Estudios de marcado y recaptura de especies marinas

Los resultados obtenidos del marcado y posterior recaptura de los ejemplares son una herramienta muy valiosa para contribuir a mejorar el conocimiento de la biología y ecología de una especie, examinando ciertos aspectos como son: el crecimiento, los movimientos o migraciones, la mortalidad o supervivencia, la abundancia y distribución de la especie, el hábitat y diferenciación de poblaciones o stocks. Actualmente la técnica de marcado se aplica a muchas especies, tanto terrestres como marinas, pertenecientes a diversos grupos zoológicos: peces, crustáceos, reptiles, moluscos y mamíferos. Este libro repasa algunos ejemplos de marcado de especies marinas de interés comercial. No todas las especies pueden ser marcadas, porque es necesario cumplir una serie de requisitos para poder llevar a cabo con éxito un experimento de marcado. En uno de los apartados de esta guía, se describen los distintos aspectos a tener en cuenta para obtener buenos resultados. Se describen los principales proyectos de marcado actualmente en ejecución o en marcha llevados a cabo por el Instituto Español de Oceanografía (IEO). En primer lugar, se describe brevemente la especie, su distribución, crecimiento, reproducción, alimentación, etc. A continuación, se presenta la información del marcado, es decir, campañas realizadas, número de ejemplares marcados y algunos de los resultados obtenidos hasta la fecha a partir de las recapturas disponibles. En algunas especies, los programas de marcado se llevan realizando desde hace más de 20 años, como es el caso del atún rojo, por lo que la información disponible es bastante amplia. En otros casos por el contrario como la merluza, los proyectos son relativamente recientes, no obstante los resultados son bastante interesantes y prometedores.Nowadays many different marine animals are being tagged. This book summarizes recent tagging programs carried out by the Spanish Institute of Oceanography (IEO). Although the objectives of these various studies mainly depend on the species and each project in particular, the general aim is to better understand the biology and ecology of these animals the structure and dynamics of their populations and their capacity to respond to human activities. This book provides an overview of different aspects of this technique such as a brief history of tagging, the types of tags currently used, including both conventional and electronic tags, where and how to put them on the marine animals, some recommendations regarding how to perform a tagging survey and where to go or what to do if anyone recovers a tagged fish or marine animal. The book then summarizes the main species tagged by the IEO, making a short description of their biology followed by some of the results obtained from tagging studies undertaken until now. Other applications are to know the spatial distribution (spawning or feeding areas), estimate growth parameters, mortality and survival rates, longevity, the size of the population or identifying stocks. Nowadays the advances in electronics have also open new fields such us the possibility of tracking an animal and knowing its habitat preferences and behaviour. Besides some of these tags have the capacity of recording this information during long periods and sending the data from long distances even without the need to recover the animal. Tagging activities constitute a very useful tool to improve the knowledge of many species and contribute to their management and conservation. For that reason this methodology is included in many IEO projects in which other activities like the monitoring of the fishery (landings, fishing effort, fleet characteristics, fishing areas, biological sampling, etc.) are carried out. Some projects are related with coastal pelagic fisheries including anchovy, sardine and mackerel or oceanic pelagic fisheries like tuna and billfish species and pelagic sharks. Others are focused on benthic and demersal species such as hake, black spot seabream, anglerfish, flatfish, etc. Nevertheless not all species can be tagged, as they have to survive being caught and handled before being release. For this reason, tagging techniques may not easily be applied to some species.Versión del edito

Pore structure of thermally treated goethite (α-FeOOH)

The thermal decomposition of synthetic α-FeOOH in air has been studied by X-ray powder diffraction (XRD), IR spectroscopy, transmission electron microscopy, and nitrogen adsorption. Three stages may be differentiated during the course of the reaction: (i) 200-250°C; slit-shaped micropores of nearly equal width, about 1.4 nm, are formed along the elongated direction of the lath-shaped acicular microcrystals of the hematite products, the highest surface area is obtained on a α-FeOOH decomposed at 250°C; (ii) 300-600°C; an internal sintering occurs within the microcrystals transforming the micropores into closed spherical mesopores with the consequent significant decrease in surface area; and (iii) above 600°C; interparticle sintering takes place and no valuable porosity is detected. Particle shape effects are shown to be the reason for the differences in the IR spectra and for the nonuniform broadening of the XRD peaks observed in the hematite products.Peer Reviewe

Nanopartículas aciculares de hierro protegidas frente a la sinterización con óxido de aluminio

[EN] Acicular iron nanoparticles have been obtained by thermal reduction with hydrogen of a goethite precursor protected against sintering with Al cations, either by doping during the synthesis or by a further coating and the relation between microstructure and magnetic properties of the final Fe particles has been studied in order to evaluate the efficiency of both protecting methods. Uniform goethite and Al-doped goethite precursors were prepared by oxidation with air of FeSO4 solutions, containing Al(NO3)3 when required, previously precipitated with Na2CO3, while the Al oxide coating on the undoped goethite precursor was carried out by heterocoagulation. In both protecting methods, Al cations were mainly concentrated in the particle outer layers of the goethite precursors and the final iron. Due to this Al enrichment, the growth of iron crystals during the reduction process is minimised resulting Fe particles with improved coercivity and squareness. Nevertheless, the coating procedure seems to be more effective giving rise to the iron particles with the largest coercivity, probably due to a better preservation of the acicular morphology in this case.[ES] Se han obtenido nanopartículas aciculares de hierro por reducción térmica con hidrógeno de un precursor acicular de goetita que fue protegido frente a la sinterización por la adición de cationes Al mediante dopado durante su síntesis o por recubrimiento posterior, estudiándose la relación entre la microestructura y las propiedades magnéticas de las partículas finales de α-Fe con objeto de evaluar la eficacia de ambos métodos de protección. Los precursores uniformes de goetita y de goetita dopada con Al se prepararon por oxidación con aire de disoluciones de FeSO4 o de FeSO4 y Al(NO3)3, previamente precipitadas por la adición de Na2CO3, mientras que el recubrimiento con óxido de aluminio sobre las partículas de goetita fue llevado a cabo por un procedimiento de heterocoagulación. En ambos métodos de protección, los cationes aluminio estaban principalmente concentrados en las capas más externas de las partículas, tanto de los precursores de goetita como del hierro. Debido a este enriquecimiento en Al, se minimiza el crecimiento de los cristales de hierro durante el proceso de reducción resultando partículas de Fe con mayores valores de coercitividad y de cuadratura de la curva de histéresis. No obstante, las partículas de hierro protegidas mediante recubrimiento presentaban valores de coercitividad ligeramente mayores, probablemente debido a la mejor conservación de la morfología acicular en este caso.This work was supported by the Spanish CICYT under projects MAT2002-04001-C02 and MAT2003-01479. The fellowship of R. Pozas from the Spanish Ministerio de Ciencia y Tecnología is gratefully acknowledged.Peer reviewe

Nitrogen adsorption on synthetic ferrihydrite

Low-temperature nitrogen adsorption has been used to study the structure of two samples of ferrihydrite prepared by different methods. Results of X-ray powder diffraction and infrared spectroscopy show identical characteristics for both samples. However, transmission electron microscopy, specific surface area measurements, and qualitative assessment of porosity strongly suggest different structure.Peer Reviewe

Single-step nanoengineering of silica coated maghemite hollow spheres with tunable magnetic properties

Tunable magnetic hollow spheres of γ-Fe2O3 with a silica-enriched surface layer have been synthesized by aerosol pyrolysis of an iron ammonium citrate/TEOS solution in methanol. Careful temperature control is crucial for an optimum yield of intact spheres. The Figure shows a TEM image of a sphere, revealing the outer layer consisting mainly of silica. The material is potentially interesting for magnetic-fluid applications, e.g., in medicine.Peer Reviewe

From hollow to dense spheres: Control of dipolar interactions by tailoring the architecture in colloidal aggregates of superparamagnetic iron oxide nanocrystals

The control of dipolar interactions by fabrication of colloid aggregates of superparamagnetic iron oxide nanocrystals was studied. The direct synthesis by aerosol pyrolysis of spherical aggregates containing nanomagnets with similar crystal size was described. A comprehensive analysis of the different magnitude of the dipolar interactions was carried out with the help of a mean field model. The model allows to estimate dipolar interactions in a temperature region, within which the behavior of interacting nanomagnets was described by the interacting superparamagnetic regime (ISP).Peer Reviewe

Uniform colloidal particles in solution: Formation mechanisms

Research News: Monodisperse colloids have found a wide range of technological applications, in fields as diverse as ceramics, pigments, and catalysis. Recent work in analyzing the mechanism of formation of the particles is reviewed, and the factors influencing the size and shape of the colloids, such as the SiO2 particles shown in the Figure, are discussed.Peer Reviewe

Textural properties of hydrotalcite-like compounds [Al2Li(OH)6]+X 1 m m-. nH2O (Xm-= CO3 2-, NO3 -, Cl-)

Synthetic aluminium-lithium double hydroxides, [Al2Li(OH)6]+ X1/m m-.nH2O (where Xm-= CO3 2-, NO3 -, Cl-) have been prepared by different methods. No microporosity was observed in any sample and hydrothermally treated samples showed the lowest surface area values. A good relationship is found between crystallite size and specific surface area. An explanation of the differences in textural properties found among the samples studied is given on the basis of data obtained by X-ray powder diffraction, infrared spectroscopy, scanning electron microscopy and nitrogen adsorption techniques.Peer Reviewe

Low-temperature nucleation of rutile observed by Raman Spectroscopy during crystallization of TiO2.

The thermal evolution of amorphous TiO2 powders, consisting of spherical particles and prepared by hydrolysis of a titanium ethoxide aerosol, was studied by using Raman spectroscopy. On calcination at 350°C, the solid crystallized, giving anatase as a major phase. A small amount of rutile was also detected and attributed to small seeds localized at the particle outlayer. The nucleation of rutile at so low a temperature was ascribed to the presence of organic impurities in the powders. The transformation of anatase into rutile was clearly observed after heating at 660°C. © 1992Peer Reviewe

Vibrational study of dawsonite type compounds MAl(OH)2CO3 (M = Na, K, NH4)

Infrared and Raman spectra of polycrystalline dawsonite type compounds MAl(OH)2CO3 (M = Na, K, NH4) have been obtained between 4000 and 40 cm-1. The data are interpreted on the basis of the factor group analysis of the proposed structures (D28 2h for Na and K dawsonite and D17 2h for NH4 dawsonite). In the dawsonites, lattice vibrational modes are clearly separated from the internal at around 700 cm-1. Most of the internal (OH- and CO2- 3) modes are identified and agree well with theoretical predictions. Vibrations of the OAl unit are responsible for the main features in the 700-250 cm-1 region. © 1985.This research was supported by the Comision Asesora de Investigación Científica y Técnica (CAICYT) under Project No. 512/81.Peer Reviewe