Anàlisi dels descartaments efectuats per la flota d'arrossegament en el Golf de Lleó

La pesca d'arrossegament practicada al mar Mediterrani incideix sobre un rang batimètric molt ampli i afecta a nombrosos tipus de fons que presenten comunitats molt diversificades, on les espècies de peixos, crustacis, cefalòpodes, altres mol·luscs, equinoderms i d'altres macroorganismes epibentònics interaccionen entre si. D'aquí la importància de caracteritzar amb una aproximació multiespecífica els fons explotats, com la que aquí hem dut a terme, prenent en consideració no tan sols les espècies d'interès comercial sinó totes les espècies que conformen la comunitat. Els objectius concrets d'aquesta tesi estan centrats en l'estudi qualitatiu i quantitatiu dels descartaments produïts per la pesca d'arrossegament que efectua la flota espanyola en la zona del Golf de Lleó, i en aspectes relacionats a millorar la selectivitat de les xarxes emprades canviant el disseny de la malla tradicional per malla quadrada. El mostreig s'ha dut a terme a bord d'una embarcació d'arrossegament comercial, amb una freqüència setmanal, dins el període comprès entre març del 1998 i març del 2000. En total s'han analitzat 68 pesques. Totes les mostres estudiades provenen del primer vol del dia i s'han capturat a fondàries entre 50 i 500 metres. De tot el volum capturat durant l'estudi s'han identificat un total de 307 espècies pertanyent a diversos grups taxonòmics. El grup taxonòmic majoritari és el dels peixos amb 133 espècies, seguit dels crustacis, els cefalòpodes, els equinoderms i finalment el grup d'altres invertebrats. L'espècie més capturada en nombre a la pesquera del Golf de Lleó ha estat la cervellina (Leptometra phalangium) i les més capturades en biomassa han estat la sardina (Sardina pilchardus) i el lluç mediterrani (Merluccius merluccius smiridus). Pel total de la captura la fracció descartada en nombre d'individus representa el 71% mentre que la biomassa descartada és de l'ordre del 36%. La causa més important en quant a quantitat de rebuig produït és la que respon al compliment de la normativa vigent, ja sigui per les talles mínimes legals o per les captures acompanyants permeses. Els majors descartaments estacionals en termes d'abundància es donen a la primavera i l'estiu, coincidint amb l'època de reclutament de la majoria de les espècies explotades. En canvi, els descartaments estacionals en termes de biomassa són excepcionalment elevats a l'estiu i estan provocats per la captura massiva de sardina (S. pilchardus) durant aquesta època de l'any. El rebuig expressat tant en nombre com en pes disminueix en funció de l'estrat de fondària, essent la quantitat descartada major en l'estrat A (50-200 m) i menor en l'estrat C (>400 m). S'ha comprovat que el disseny de malla quadrada aplicat al cóp de les xarxes d'arrossegament fa augmentar dràsticament, tant en nombre com en pes, el percentatge d'individus escapats, disminuint a la vegada la quantitat de descartament. També s'aconsegueix un augment de la mida de primera captura (L50) de totes les espècies excepte en la bruixa de quatre taques (Lepidorhombus boscii). A més es redueix l'impacte de la pesca sobre els estocs d'individus juvenils, sobretot d'espècies que presenten una secció de cos rodona com el lluç mediterrani (M. merluccius smiridus) i el verat (Scomber scombrus), disminuint així la sobrepesca de creixement i de reclutament al mateix temps que s'assegura i es millora la venda d'exemplars de mida legal.

Distribució espacial i ús de l'hàbitat de la comunitat de peixos a l'estany de Banyoles

En el marc d'un projecte més ampli sobre la comunitat de peixos de la conca lacustre de Banyoles, s'ha estudiat la distribució espacial de les diferents espècies així com l'ús que aquestes fan de l'hàbitat. El poblament piscícola de l'estany de Banyoles és el resultat d'un llarg historial d'introducció d'espècies exòtiques i extinció de les poblacions autòctones locals. S'ha revisat la seva composició actual detectant un total de 18 espècies (4 autòctones i 14 introduïdes) de les quals només 13 presenten una població estable. L'estudi de l'hàbitat s'ha centrat a l'Estany, l'element principal del sistema lacustre, analitzant per separat la zona litoral i la zona limnètica. En el primer cas s'han realitzat les captures d'individus mitjançant pesca elèctrica des d'una embarcació adaptada per aquesta pràctica. La totalitat del litoral ha estat dividida en trams de característiques homogènies on s'han obtingut les captures per unitat d'esforç per cada espècie. El mostreig s'ha desenvolupat entre l'estiu de 1997 i la primavera del 2000 realitzant un total de 10 campanyes de pesca. Les espècies més abundants al litoral són la perca americana (Micropterus salmoides) i el peix sol (Lepomis gibbosus), essent també presents la perca (Perca fluviatilis), carpa (Cyprinus carpio) i el gardí (Scardinius erythrophthalmus). S'han capturat altres espècies com ara anguila (Anguilla anguilla), bagra (Squalius cephalus), sandra (Sander lucioperca), carpí (Carassius auratus) i madrilleta vera (Rutilus rutilus), però són molt menys abundants en nombre. S'ha examinat, per cadascuna de les espècies, si existeix selecció de l'hàbitat i en cas afirmatiu, quin és el preferent en base a la classificació del litoral en sis tipus de vegetació predominant. Les espècies més abundants, perca americana i peix sol, ocupen tots els hàbitats disponibles però amb una densitat diferent. La perca mostra també una clara selecció de l'hàbitat a favor de les zones molt estructurades amb abundant presència de jonca litoral. Carpa i gardí seleccionen els ambients més fondos amb major presència de matèria orgànica d'origen vegetal procedent del bogar. En general els individus ocupen les zones amb una densitat de vegetació intermèdia, majoritàriament zones de jonca a l'estiu i zones amb mansega a l'hivern, on troben refugi i els recursos tròfics necessaris. La perca americana, a més, presenta una elevada fidelitat a un mateix punt del litoral al llarg de la seva vida. La zona limnètica ha estat prospectada mensualment mitjançant ecosondació, realitzant transectes perpendiculars a l'eix principal de l'Estany, cobrint la seva totalitat. La composició d'espècies s'ha obtingut a partir de les captures fetes amb xarxes (tresmalls) amb periodicitat estacional. L'anàlisi geoestadística de la densitat de peixos ha permès descriure l'estructura espacial d'aquesta a partir dels variogrames, així com la seva variabilitat tant espacial com temporal, i obtenir els mapes de densitat. A l'hivern, la densitat de peixos a la zona limnètica assoleix els seus valors mínims i els individus es troben formant agregats dispersos, pels diferents estrats de fondària. A partir de la primavera la densitat augmenta, pel reclutament i la major freqüència d'individus que abandonen el litoral; la densitat esdevé més homogènia a les primer capes de fondària. A l'estiu la densitat és màxima i l'estrat més homogeni coincideix amb la posició de la termoclina. Aquest estructura varia en disminuir la temperatura i barrejar-se la columna d'aigua, tornant a la situació hivernal. La perca i la madrilleta vera són les espècies predominants en aquest ambient, juntament amb la carpa. La seva distribució no és homogènia i respon a les característiques limnològiques de les diferents cubetes de l'Estany. Una particularitat d'aquest, relacionada amb el seu origen càrstic, es la formació d'una ploma hidrotermal que afecta la distribució dels peixos, probablement en augmentar la terbolesa. S'ha integrat l'ús de l'hàbitat de les espècies que ocupen tant la zona limnètica com la litoral a partir del seguiment d'individus, concretament de perca i bagra. S'ha utilitzat un sistema automàtic de posicionament que estima la localització dels individus marcats amb transmissor de telemetria acústica. L'anàlisi dels desplaçaments mostra un rang superior per la bagra en comparació amb la perca. Ambdues espècies mostren una orientació en els seus desplaçaments. La perca ocupa el litoral a la nit i es desplaça a la zona limnètica de dia, amb un ritme d'activitat marcat per dos màxims coincidint amb la sortida i posta de sol; en canvi la bagra mostra una major activitat nocturna amb zones de repòs properes al litoral. S'ha estimat igualment els dominis vital de cada individu marcat.

Seston capture by Hydropsyche siltalai and the accuracy of capture efficiency estimates

1. Suspension feeding by caseless caddisfly larvae (Trichoptera) constitutes a major pathway for energy flow, and strongly influences productivity, in streams and rivers. 2. Consideration of the impact of these animals on lotic ecosystems has been strongly influenced by a single study investigating the efficiency of particle capture of nets built by one species of hydropsychid caddisfly. 3. Using water sampling techniques at appropriate spatial scales, and taking greater consideration of local hydrodynamics than previously, we examined the size-frequency distribution of particles captured by the nets of Hydropsyche siltalai. Our results confirm that capture nets are selective in terms of particle size, and in addition suggest that this selectivity is for particles likely to provide the most energy. 4. By incorporating estimates of flow diversion around the nets of caseless caddisfly larvae, we show that capture efficiency (CE) is considerably higher than previously estimated, and conclude that more consideration of local hydrodynamics is needed to evaluate the efficiency of particle capture. 5. We use our results to postulate a mechanistic explanation for a recent example of interspecific facilitation, whereby a reduction of near-bed velocities seen in single species monocultures leads to increased capture rates and local depletion of seston within the region of reduced velocity.

Physical properties of Hydropsyche siltalai (Trichoptera) net silk

Most suspension-feeding trichopterans spin a fine-silk capture net that is used to remove suspended matter from the water. The efficiency of these nets has previously been studied by considering the geometry of the web structure but the material from which the nets is constructed has received little attention. We report measurements of the tensile strength and extensibility of net silk from Hydropsyche siltalai. These measurements place caddisfly silk as one of the weakest natural silks so far reported, with a mean tensile strength of 221 +/- 22 megaNewtons (MN)/m(2). We also show that H. siltalai silk can more than double in length before catastrophic breakage, and that the silk is at least 2 orders of magnitude stronger than the maximum force estimated to act upon it in situ. Possible reasons for this disparity include constraints of evolutionary history and safety margins to prevent net failure or performance reduction.

Seasonal 'fall out' of sessile macro-fauna from submarine cliffs: quantification, causes and implications

Submarine cliffs are typically crowded with sessile organisms, most of which are ultimately exported downwards. Here we report a 24 month study of benthic fauna dropping from such cliffs at sites of differing cliff angle and flow rates at Lough Hyne Marine Nature Reserve, Co. Cork, Ireland. The magnitude of 'fall out' material collected in capture nets was highly seasonal and composed of sessile and mobile elements. Sponges, ascidians, cnidarians, polychaetes, bryozoans and barnacles dominated the sessile forms. The remainder (mobile fauna) were scavengers and predators such as asteroid echinoderms, gastropod molluscs and malacostracan crustaceans. These were probably migrants targeting fallen sessile organisms. 'Fall out' material (including mobile forms) increased between May and August in both years. This increase in 'fall out' material was correlated with wrasse abundance at the cliffs (with a one month lag period). The activities of the wrasse on the cliffs (feeding, nest building and territory defence) were considered responsible for the majority of 'fall out' material, with natural mortality and the activity of other large mobile organisms (e.g. crustaceans) also being triplicated. Current flow rate and cliff profile were important in amount of 'fall out' material collected. In low current situations export of fallen material was vertical, while both horizontal and vertical export was associated with moderate to high current environments. Higher 'fall out' was associated with overhanging than vertical cliff surfaces. The 'fall out' of marine organisms in low current situations is likely to provide ail important source of nutrition in close proximity to the cliff, in an otherwise impoverished soft sediment habitat. However, in high current areas material will be exported some distance from the source, with final settlement again occurring in soft sediment habitats (as current speed decreases).

2D parallel interpenetration of [M-2(bpp)(4)X-4] [M, Fe(II)/Co(II); bpp, 4,4 '-trimethylenedipyridine; X, SCN-SeCN- and N-3(-)] complexes: pseudohalide-dependent conformation of bpp

Three coordination complexes of Co(II)/Fe(II) with 4,4'-trimethylenedipyridine (bpp) and pseudohalides (SCN-, SeCN- and N-3(-)) have been synthesized. The complexes have been characterized by X-ray single crystal structure determination. They are isomorphous having 2D layers in which two independent wavy nets display parallel interwoven structures. Pseudohalide binds metal centers through N terminal and occupies the trans axial positions of the octahedral metal coordination environment. Pseudohalide remains pendant on both sides of the polymeric layer and help the stacking through hydrogen bonding. The conformation of bpp in the interpenetrated nets is observed to be dependent on the choice of pseudohalide. (C) 2008 Elsevier Inc. All rights reserved.

New copper(I) cyanide networks: interpenetration, self-penetration and polymorphism

The structures Of four alkali-metal copper (I) cyanides, KCu2(CN)(3)(H2O)-H-.-II (I), K2Cu3(CN)(5) (II), CsCu3(CN)(4) (III) and KCu3(CN)(4) (IV) are described. Three of these, ((II)-(IV)), with previously unknown ACN:CuCN ratios have new copper-cyanide frameworks, whilst (1) is a new polymorph of KCu2(CN)(3)(H2O)-H-.. These structures are discussed in terms of assembly from the simple building units Cu(CN)(2/2), Cu(CN)(3/2), Cu(CN)(2/2)(CN)(1/1) and Cu(CN)(4/2). Compounds (I), (II) and (III) are layered materials based on (6,3) nets containing (CuCN)(6) rings (I) and (CuCN)(8) rings (II) and (III). In compound (IV), (4,4) nets containing (CuCN)(12) rings link to generate a three-dimensional network. Both (III) and (IV) are examples of interpenetrating solids in which two and four identical networks interweave, respectively. These materials illustrate the structural versatility of copper (I) in cyanide frameworks. (c) 2006 Elsevier SAS. All rights reserved.

The SAFEE on-board threat detection system

Under the framework of the European Union Funded SAFEE project(1), this paper gives an overview of a novel monitoring and scene analysis system developed for use onboard aircraft in spatially constrained environments. The techniques discussed herein aim to warn on-board crew about pre-determined indicators of threat intent (such as running or shouting in the cabin), as elicited from industry and security experts. The subject matter experts believe that activities such as these are strong indicators of the beginnings of undesirable chains of events or scenarios, which should not be allowed to develop aboard aircraft. This project aimes to detect these scenarios and provide advice to the crew. These events may involve unruly passengers or be indicative of the precursors to terrorist threats. With a state of the art tracking system using homography intersections of motion images, and probability based Petri nets for scene understanding, the SAFEE behavioural analysis system automatically assesses the output from multiple intelligent sensors, and creates. recommendations that are presented to the crew using an integrated airborn user interface. Evaluation of the system is conducted within a full size aircraft mockup, and experimental results are presented, showing that the SAFEE system is well suited to monitoring people in confined environments, and that meaningful and instructive output regarding human actions can be derived from the sensor network within the cabin.

Synapsing variable length crossover: Biologically inspired crossover for variable length genomes

Biological Crossover occurs during the early stages of meiosis. During this process the chromosomes undergoing crossover are synapsed together at a number of homogenous sequence sections, it is within such synapsed sections that crossover occurs. The SVLC (Synapsing Variable Length Crossover) Algorithm recurrently synapses homogenous genetic sequences together in order of length. The genomes are considered to be flexible with crossover only being permitted within the synapsed sections. Consequently, common sequences are automatically preserved with only the genetic differences being exchanged, independent of the length of such differences. In addition to providing a rationale for variable length crossover it also provides a genotypic similarity metric for variable length genomes enabling standard niche formation techniques to be utilised. In a simple variable length test problem the SVLC algorithm outperforms current variable length crossover techniques.

A grouped P2P network for scalable grid information services

Information services play a crucial role in grid environments in that the state information can be used to facilitate the discovery of resources and the services available to meet user requirements, and also to help tune the performance of a grid system. However, the large size and dynamic nature of the grid brings forth a number of challenges for information services. This paper presents PIndex, a grouped peer-to-peer network that can be used for scalable grid information services. PIndex builds on Globus MDS4, but introduces peer groups to dynamically split the large grid information search space into many small sections to enhance its scalability and resilience. PIndex is subsequently modeled with Colored Petri Nets for performance evaluation. The simulation results show that PIndex is scalable and resilient in dealing with a large number of peer nodes.

Simple adaptive momentum: new algorithm for training multilayer perceptrons

The speed of convergence while training is an important consideration in the use of neural nets. The authors outline a new training algorithm which reduces both the number of iterations and training time required for convergence of multilayer perceptrons, compared to standard back-propagation and conjugate gradient descent algorithms.

Chaucer's presence in songes and sonettes

In an elegy to Wyatt published in Tottel’s Miscellany, Surrey claims that Wyatt ‘reft Chaucer the glory of his wit’. This statement, which both lauds and resists Chaucer, is a microcosm of the way Chaucer is treated throughout the Miscellany. In examining the collection’s paradoxical attitude to Chaucer, this essay focuses particularly on the Squire’s Tale, the Franklin’s Tale, Anelida and Arcite, the Legend of Good Women, and several short lyrics. In its interest in courtly love poetry and Petrarch, the Miscellany follows a trajectory in English poetry set by Chaucer. Its courtly verse is saturated with words, phrases, and tropes from his poetry. Rhyme royal, which he introduced into English poetry, is widely used. The Canterbury Tales has been fully assimilated and can be referred to allusively with the same confidence of the audience’s knowledge as is the case when referring to classical myth; in Wyatt’s ‘Myne owne Jhon Poins’, the speaker, disclaiming deceitfulness, says that he cannot ‘say that Pan/ Passeth Appollo in musike manifold:/ Praise syr Topas for a noble tale,/ And scorne the story that the knight tolde’ (lines 48-50). However, Chaucer’s poetry is also downplayed and contested in the Miscellany. ‘Truth’, the only poem of his which appears in the volume, is disingenuously placed in the ‘Uncertain Authors’ section. In addition, some of the most important elements of his work are strongly resisted in the Miscellany, either ignored, dismissed or challenged. These elements include Chaucer’s interest in variety of voice, his sympathetic engagement with women, particularly wronged women, and his interest in female speech and particularly female complaint. The Miscellany, by contrast, is dominated by male-voiced lyrics preoccupied with the pain inflicted on the lover by a lady who is frequently unfeeling, cruel, or faithless. Chaucer’s frequent focus on the cynical seduction and betrayal of female by male is reversed in the Miscellany, and the language and metaphors he uses to express male cruelty (e.g. the word ‘newfangleness’ and images of hooks, nets and traps) are usurped to describe the lady’s cruelty to the suffering lover. On occasion, poems in the Miscellany challenge specific Chaucerian texts; ‘On His Love Named White’ throws down a gauntlet to The Book of the Duchess, while two of Surrey’s poems implicitly take issue with the female falcon’s voice in the Squire’s Tale, giving the deceitful tercelet the opportunity to shout down the falcon’s charges. The essay thus shows that in many respects Tottel’s Miscellany is only superficially Chaucerian, and that it both passively and actively takes issue with Chaucer’s work.

Foreword: International Space Science Institute (ISSI) workshop on the Earth’s cryosphere and sea level change

Rising sea level is perhaps the most severe consequence of climate warming, as much of the world’s population and infrastructure is located near current sea level (Lemke et al. 2007). A major rise of a metre or more would cause serious problems. Such possibilities have been suggested by Hansen and Sato (2011) who pointed out that sea level was several metres higher than now during the Holsteinian and Eemian interglacials (about 250,000 and 120,000 years ago, respectively), even though the global temperature was then only slightly higher than it is nowadays. It is consequently of the utmost importance to determine whether such a sea level rise could occur and, if so, how fast it might happen. Sea level undergoes considerable changes due to natural processes such as the wind, ocean currents and tidal motions. On longer time scales, the sea level is influenced by steric effects (sea water expansion caused by temperature and salinity changes of the ocean) and by eustatic effects caused by changes in ocean mass. Changes in the Earth’s cryosphere, such as the retreat or expansion of glaciers and land ice areas, have been the dominant cause of sea level change during the Earth’s recent history. During the glacial cycles of the last million years, the sea level varied by a large amount, of the order of 100 m. If the Earth’s cryosphere were to disappear completely, the sea level would rise by some 65 m. The scientific papers in the present volume address the different aspects of the Earth’s cryosphere and how the different changes in the cryosphere affect sea level change. It represents the outcome of the first workshop held within the new ISSI Earth Science Programme. The workshop took place from 22 to 26 March, 2010, in Bern, Switzerland, with the objective of providing an in-depth insight into the future of mountain glaciers and the large land ice areas of Antarctica and Greenland, which are exposed to natural and anthropogenic climate influences, and their effects on sea level change. The participants of the workshop are experts in different fields including meteorology, climatology, oceanography, glaciology and geodesy; they use advanced space-based observational studies and state-of-the-art numerical modelling.