1,721,000 research outputs found
Dataset for Impact of tide gates on the upstream movement of adult brown trout
No full textThree-hundred adult trout were caught between 0.5 and 6.0 km upstream from tide gates in the River Stiffkey, North Norfolk, UK, on 20 separate days between July and December 2011 (n = 15 per day) and implanted with 23 mm half-duplex Passive Integrated Transponder (PIT) tags before being released 15 m downstream from the gate where PIT antennas were located on either side. Overall, gate attraction (percentage of fish released that were detected by at least one antenna) and passage efficiencies (number of fish that passed Gate 1 reported as a proportion of those that approached) were 96.7% and 92.4%, respectively. The operation of an orifice, installed to improve connectivity for adult trout and juvenile eels, did not influence passage efficiency or delay. Of the fish that passed the gate when the orifice was operational, 42.6 - 55.7% approached the orifice entrance and 70.6 - 92.3% of these passed through. Individuals that passed through the orifice were larger than those that did not. Movement past the tide gates (median duration = 6.04 h) took 6 times longer than passage through two unimpeded reaches upstream. Duration of passage through the gates was predominately related to the mean angle of gate opening during the time prior to passage, followed by water temperature.</span
The impact of an Archimedes screw hydropower turbine on fish migration in a lowland river
No full textThere has been an increase in the abundance of small hydropower (< 10 MW) installations. These tend to be ‘run-of-river’, thereby reducing or averting the need for impoundment and water storage, and so are considered to have lower environmental impact. The Archimedes screw turbine (AST) has been described as ‘fish friendly’ based on magnitude of observed first order impacts, i.e. low rates of direct damage and mortality due to blade strike. However, potential second order effects, such as altered fish behaviour prior to or after passage, and
consequences for long-term survival and fitness, have been largely ignored. This two-year study employed acoustic and Passive Integrated Transponder (PIT) telemetry and dual frequency imaging sonar to investigate the influence of an AST and associated fish passes (Larinier super-active baffle pass and upstream eel ladders) on the movement patterns and behaviour of five species of potadromous fish and European eel (Anguilla anguilla). Seaward-migrating adult (silver) eels successfully descended the AST, but under high flows most individuals
took an alternative route via an overshot weir which resulted in faster passage rates. There was no immediate silver eel mortality as a result of passage through the turbine and no effect on subsequent migration behaviour through the lower freshwater catchment and estuary. Some eels were delayed at the complex and exhibited frequent rejection and milling on their approach to the AST and fish passes. Upstream passage rate (%) at the Larinier pass varied among species with highest for dace (81%) and the lowest for roach (10%). Fish that aggregated up- and downstream of the AST rapidly dispersed on turbine start-up. Although ASTs can be considered a potential downstream passage route for both eels and potadromous species, adult eels milled and rejected at the upstream entrance, while other fish exhibited startle response on turbine start-up. Potential delay
to seaward migration of silver eel and the energetic costs of observed behaviours should be considered during future impact assessments, particularly where there is no alternative migration route or there are multiple such facilities in a watercourse
Impact of tide gates on the migration of adult European Eels, Anguilla anguilla
Full text linkTide gates form a temporal barrier to fish migration, closing during the flood tide and opening during the ebb, primarily for flood prevention and land reclamation. Their impact on downstream adult migration of the critically endangered European eel, Anguilla anguilla, is unknown. The River Stiffkey, UK, has three top-hung tide gates (one counterbalanced, two not) through which it discharges into the North Sea. Adult eels of silver appearance (n?=?118) were caught between 0.5 and 6.0 km upstream from the tide gates in Autumn 2011 and implanted with 23 mm half-duplex passive integrated transponder (PIT) tags. Tagged individuals were detected by PIT antennae located near the tide gates. Of the eels tagged, 80 were detected actively migrating downstream to the gates. Escapement past the gates was 98.3 %. Speed of migration was slower near the gates than for an unimpeded upstream reach and was positively and negatively related to mean degree of gate opening and mean light intensity, respectively. When the largest gate was modified through installation of an orifice intended to improve upstream passage of sea trout and juvenile eels, downstream migration was more rapid when it was operating. However, video analysis revealed that eels did not pass through the orifice, meaning that faster migration may have been a result of the gates being open on more occasions when eels initially approached them, or the lower tides and upstream saline intrusion that occurred during these periods. Top-hung tide gates in the River Stiffkey delayed eel migration, potentially increasing the risk of predation and energy expenditure immediately prior to a 5000–6000 km migration to spawning grounds in the Sargasso Se
Impact of tide gates on the migration of juvenile sea trout, Salmo trutta
No full textAs part of flood protection and land reclamation schemes, tide gates allow rivers to discharge to sea when open, and prevent salt water intrusion when closed. Their impact on diadromous fish migration between essential spawning and rearing habitats, and the effectiveness of mitigation measures, have received little consideration. The River Meon, UK, discharges to sea through four top-hung counterbalanced tide gates. In March 2012, the gates were replaced with new ones of the same design, but with an orifice installed in two of them partly to improve fish passage. Sixty downstream migrating juvenile sea trout, Salmo trutta, were trapped approximately 4.9 km upstream of the tidal limit and tagged with acoustic transmitters in April 2011 (n = 30) and 2012 (n = 30). Tagged individuals were detected by acoustic receivers placed near the tide gates before (year 1) and after (year 2) orifice installation. Of the fish that approached the tide gates, 95.8% and 100.0% successfully passed in years 1 and 2, respectively. The speed of migration at the gates was slower than for upstream and downstream reaches, and was positively related to percentage of time the gates were open. Presence of the orifices did not influence delay. Overall, top-hung tide gates delayed sea trout migration, potentially increasing the risk of predation and energy expenditure during the vulnerable juvenile life stage
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
Impact of tide gates on the upstream movement of adult brown trout, Salmo trutta
No full textTide gates, used to regulate tidal flow as part of land reclamation programmes, temporally block fish movement by closing during the flood tide. Their impact on the upstream movement of brown trout, Salmo trutta, and other fish species has received little consideration. The River Stiffkey, UK, discharges into the North Sea via three top-hung tide gates, one counterbalanced (Gate 1), and two not (collectively referred to as Gate 2). Three-hundred adult trout were caught between 0.5 and 6.0 km upstream from the gates on 20 separate days between July and December 2011 (n = 15 per day) and implanted with 23 mm half-duplex Passive Integrated Transponder (PIT) tags before being released 15 m downstream from Gate 1 where PIT antennas were located on either side. Overall, gate attraction (percentage of fish released that were detected by at least one antenna) and passage efficiencies (number of fish that passed Gate 1 reported as a proportion of those that approached) were 96.7% and 92.4%, respectively. The operation of an orifice, installed to improve connectivity for adult trout and juvenile eels, did not influence passage efficiency or delay. Of the fish that passed Gate 1 when the orifice was operational, 42.6–55.7% approached the orifice entrance and 70.6–92.3% of these passed through. Individuals that passed through the orifice were larger than those that did not. Movement past the tide gates (median duration = 6.04 h) took 6 times longer than passage through two unimpeded reaches upstream. Duration of passage through the gates was predominately related to the mean angle of gate opening during the time prior to passage, followed by water temperature. Overall, a counterbalanced top-hung tide gate delayed the upstream movement of brown trout, highlighting a need to assess and potentially mitigate the impact of gates with more restrictive opening apertures and durations
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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