1,721,044 research outputs found
Le Carte Ittiche: stato del monitoraggio dell'ittiofauna sul territorio nazionale - Freshwater Fish Maps for the fisheries management in Italy: state of the art
No full textÈ opinione comune che la protezione e la conservazione degli ecosistemi, nonché lo sviluppo dell’ambiente, debba essere garantito dalle amministrazioni pubbliche attraverso l’integrazione delle conoscenze scientifiche e la collaborazione attiva dei cittadini. La pesca costituisce uno degli ambiti in cui gli enti pubblici sono chiamati a svolgere una funzione di pianificazione dell’uso sostenibile delle risorse naturali. In questo contesto l’ittiofauna delle acque interne è un bene dello Stato e come tale va tutelato e amministrato. Senza l’analisi delle popolazioni ittiche e dell’ambiente acquatico, non solo si rischia di alterare drasticamente la funzionalità degli ecosistemi acquatici ma si ha anche uno spreco dal punto di vista economico. I sistemi acquatici, soprattutto quelli delle Province meridionali, sono molto instabili e la distribuzione e la densità delle singole popolazioni ittiche é valida solo per il periodo in cui viene effettuato il campionamento, per cui si rendono necessari periodici monitoraggi. Sono ormai diversi anni che le Regioni e le Province del territorio nazionale hanno intrapreso iniziative tese ad acquisire le conoscenze scientifiche per poter definire i programmi di gestione e conservazione degli ambienti acquatici. Le Carte Ittiche rappresentano lo strumento per una pianificazione e per una gestione razionale dell’ittiofauna e delle attività alieutiche, permettendo una proficua convivenza tra pesca sportiva e salvaguardia del patrimonio ittico (A.I.I.A.D., 1993). Lo scopo di questo lavoro è quello di esporre la situazione del monitoraggio della fauna ittica attraverso la ricerca delle Carte Ittiche disponibili nelle varie Regioni e/o Province italiane, confrontando tra loro quelle redatte in ambito regionale
Movement and Activity Patterns of Non-Native Wels Catfish (Silurus glanis Linnaeus, 1758) at the Confluence of a Large River and Its Colder Tributary
Full text linkThe establishment and proliferation of non-native fish species can have a range of effects within the local ecosystem, including alteration of food webs, nutrient cycling, pathogen dynamics and predation, sometimes also resulting in changed behavior and distribution of native fish species. Knowledge about movements and activity patterns is important to understand the dynamics of non-native animals in their new environment. The Wels catfish (Silurus glanis Linnaeus, 1758) is considered an invasive species in many places in Western Europe, and regional control programs are in place. Here, using radiotelemetry, we study the movements and activity patterns of invasive Wels catfish at an invasion front within the Po River (Italy); namely, at the confluence between the main river, where the species is abundant, and a colder tributary, the Dora Baltea River, where it is absent. In addition, we also investigate potential spatiotemporal overlap between Wels catfish and native and endangered marble trout (Salmo marmoratus Cuvier, 1829) in the area. A total of nine Wels catfish and eight marble trout were tagged. The Wels catfish showed a very high degree of residency within the study area in the Po River, close to the mouth the colder tributary. Despite this, only one catfish entered the lower reaches of the tributary and did so only occasionally during August. No catfish moved further upstream in the tributary. It is likely that lower temperatures in combination with more challenging hydrodynamic conditions made the tributary unattractive to the catfish. The catfish were active during all times of the day but substantially more so during evenings and at nights. Some, but not all, tagged catfish moved to areas in the main stem upstream of the confluence with the tributary. A large proportion of the tagged marble trout made occasional or longer visits to the Po River, with several individuals becoming resident, but without apparent mortality, in the tagged catfish home range. The high residency of the Wels catfish suggests that removal efforts may do well to initially focus on areas close to the habitats of species under conservation concern
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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
Valutazione del grado di contaminazione in PCB in siluri (Silurus glanis) pescati nel bacino idrografico del fiume Po (Provincia di Alessandria, Italia nord - occidentale)
No full text- …
