Site fidelity and movements of gilthead sea bream (Sparus aurata) in a coastal lagoon (Ria Formosa, Portugal)     

David Abecasis  Karim Erzini 《Estuarine, Coastal and Shelf Science》2008,79(4):758-763

Short-time site fidelity and movements of gilthead sea bream (Sparus aurata) in a coastal lagoon were determined using passive acoustic telemetry. Nine fish, ranging from 20.1 to 32.5 cm total length, were surgically implanted with acoustic transmitters and monitored for up to 179 days. Minimum convex polygon areas ranged from 18,698.6 m² to 352,711.9 m². Home range sizes were small, with individuals using core areas on a daily basis. However, these core areas shifted within the study site over time towards the opening to the sea. Two different diel behaviors were recorded, with some individuals more active at night and others during day time. Some individuals also demonstrated homing abilities, returning to the capture site after being released more than 4 km away.  相似文献   

Challenges facing a network of representative marine protected areas in the Mediterranean: prioritizing the protection of underrepresented habitats     

Abdulla  Ameer; Gomei  Marina; Hyrenbach  David; Notarbartolo-di-Sciara  Giuseppe; Agardy  Tundi 《ICES Journal of Marine Science》2009,66(1):22-28

  相似文献   

Spatial Variability of Mass Movements in the Satluj Valley,Himachal Pradesh during 1990～2006     

Vikram Gupta  M. P. Sah 《山地科学学报》2008,5(1):38-51

Satluj Valley is known to have a history of landslides and related mass movement activities since the geological times. Geological and geomorphological settings combined with anthropogenic activities constitute a propensity towards slope failure. During the last two decades,the area witnessed substantial increase in athropogenic pressure,mainly due to the exploitation of hydropower potential,changing landuse pattern and population growth. In addition,a shift of the climatic patterns in the form of larger area falling under the influence of rains was observed. These natural as well as anthropogenic changes in the area have resulted in increased spatial coverage of landslide in the area. This paper documents these changes during 1990～2006.  相似文献   

RFI Test Observations at a Candidate Ska Site in China     

B. Peng  J. M. Sun  H. Y. Zhang  T. Y. Piao  J. Q. Li  L. Lei  T. Luo  D. H. Li  Y. J. Zheng  R. NAN 《Experimental Astronomy》2004,17(1-3):423-430

Radio frequency interference (RFI) test observations were carried out at one of the candidate Square Kilometre Array (SKA) sites in Guizhou province, following the “RFI Measurement Protocol for Candidate SKA Sites” (hereafter RFI protocol). All data (raw and calibrated) are preserved in some suitable format, such as that set by the international RFI working group of the Site Evaluation and Selection Committee (SESC). An RFI test in December 2003 was performed according to Mode 1 of the RFI Protocol, in order to identify technical difficulties which might arise during a co-ordinated RFI measurement campaign over a period of 1 year. In this paper we describe the current equipment, observational technique and data presentation. The preliminary results demonstrate that the RFI situation at Dawodang depression in Guizhou province makes it quite a promising location for the proposed SKA. Furthermore, the first session of the RFI monitoring program, which was made in May 2004, showed that a complete RFI measurement including both modes 1 and 2 of the RFI Protocol would take about 2 weeks. The possible ways to minimize some limitations of the current equipment are also discussed, which will enable us to meet the RFI protocol.  相似文献   

Characterization of the mesospheric sodium layer at La Palma     

L. Michaille  J.B. Clifford  J.C. Dainty †  T. Gregory  J.C. Quartel  F.C. Reavell  R.W. Wilson  N.J. Wooder 《Monthly notices of the Royal Astronomical Society》2001,328(4):993-1000

We present the results of a mesospheric sodium monitoring programme at La Palma carried out through five campaigns of one week each, from 1999 September to 2000 August. The yearly averaged parameters of the layer (the sodium column density and the width) are given. We show that the short time-scale dynamics of the layer are governed by the sporadic layers with an average frequency of one event per night. The influence of the short time-scale dynamics of the layer on an adaptive optics system working on the William Herschel Telescope is quantified. It appears that it is a small effect in terms of defocus error. Finally, we present data obtained during the Perseid meteor shower and show that the dynamics of the sodium layer undergoes a transition with the meteoric activity.  相似文献   

丽江高美古的二期选址—筛选点的筛选     

钱铜铃汪从云  岑学奋王建成 《天文研究与技术》2001,(2):48-54

介绍了丽江高美古二期选址的筛选工作，经过踏勘确定高美古周围山头的10个点为筛选点，采用小型轻便望远镜于1998年10月16至1999年1月27日进行目视衍射环观测，并对取得的资料作了处理、分析和初步探讨。观测发现各点的视宁度没有明显差别，6  相似文献   

Late‐glacial and Holocene history of the dry forest area in the south Colombian Cauca Valley     

《第四纪科学杂志》2002,17(7):667-682

Two sedimentary cores with pollen, charcoal and radiocarbon data are presented. These records document the Late‐glacial and Holocene dry forest vegetation, fire and environmental history of the southern Cauca Valley in Colombia (1020 m). Core Quilichao‐1 (640 cm; 3° 6′N, 76° 31′W) represents the periods of 13 150–7720 ¹⁴C yr BP and, following a hiatus, from 2880 ¹⁴C yr BP to modern. Core La Teta‐2 (250 cm; 3° 5′N, 76° 32′W) provides a continuous record from 8700 ¹⁴C yr BP to modern. Around 13 150 ¹⁴C yr BP core Quilichao‐1 shows an active Late‐glacial drainage system and presence of dry forest. From 11 465 to 10 520 ¹⁴C yr BP dry forest consists mainly of Crotalaria, Moraceae/Urticaceae, Melastomataceae/Combretaceae, Piper and low stature trees, such as Acalypha, Alchornea, Cecropia and Celtis. At higher elevation Andean forest comprising Alnus, Hedyosmum, Quercus and Myrica was common. After 10 520 ¹⁴C yr BP the floral composition of dry forest changed, with extensive open grass vegetation indicative of dry climatic conditions. This event may coincide with the change to cool and dry conditions in the second part of the El Abra stadial, an equivalent to the Younger Dryas. From 8850 ¹⁴C yr BP the record from La Teta indicates dry climatic conditions relative to the present, these prevailing up to 2880 ¹⁴C yr BP at Quilichao and to 2720 ¹⁴C yr BP at La Teta. Severe dryness reached maxima at 7500 ¹⁴C yr BP and 4300 ¹⁴C yr BP, when dry forest reached maximum expansion. Dry forest was gradually replaced by grassy vegetation, reaching maximum expansion around 2300 ¹⁴C yr BP. After 2300 ¹⁴C yr BP grassy vegetation remains abundant. Presence of crop taxa (a.o. Zea mays), disturbance indicators (Cecropia) and an increase in charcoal point to the presence of pre‐Columbian people since 2300 ¹⁴C yr BP. After 950 ¹⁴C yr BP, expansion of secondary forest taxa may indicate depopulation and abandonment of previously cultivated land. After 400 ¹⁴C yr BP, possibly related to the Spanish conquest, secondary forest expanded and charcoal concentrations increased, possibly indicating further reduction of cultivated land. During the past century, Heliotropium and Didymopanax became abundant in an increasingly degraded landscape. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

滇西重力变化的二维图象及其与5级（M_s）以上地震的关系     

《大地测量与地球动力学》1995,(3)

  相似文献   

Model of optical turbulence profile at Cerro Pachón     

A. Tokovinin  T. Travouillon 《Monthly notices of the Royal Astronomical Society》2006,365(4):1235-1242

New measurements of optical turbulence profile at the Cerro Pachón observatory in Chile are analysed jointly with previously published data to model the variations of the intensity and thickness of the ground layer and free atmosphere under a variety of observing conditions. This work is motivated by the need to predict statistically the performance of ground-layer adaptice optics. We find that the ground-layer profile can be represented by a decaying exponent with a scale height of 20–40 m, increasing to 100 m under bad conditions. The zone from 6 to 500 m contributes typically about 61 per cent to the total integral, the latter causing a median seeing of 0.77 arcsec. Turbulence integrals in the ground layer and in free atmosphere vary independently of each other, in 50 per cent of cases they deviate by less than 1.8 times from their respective median values. The existence of periods with low turbulence in the free atmosphere and their importance for adaptive optics is stressed.  相似文献   

Investigations on the runoff generation at the profile and plot scales,Swiss Emmental     

Alexandre Badoux  Jonas Witzig  Peter F. Germann  Hans Kienholz  Peter Lüscher  Rolf Weingartner  Christoph Hegg 《水文研究》2006,20(2):377-394

This article describes an investigation on runoff generation at different scales in the forested catchment of the Sperbelgraben in the Emmental region (Swiss Prealps) where studies in the field of forest hydrology have a history of 100 years. It focuses on the analysis of soil profiles and the subsequent sprinkling experiments above them (1 m²), as well as on surface runoff measurements on larger plots (50 to 110 m²). In the Sperbelgraben investigation area, two very distinct runoff reactions could be observed. On the one hand, very high production of saturation overland flow was registered on wet areas of gleyic soils, with runoff coefficients between 0·39 and 0·94 for profile irrigation. On the other hand, almost no surface runoff was measured on Cambisols, with the exception at some sites of a hydrophobic reaction detected at the beginning of storms after dry periods (coefficients for profile irrigation: 0·01–0·16). This pattern was observed during 1 m² soil plot irrigation and on surface runoff plots. Apart from a less distinctive signal of the water‐repellent litter layer on the larger surface runoff plots, the dominant hydrological processes at the two scales are the same. The determined runoff reaction at the two scales corresponds well with information from a forest site type map describing soil and vegetation characteristics and used as a substitute for a soil map in this study. Theoretical considerations describing forest influence on flood discharge are discussed and evaluated to be in good agreement with observations. These findings are a sound foundation for application in hydrological catchment modelling. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献