1,720,965 research outputs found
ANALYSE DU COMPORTEMENT DES TURSIOPS TRUNCATUS EN PRESENCE DE CHALUT - Influence of trawling on behaviour and Surfacing rates of bottlenose dolphin in northern thyrrenian sea
No full textLe grand dauphin (Tursiops truncatus) est une espèce opportuniste, principalement ichtyophage, pouvant se nourrir de poissons, céphalopodes et crustacés appartenant au domaine nectonique et benthonique. Les interactions entre pêche et grand dauphin sont fréquemment observées et
documentées, cela, quelques soient les techniques de pêche (Northridge et Hofmann, 1999). Ces interactions peuvent avoir d'importantes conséquences sur le rendement de la pêche et sur la conservation des cétacés (Perrin et al., 1994; Hall et Donovan, 2002). Cette étude analyse le comportement spécifique de l'espèce en présence de chalut. Les données relatives aux immersions/émersions enregistrées durant le suivi réalisé pour cette étude sont analysées de manière à
évaluer l'influence de la technique de pêche sur le comportement respiratoire de l'espèce. Cette étude,
réalisée dans l'Archipel toscan de 2005 à 2007, reporte 70 observations. Dans 33 % des cas, une interaction directe entre les dauphins et la chalutage a eut lieu. Dans l'Achipel toscan, le chalutage cible surtout les fonds de moins de 200m, et plus particulièrement les fonds inférieurs à 100m. Cette
étude prend pour exemple, cinq cas d'interactions et montre que généralement les animaux suivent la route linéaire du chalut seulement lors de la phase de chalutage. L'analyse statistique sur le comportement en surface des animaux indique une variation significative liée à la présence du
chalutage.
Bottlenose dolphin (Tursiops truncatus) is an opportunistic species that feeds both on nectonic and benthic preys such as cephalopods, crustaceans and fishes. Interactions between fisheries and bottlenose dolphins have been observed and well studied all around the world and for different fishing techniques (Northridge et Hofmann, 1999). The interactions lead to negative impacts both on fishing catch and on cetacean conservation ). This study deals with specific bottlenose dolphin behaviour in the presence of trawlers. We analysed surfacing behaviour during the monitoring dedicated to
determine how trawling influence bottlenose dolphin behaviour. Monitoring surveys took place in Tuscan archipelago from 2005 to 2007 during which 70 sightings have been collected. For 33% of sightings, we recorded direct interactions between dolphins and fisheries. In this area, trawling always occurred on sea bottom not deeper than 200m and preferably on 100m isobath. We paid attention to five cases of interactions. Results indicate that in all cases individuals follow the trawler's head only during haul. Surfacing pattern analysis indicates a significant difference between behaviour with and without trawlers
First assessment of the ecotoxicological status of Cuvier's beaked whale (Ziphius cavirostris) in the NW Mediterranean Sea
No full textCuvier's beaked whale (Cbw) is one of the least known species in the world. The Mediterranean subpopulation is ranked as Vulnerable (VU) in the “IUCN Red List of Threatened Species”, considering both the declining population trend both the low number of mature individuals estimated in the basin. While effects of underwater noise, known to be one of the main threats to the species, are being widely investigated, the ecotoxicological risk of the species is still unknown. The objective of this study is to
investigate for the first time the ecotoxicological status of Cbw in the NW Mediterranean Sea (Pelagos Sanctuary). The levels of organochlorine compounds (PCBs), polybrominated diphenyl ethers (PBDEs), and related biomarkers responses (induction of cytochrome's P450 CYP1A1 and CYP2B isoforms) were investigated in 22 skin biopsies from free-ranging organisms. This sample
set represent about the 20% of estimated size of the resident population in the area which has been monitored during the last fifteen years. All the animals were sexed and categorized into three different age classes (juveniles, subadults, adults) by both the estimated size and coloration patterns. CYP1A1 and CYP2B protein activity show different trends among different age groups and between sex. The contaminants analysis highlight that the average abundance pattern for the target contaminants was PCBs>PBDEs and the concentration values are linked to age and sex, with males showing higher levels (∑PCBs 23.77 mg/kg
l.w., ∑PBDEs 0.516 mg/kg l.w.) than females (∑PCBs 8.08 mg/kg l.w.,l ∑PBDEs 0.172 mg/kg l.w.). 80% of sampled cbw had PCB concentrations above the toxicity threshold for physiological effects in marine mammals, suggesting a potential effect on this mediterranean population fitness. This study represents an important step forward in our understanding of the effects of toxic
compounds in combination with other known or suspected threats to this population of Cuvier's beaked whale
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
