Reasons for the decline of Acipenser sturio L., 1758 in central Europe, and attempts at its restoration

Los esturiones están siendo crecientemente amenazados en todo el mundo por la explotación comercial y la presión ambiental. Una especie que anticipó lo ocurrido con las restantes especies de esturiones es Acipenser sturio L., 1758. Desde finales del siglo XIX, los mermados stocks han causado grave preocupación respecto a la supervivencia de la especie. Se han intentado diversas medidas de gestión, pero debido a las presiones económicas y políticas, así como al muy limitado conocimiento de la biología de la especie, raramente las medidas tomadas han sido de protección efectiva. En muchos países, los conservacionistas y biólogos pesqueros han perdido la esperanza de salvar a la especie de la extinción después de haber fracasado los primeros intentos de reproducción artificial y repoblación. Adicionalmente, la protección y la conservación de la especie, hasta la década de los noventa, se acometían sólo a escala nacional. Bajo estas condiciones, los investigadores franceses han constituido un ejemplo, con un programa de recuperación a largo plazo que también trata de llenar los vacíos de conocimiento en muchos campos de la biología. Hasta la mitad de los noventa, ésta fue la única perspectiva para la protección de la especie y salvarla de la extinción. Recientemente, la restauración y la conservación de A. sturio han recibido creciente atención en varios países. Se discuten los factores de impacto para su declive, a partir de los datos de los ríos centroeuropeos, así como su relevancia para la restauración. Se resumen los intentos nacionales e internacionales para proteger a la especie y se presentan la evaluación de su eficacia y un bosquejo de las potenciales alternativas.Sturgeons are becoming increasingly threatened world-wide by commercial exploitation and environmental stress. A species that anticipated the development of the remaining sturgeon species is Acipenser sturio L., 1758. Since the end of the last century, diminishing stocks have caused severe concern with regard to the survival of the species. Several attempts at management measures have been suggested, but due to economic and political pressure, as well as to very limited knowledge on the biology of the species, rarely have any effective protection measures been taken. Conservationists and fisheries biologists in many countries had given up hope of saving the species from extinction after early attempts at artificial reproduction and restocking had failed. Additionally, protection and conservation of the species, until the 1990s, was at the national level only. Under these conditions, French researchers have set an example with a long-term recovery programme that also tries to close the gaps of knowledge in many fields of biology. Until the mid-1990s this was the only active approach to protect and save the species from extinction. Recently, the restoration and conservation of A. sturio have received increased attention in several countries. The impacting factors upon the decline, based on the data from Central European rivers, as well as their relevance for restoration, are discussed. The national and international attempts to protect the species are summarised. The evaluation of their efficiency and an outline of potential alternatives are also presented.Instituto Español de Oceanografí

Re-establishment programme for Acipenser sturio L., 1758: The German approach

Acipenser sturio L., 1758 was a prevalent species of the fish communities in all major German rivers' waters until the end of the 19th century. Since then, the population sizes decreased rapidly due to overfishing, pollution, and hydro-construction, and the last remaining population was observed in the Eider River until the 1960s. Recently, specimens have been observed in German waters only rarely. Until the end of the 1980s, neither politicians nor ecologists considered reestablishment measures feasible in Germany. In 1994, joint activities of scientists and aquaculturists led to the foundation of the Society to Save the Sturgeon (A. sturio L.), aimed at co-ordinating the A. sturio restoration measures in Germany. A federal programme was initiated, supporting in part the various subprojects dealing with this matter. Under a scientific co-operation agreement with France's Cemagref, the Institute of Freshwater Ecology and Inland Fisheries (IGB) in Berlin received, in May 1996, juvenile A. sturio for the establishment of a broodstock, as an ex-situ measure to save the species. The IGB also carries out research on various aspects of A. sturio biology. Together with the Cemagref, genetic analyses of remaining populations and specimens are conducted as a basis for a long-term breeding programme. The broodstock development is carried out in co-operation with the Research Institute for Agriculture and Fisheries of Mecklenburg-Vorpommern, where experiments with model species are performed within the framework of the programme. Evaluation measures for the restoration of A. sturio in the Odra and Elbe Rivers are carried out by the Society in collaboration with the Institute for Inland Fisheries of Poland. Additionally morphometric and meristic studies are conducted at the University of Rostock to characterise the species. The evaluation of the remaining populations in other European regions, in particular Romania and Georgia, is considered an important element for its future development. International co-operation in general is an essential aspect of future attempts to save the species.Acipenser sturio L., 1758 fue una especie frecuente en las comunidades de peces en las aguas de todos los grandes ríos alemanes hasta finales del siglo XIX. Desde entonces, los tamaños de las poblaciones disminuyeron rápidamente debido a sobrepesca, contaminación y obras hidráulicas, y la última población superviviente fue observada en el río Eider hasta la década de los sesenta. Recientemente, sólo raramente han sido observados ejemplares en aguas alemanas. Hasta finales de los ochenta, ni políticos ni ecologistas consideraron posibles las medidas de recuperación en Alemania. En 1994 las actividades conjuntas de científicos y acuicultores llevaron a la fundación de la Sociedad para Salvar el Esturión (A. sturio L.), aspirante a coordinar las medidas de recuperación de A. sturio en ese país. Se inició un programa federal, financiando en parte distintos subproyectos. Bajo un acuerdo científico de cooperación con Cemagref de Francia, el Instituto de Ecología Dulceacuícola y Pescas Interiores (IGB) de Berlín recibió, en mayo de 1996, juveniles de A. sturio para el establecimiento de un stock de cría, como una medida ex-situ para salvar a la especie. El IGB también investiga sobre varios aspectos de la biología de A. sturio; colabora con Cemagref en la realización de análisis genéticos de las poblaciones y de ejemplares remanentes como base para un programa de cría a largo plazo. El desarrollo del stock de cría se lleva a cabo en cooperación con el Instituto de Investigación para Agricultura y Pesca de Mecklenburg-Vorpommern, donde se realizan estudios experimentales con especies modelo dentro del marco del programa. Las medidas de evaluación para la recuperación de A. sturio en los ríos Oder y Elba se establecen por la Sociedad para Salvar el Esturión en colaboración con el Instituto de Pescas Interiores de Polonia. Adicionalmente se llevan a cabo estudios morfométricos y merísticos en la Universidad de Rostock para caracterizar a la especie. La evaluación de las poblaciones remanentes en otras regiones europeas, particularmente en Rumania y Georgia, se considera un elemento importante para su futuro desarrollo. La cooperación internacional en general es un aspecto esencial de los intentos futuros para salvar a la especie.Instituto Español de Oceanografí

Sturgeon spawning grounds in the Odra River tributaries: A first assessment

As part of a feasibility study for the re-establishment of Acipenser sturio L., 1758 in its previous range in German and Polish waters, a habitat assessment was initiated for the Odra River watershed. Spawning habitat for sturgeons is considered to be of major importance for the successful restoration and subsequent reproduction of the species, since it supports the most vulnerable life stages. The ongoing restoration project comprises three distinct phases; the first phase included the evaluation of readily available habitat. Habitat requirements were identified based on published information on sturgeon reproduction, historical catch data, and early life history. Potential spawning habitats were determined in a first step based on historic records. For the identified historic spawning sites, recent data on migration obstacles and water pollution were evaluated, thus excluding non-accessible or adversely affected sites. In the Drawa River -described as a sturgeon spawning habitat until 1939- potentially suitable habitats were determined to be readily available. Data were gathered on the dynamic of the discharge, water quality, longitudinal profiles and cross-sections of the river, as well as substrate composition. Five river stretches comprising approximately 15 000 m³ were identified as being potentially suitable for sturgeon spawning. Assuming an average fertility of 1 million eggs per female and a maximum density of 3 500 eggs/m³, the spawning-site surface required for an average female would comprise approximately 350 m³. Thus, the Drawa River could provide a spawning habitat for approx. 50 females.Como parte de un estudio de viabilidad para el restablecimiento de Acipenser sturio L., 1758 en su distribución original en aguas alemanas y polacas, se inició una valoración del hábitat en la cuenca del río Oder. Se considera que el hábitat de freza para los esturiones es de mayor importancia para el éxito de la recuperación y subsecuente reproducción de las especies, ya que mantiene los estados vitales más vulnerables. El proyecto de recuperación en marcha comprende tres fases diferentes; la primera incluyó la evaluación de hábitat fácilmente disponible. Los requerimientos de hábitat fueron identificados a partir de información publicada sobre la reproducción del esturión, datos históricos de capturas, e historia natural temprana. Los hábitats potenciales de freza fueron determinados, en una primera fase, a partir de citas históricas. Para los lugares de freza históricos identificados, los datos recientes sobre obstáculos a la migración y contaminación del agua fueron evaluados, excluyendo los lugares no accesibles o adversamente afectados. En el río Drawa -descrito como un hábitat de freza para el esturión hasta 1939- los hábitats potencialmente apropiados fueron determinados para ser fácilmente disponibles. Se reunieron datos sobre dinámica de la descarga, calidad del agua, perfiles longitudinales y secciones transversales del río, así como de la composición del sustrato. Cinco secciones fluviales, comprendiendo aproximadamente 15 000 m³, fueron identificadas como potencialmente apropiadas para la freza del esturión. Asumiendo una fecundidad media de un millón de huevos por hembra y una densidad máxima de 3 500 huevos/m³, la superficie de lugar de freza requerida para una hembra media comprendería aproximadamente 350 m³. Así, el río Drawa podría proporcionar un hábitat de freza para aproximadamente 50 hembras.Instituto Español de Oceanografí

Restoration of Acipenser sturio L., 1758 in Germany: Growth characteristics of juvenile fish reared under experimental indoor conditions

The survival of the highly endangered Acipenser sturio L., 1758 depends nearly exclusively upon the establishment of captive broodstocks. Such measures were initiated in Germany in 1996, due to a transfer of 40 artificially reproduced individuals from France under a co-operation agreement. We report the results of rearing these fish for a period of 3 years under freshwater conditions. During the first year the fish being exclusively fed frozen chironomid larvae (N = 40) grew from a median of 27 cm (with range of 23-31 cm), averaging 71 g (42-112 g), to 43 cm (38-51 cm) and 280 g (168-505 g) at a mean temperature of 20 °C (13-27 °C). Following their transfer to larger tanks (approx. 5 m³) at a mean temperature of 21 °C (17-24 °C), the fish (N = 27) reached a length of 68 cm (56-76 cm), averaging 1 281 g (512-2 097 g) at the end of the second year. Decreasing growth and increasing food conversion rates (FCR) during the first four months of the third year made us change the food composition (addition of large chironomids, krill and small marine fish). An increase in growth and a decrease in FCR was observed over the next four months resulting in a median length of 76 cm (58-89 cm), with a weight of 1 827 g (855-3 462 g) at the end of the third year (N = 27). Our fish showed rather large differences in growth, with some individuals reaching the maximum weight gain observed in wild fish, thus indicating the potential to optimise results by future testing involving additional natural food items in order to develop a formulated diet to stimulate early sexual maturation.La supervivencia del altamente amenazado Acipenser sturio L., 1758 depende casi exclusivamente del establecimiento de stocks de cría en cautividad. Tales medidas fueron iniciadas en Alemania en 1996, gracias a la transferencia desde Francia bajo un convenio de cooperación de 40 individuos reproducidos artificialmente. Presentamos los resultados de la cría de estos peces por un periodo de tres años en condiciones dulceacuícolas. Durante el primer año los peces (N = 40) siendo alimentados exclusivamente con larvas congeladas de quironómidos crecieron desde una media de 27 cm (con rango de 23-31 cm), promediando 71 g (42-112 g), a 43 cm (38-51) y 280 g (168-505 g) a una temperatura media de 20 °C (13-27 °C). A continuación de su traslado a tanques más grandes (de aproximadamente 5 m³) a una temperatura media de 21 °C (17-24 °C), los peces (N = 27) alcanzaron una longitud de 68 cm (56-76 cm), promediando 1 281 g (521-2 097 g) al final del segundo año. La disminución del crecimiento y el incremento de las tasas de con versión de alimento (TCA) durante los primeros cuatro meses del tercer año nos hicieron cambiar la composición del alimento (adición de quironómidos de gran tamaño, krill y pequeños peces marinos). Un incremento en el crecimiento y una disminución de las TCA fueron observados durante los cuatro meses siguientes resultando una longitud media de 76 cm (58-89 cm), con un peso de 1 827 g (855-3 462 g) al final del tercer año (N = 27). Nuestros peces mostraron numerosas diferencias en crecimiento, con algunos individuos alcanzando la mayor ganancia en peso observada en peces silvestres, indicando así el potencial para optimizar resultados por futuras pruebas que incluyan alimentos naturales adicionales en orden a evaluar una dieta formulada para estimular la maduración sexual temprana.Instituto Español de Oceanografí

Up-regulation of endoplasmic reticulum stress induced genes of the unfolded protein response in the liver of periparturient dairy cows

BACKGROUND: In dairy cows, the periparturient phase is a stressful period, which is commonly associated with strong metabolic adaptations and the development of pathophysiologic conditions and disorders. Some of the symptoms occurring in the liver, such as the development of fatty liver, are similar to those observed under the condition of endoplasmic reticulum (ER) stress. Therefore, we hypothesized, that in the liver of dairy cows ER stress is induced during the periparturient phase, which in turn leads to an induction of the unfolded protein response (UPR). In order to investigate this hypothesis, we determined relative mRNA concentrations of 14 genes of the ER stress-induced UPR in liver biopsy samples of 13 dairy cows at 3 wk antepartum and 1, 5 and 14 wk postpartum. RESULTS: We found, that the mRNA concentrations of 13 out of the 14 genes involved in the UPR in the liver were significantly increased (1.9 to 4.0 fold) at 1 wk postpartum compared to 3 wk antepartum. From 1 wk postpartum to later lactation, mRNA concentrations of all the genes considered were declining. Moreover, at 1 wk postpartum, mRNA concentration of the spliced variant of XBP1 was increased in comparison to 3 wk antepartum, indicating that splicing of XBP1 – a hallmark of ER stress - was induced following the onset of lactation. CONCLUSION: The present study reveals, that ER stress might be induced during the periparturient phase in the liver of dairy cows. We assume that the ER stress-induced UPR might contribute to the pathophysiologic conditions commonly observed in the liver of periparturient cows, such as the development of fatty liver, ketosis or inflammation

Positron Acceleration in Plasma Wakefields

Plasma acceleration has emerged as a promising technology for future particle accelerators, particularly linear colliders. Significant progress has been made in recent decades toward high-efficiency and high-quality acceleration of electrons in plasmas. However, this progress does not generalize to acceleration of positrons, as plasmas are inherently charge asymmetric. Here, we present a comprehensive review of historical and current efforts to accelerate positrons using plasma wakefields. Proposed schemes that aim to increase the energy efficiency and beam quality are summarised and quantitatively compared. A dimensionless metric that scales with the luminosity-per-beam power is introduced, indicating that positron-acceleration schemes are currently below the ultimate requirement for colliders. The primary issue is electron motion; the high mobility of plasma electrons compared to plasma ions, which leads to non-uniform accelerating and focusing fields that degrade the beam quality of the positron bunch, particularly for high efficiency acceleration. Finally, we discuss possible mitigation strategies and directions for future research.Comment: 24 pages (30 pages with references), 22 figure

Betatron radiation diagnostics for AWAKE Run 2

AWAKE Run 2 aims to preserve the transverse normalised emittance of an externally injected electron beam throughout acceleration, requiring a new diagnostic to measure the beam emittance after the accelerating plasma stage. Spectroscopy of the betatron emission from the electron beam could be suitable for this case. The method of trace-space reconstruction from a measured betatron spectrum is described via a simplified analytical model in order to assess its suitability the AWAKE experiment. The expected betatron emission from witness electrons at AWAKE is characterised using 3D quasi-static PIC simulations, revealing a measurable quantity of UV to soft x-ray emission. Practical challenges for the measurement are discussed