1,721,012 research outputs found
Local habitat and seascape structure influence seagrass fish assemblages in the Venice lagoon: the value of conservation at multiple spatial scales.
No full textSeagrass meadows are a critical component of estuarine and coastal seascapes, and their structure influences fish assemblages at multiple spatial scales. The patch mosaic mode l, which defines the seascape as a collection of interacting habitat types, is increasingly dopted to prioritise protected areas and design ecological restoration schemes, hence helping to preserve seagrass meadows and the associated fish assemblages. Despite that, the re are few studies investigating the relative contribution of environmental characteristics measured at different spatial scales in determining the distribution of seagrass fish. This study collects fish and environmental observations taken at both site and seascape scales in seagrass meadows in the Venice lagoon (Adriatic Sea, Italy). By means of generalised linear models, it aims to disentangle the relative influence of local water qua
lity and habitat characteristics from that of habitat mosaic properties, investigating the response of whole fish assemblage descriptors, feeding guilds and dominant species. While confirming the primary importance of local habitat quality
, the study highlights that also seagrass habitat structure at the seascape scale is relevant for seagrass fish assemblages, influencing total biomass, biomass of macrobenthivorous and hyperbenthivorous/piscivorous species and seagrass specialists
such as syngnathids. Conservation of seagrass fish assemblages can therefore be promoted in Mediterranean coastal lagoons by preserving or restoring some features of the habitat mosaic, namely the extension of seagrass patches and their shape complexity, in addition to local water quality and seagrass cover
Uncertainty in developing fish based multi-metric indices
No full textThe process of development of a multi-metric index (MMI) implies a series of decisions to complete the procedure and obtain the formulation of an indicator. We performed an uncertainty and sensitivity analysis to explore the effects of alternative decisions in this process, using the case of fish fauna-based assessment of the ecological status in transitional waters and the Venice lagoon as an example. We formulated the alternative strategies in MMI implementation as levels of three factors affecting this procedure: 1) metrics pre-selection; 2) metrics numerical pre-treatment; 3) and metrics combination rules. The outcome of the uncertainty analysis highlighted that all the decisions impacted the process, potentially leading to indicators with different characteristics, confirming that the process of developing MMIs – even following an empirical data-driven approach – is not a completely objective procedure. However, not all the choices have the same weight in influencing the final index, nor do they affect the same characteristics of the index. The initial choice of candidate metrics influences the number of metrics included in the final index, the correlation of the MMI with anthropogenic pressures and the ecological status classification (i.e. the output of the index itself). However, the most influential decision is the one related to the criterion adopted to select the metrics (i.e. to reduce the number of metrics from the original candidate set) included in the final index. This choice is the one that most likely affects the structure of the index and the ecological status classification, even if the family of indices developed in this work exhibited a certain level of robustness regarding this characteristic
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
Predicting the response of fish and invertebrate assemblages to seagrass transplantations: assessment of the progress of habitat restorationin the Venice lagoon.
No full textOne of the major challenges to ensure effective restoration of estuarine habitats is to establish success criteria, allowingto determine whether the goalsof restoration are met. In the northern basin of Venice lagoon (northern Adriatic Sea, Italy), the LIFE project “SeResto” started in 2014 aiming at restoring seagrass meadows by means of small-scale manual transplantation of sods and rhizomes. The interventions are expected to increase the cover of Zostera marina and Z. noltei in the area, and to subsequently restore the typical features of faunal assemblages associated with seagrass meadows. The aim of this work is to propose a method to identify reference conditions and assess the progress of nekton (fish, decapods and cephalopods) assemblages at seagrass restoration sites.Nekton sampling took place from 2014 to 2017 during spring at eight transplantation sites. In spring 2016, five natural seagrass sites in the same area were additionally sampled, and physico-chemical water parameters and habitat structure (seagrass floristic composition, percent cover, canopy height, shoot density, leaf area index and epiphytal load) were also recorded. A multivariate approach based on GLMswas adopted, in order to disentangle the relative effect of water quality and seagrass habitat structure on nekton assemblages of natural habitats.Models were then employed to predict species composition of nekton fauna at each transplantation site under target abiotic and habitat conditions, allowing to identify the reference assemblages to evaluate the progress of fauna towards restoration goals. The analysis highlighted that desired restoration outcomes, i.e. presence of Z. marina and greater seagrass cover are positively linked to presence and density of some pipefishes (Syngnathidae), large gobies (Gobiidae) and some shrimps (Palaemonidae and Hippolytidae) in the nekton assemblage. Sites exhibiting better recovery of habitat structure also supported nekton assemblages more similar to reference conditions. However, none of the sites showed clear trajectories of progress, suggesting that more than three years are needed for nekton fauna to successfully colonise restored seagrass meadows in coastal lagoons
Fish response to multiple anthropogenic stressors in mediterranean coastal lagoons: A comparative study of the role of different management strategies
Full text linkTransitional waters are among the most productive ecosystems of the world and their biotic communities show high diversity and complex mechanisms of self-regulation that provide valuable ecosystem services and societal goods and benefits. In this work a comparison of the fish assemblages of three non-tidal Mediterranean coastal lagoons is carried out in order to evaluate the impacts of alternative management strategies. The anthropogenic pressures acting on the lagoons were quantified by means of categorical indicators, while the characteristics of the fish assemblages were summarized in multi-metric indices (MMIs). Two MMIs were developed using data collected with a beach seine net and with fyke nets, following an empirical approach that selects, from a pool of 73 metrics, the combination that maximizes the MMI/pressure relationship. The two MMIs include four metrics each, most of which are based on feeding mode functional guilds and habitat use functional guilds, and they are sensitive to anthropogenic pressures. The human activities directly or indirectly affecting water quality are the ones that most influence the fish assemblage, while the presence of artisanal fisheries, a typical and relevant resource use in these lagoons, seems to play a beneficial role. Lagoon fisheries management relies on the maintenance of infrastructures that guarantee the hydraulic functioning of the lagoon, thus ensuring exchanges with the adjacent coastal sea, and therefore indirectly contributing to the habitat quality
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
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