1,721,208 research outputs found
A simple management tool for planning the restoration of river longitudinal connectivity at watershed level: priority indices for fish passes
No full textThe present study aimed at defining and testing a simple and widely applicable management tool, based on already available or easily collectable data, which could allow Watershed Authorities to prioritize the interventions for river longitudinal connectivity restoration, reopening fish migration routes. The proposed priority indices for fish passes are based on obstacle characteristics, length of the potential reopened reach and fish species distribution and migratory behaviour. The indices were applied to two Italian watersheds (Arno and Magra Rivers) covering a total river length of more than 400 km. The priority lists produced by the application can function as a first step in defining a watershed restoration plan and could help the Watershed Authorities to address the available resources towards more detailed studies to be carried out at sites classified with the higher priority levels. This is the case of the Regional Natural Park Monte Marcello-Magra, where, within a recently funded LIFE+ project (P.A.R.C. –‘Petromyzon And River Continuity’), the first results of the priority indices application will be analyzed in greater detail and will consequently lead to the design and construction of fish passes to restore fish migration routes with a particular focus on sea lamprey (Petromyzon marinus).</p
Response of downstream migrating adult European eels (Anguilla anguilla) to bar racks under experimental conditions
No full textThe behavioural response of downstream migrating nonsalmonid fish to hydraulic conditions associated with river infrastructure is poorly understood. The response of downstream migrating adult European eels (Anguilla anguilla) to bar racks (12?mm bar spacing) angled on the vertical and horizontal planes under different flow regimes and during periods of darkness was assessed. Eels predominantly moved along the channel floor and wall, tending to follow routes where turbulence intensity was high. Time taken to approach the racks was greater than expected if fish had moved passively with the flow. Eels did not exhibit clear avoidance behaviour prior to encountering the racks, instead marked changes in behaviour occurred only after physical contact was made with the structure. No impingement or passage through the racks occurred, and passes per approach were high (98.3%), when vertical racks were angled 15°, 30° or 45° relative to the flow. Impingement and passage through the racks only occurred when horizontally inclined racks were placed perpendicular to the flow. The time eels were impinged on the racks was negatively related to discharge when angled at 30° relative to the channel floor, and positively related when upright. Frequency of impingement was higher under low discharge (132.9?±?16.6?l·s?1). Impinged eels escaped from racks at approach velocities of 0.90?±?0.05?m·s?1. Passage through the upright rack was common under high discharge (278.9?±?36.2?l·s?1). The information presented will improve current fish passage criteria for European eels that are required to develop more effective fish passage facilities. <br/
Success of a low-sloping rack for improving downstream passage of silver eels at a hydroelectric plant
No full textThe European eel (Anguilla anguilla) is a critically endangered species, and one major threat is the survival of silver eels migrating downstream towards the sea from lake and river rearing areas. During this migration, many eels are impinged and die on intake racks, or are injured or killed when passing through turbines. Intake racks at a hydroelectric plant were modified to avoid impingement and to collect eels without injury; high mortality on both racks and in turbines was previously documented. Modifications consisted of reducing the rack gap width from 20 to 18 mm, decreasing the rack slope from 63 to 35 degrees, increasing the rack surface area by 58% and installing six openings in the rack leading to traps. Downstream passage conditions for silver eels at the hydroelectric plant were significantly improved, reducing mortality from >70% at the old steep 20 mm racks to <10% at the modified 18 mm rack collection facility. No tagged eels were impinged and killed on the racks, and 80% entered the collection facility. Survival can probably be improved even more, as the individuals that passed the facility most likely escaped through holes in the traps. Moreover, injured untagged eels were still encountered at the modified racks, illustrating the need for rehabilitative measures to be implemented at all obstacles between the main eel rearing areas and the sea
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
Evaluating technical improvements for downstream migrating diadromous fish at a hydroelectric plant
No full textTechnicalimprovements to ameliorate downstream passage for diadromousfish have rarely been evaluated in regulated rivers in northern Europe. The current study evaluated rehabilitative measures for downstreammigrating Atlantic salmon, brown trout and European eel at ahydroelectricplant in southern Sweden. Smolts (N = 66), kelts (N = 20) and silver eels (N = 55) were caught, radio-tagged and tracked whilst passing the facilities in spring (salmonids) and fall (eels) of 2007. A surface gate in combination with a 90 mm-spaced turbine intake rack had afish guidance efficiency ranging from no effect for eels and trout smolts to 50% for trout kelts. A siphon discharging water from the bottom of the same 90 mm rack did not bypass any tagged fish, and only a few untagged eels. The poor function of the measures was attributed to the failure of the rack to stop smolts and eels from entering the turbines. The kelts, on the other hand, could not pass through the rack, and instead took a long time to locate the surface bypass entrance. The conditions for downstreammigratingfish have improved at the hydroelectricplant, but the total losses remain quite high for the studied groups (10-67%), and there is a need for a new rehabilitative measure that effectively allows all fish to bypass the turbine
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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