y la vulnerabilidad aumenta año tras año

    How much dark matter is there inside early-type galaxies?

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    We study the luminous mass as a function of the dynamical mass inside the effective radius (r_e) of early-type galaxies (ETGs) to search for differences between these masses. We assume Newtonian dynamics and that any difference between these masses is due to the presence of dark matter. We use several samples of ETGs -ranging from 19 000 to 98 000 objects- from the ninth data release of the Sloan Digital Sky Survey. We perform Monte Carlo (MC) simulations of galaxy samples and compare them with real samples. The main results are: i) MC simulations show that the distribution of the dynamical vs. luminous mass depends on the mass range where the ETGs are distributed (geometric effect). This dependence is caused by selection effects and intrinsic properties of the ETGs. ii) The amount of dark matter inside r_e is approximately 7% +- 22%. iii) This amount of dark matter is lower than the minimum estimate (10%) found in the literature and four times lower than the average (30%) of literature estimates. However, if we consider the associated error, our estimate is of the order of the literature average.Comment: 24 pages, 12 figures. MNRAS accepte

    Ecosystem modeling to evaluate the ecological sustainability of small-scale fisheries: A case study from El Hierro, Canary Islands

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    This paper examines various fishery management scenarios based on the recovery of small-scale fisheries (SSF) following a submarine volcanic eruption in 2011 in El Hierro Island (Canary Islands, Spain). After this catastrophic event, the SSF composition of La Restinga fishing community was affected by socio-economic and demographic changes. The uncertainty derived from this situation provides an opportunity to evaluate the fisheries’ sustainability and advice on different management options under an ecosystem-based approach. The Ecopath with Ecosim modeling framework was used to build a model of El Hierro Island, where the versatile and traditional multispecies small-scale fleet of La Restinga operates. Our main goal is to improve traditional fisheries, based on the relevance of key local fisheries and multi-specific fishery strategies in the light of scientific knowledge. Temporal simulations for the next decade were analyzed by creating scenarios of alternative fishing effort distributions based on the fishing trends observed in El Hierro small-scale community of La Restinga after a natural hazard. The outcomes of this modeling prototype show the vulnerability of some littoral and demersal species, the resilience of migratory species, and the sustainability of SSF diversification practices. These results could develop an adaptive and co-management strategy with the local fishing community to preserve the small-scale fishing system and marine resources.En prens

    Variable Stars in Local Group Galaxies. IV. RR Lyrae stars in the central regions of the low-density galaxy Crater II

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    We present a search and analysis of variable stars in the recently discovered Crater~II dwarf galaxy. Based on BB, VV, II data collected with the Isaac Newton Telescope (FoV\sim0.44 square degrees) we detected 37 variable stars, of which 34 are bone-fide RR Lyrae stars of Crater~II (28 RRab, 4 RRc, 2 RRd). We applied the metal-independent (VV, BVB-V) Period--Wesenheit relation and derived a true distance modulus (μ\mu = 20.30±\pm0.08 mag (σ\sigma=0.16 mag). Individual metallicities for RR Lyrae stars were derived by inversion of the predicted II-band Period-Luminosity relation. We find a mean metallicity of [Fe/H]=-1.64 and a standard deviation of σ[Fe/H]\sigma_{[Fe/H]} =0.21 dex, compatible with either negligible or vanishing intrinsic metallicity dispersion. The analysis of the Colour-Magnitude Diagram reveals a stark paucity of blue horizontal branch stars, at odds with other Galactic dwarfs, and globular clusters with similar metal abundances.Comment: 14 pages, 8 figures, accepted for publications on MNRAS. Time series photometry is available in the manuscript source ta

    The High-Mass End of the Red Sequence at z~0.55 from SDSS-III/BOSS: completeness, bimodality and luminosity function

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    We have developed an analytical method based on forward-modeling techniques to characterize the high-mass end of the red sequence (RS) galaxy population at redshift z0.55z\sim0.55, from the DR10 BOSS CMASS spectroscopic sample, which comprises 600,000\sim600,000 galaxies. The method, which follows an unbinned maximum likelihood approach, allows the deconvolution of the intrinsic CMASS colour-colour-magnitude distributions from photometric errors and selection effects. This procedure requires modeling the covariance matrix for the i-band magnitude, g-r colour and r-i colour using Stripe 82 multi-epoch data. Our results indicate that the error-deconvolved intrinsic RS distribution is consistent, within the photometric uncertainties, with a single point (<0.05 mag<0.05~{\rm{mag}}) in the colour-colour plane at fixed magnitude, for a narrow redshift slice. We have computed the high-mass end (0.55Mi22^{0.55}M_i \lesssim -22) of the 0.55i^{0.55}i-band RS Luminosity Function (RS LF) in several redshift slices within the redshift range 0.52<z<0.630.52<z<0.63. In this narrow redshift range, the evolution of the RS LF is consistent, within the uncertainties in the modeling, with a passively-evolving model with Φ=(7.248±0.204)×104\Phi_* = (7.248 \pm 0.204) \times10^{-4} Mpc3^{-3} mag1^{-1}, fading at a rate of 1.5±0.41.5\pm0.4 mag per unit redshift. We report RS completeness as a function of magnitude and redshift in the CMASS sample, which will facilitate a variety of galaxy-evolution and clustering studies using BOSS. Our forward-modeling method lays the foundations for future studies using other dark-energy surveys like eBOSS or DESI, which are affected by the same type of photometric blurring/selection effects.Comment: 27 pages, 20 figures, accepted for publication in MNRA

    Interferometric inverse synthetic aperture radar experiment using an interferometric linear frequency modulated continuous wave millimetre-wave radar

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    D. Felguera-Martín,1 J.-T. González-Partida,1 P. Almorox-González,1 M. Burgos-García,1 and B.-P. Dorta-Naranjo2 1Universidad Politécnica de Madrid, Ciudad Universitaria s/n, Grupo de Microondas y Radar. Departamento de Señales, Sistemas y Radiocomunicaciones, Madrid, Spain 2Universidad de Las Palmas de Gran Canaria, Departamento de Señales y Comunicaciones, Las Palmas de Gran Canaria, Spain An interferometric linear frequency modulated continuous wave (LFMCW) millimetre-wave radar is presented, along with the results of an experiment conducted to study the feasibility of using it in a future millimetre-wave interferometric inverse synthetic aperture radar (InISAR) system. First, a description of the radar is given. Then, the signal processing chain is described, with special attention to the phase unwrapping technique. The interferometric phase is obtained by unwrapping the prominent target's phase in each antenna using a sliding frame processing technique. Cell migration issues in this method are also addressed. Simulations were carried out to illustrate and assess the processing chain and to show the effects of multipath echoes on the height measurement. In the real experiment, the range, speed and height of a moving target were tracked over consecutive inverse synthetic aperture radar (ISAR) image frames, verifying the performance of the whole system
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