1,720,991 research outputs found
Charting Progress 2. Chapter 3. Healthy and Biologically Diverse Seas:Seals
No full text3.5.1 Key pointsi. IntroductionTwo species of seal live and breed in the UK.About 36% of the world’s population of greyseals reside in the UK; almost 90% of these arein Scotland. About 4% of the world’s populationor 30% of the European subspecies of harbour(also known as common) seal are found in theUK with 80% of these in Scotland. Althoughboth species can be seen all round the UKcoast, they are considerably more abundant insome areas than others. Changes in local sealpopulation size and distribution may be relatedto changes in the marine environment. Underthe Conservation of Seals Act 1970, the NaturalEnvironment Research Council has a statutoryobligation to provide the UK Governmentwith ‘…scientific advice on matters relatedto the management of seal populations’. Amajor component of this advice is up-to-dateinformation on the size and distribution of UKseal populations. Both grey and harbour sealswere given protection under the Conservationof Seals Act 1970 and under the EU HabitatsDirective. In Scotland, the Conservation of SealsAct has been replaced by the Marine (Scotland)Act 2010, which has extended seal protectionmeasures.Five species of Arctic seal occasionally visit theUK coast.ii. How has the assessment beenundertaken?UK seal populations are monitored by differentorganisations using a variety of techniques. Greyseal populations are assessed through estimationof pup production at traditional breedingcolonies. Pup production is monitored annuallyat colonies that contribute an estimated 85% ofpups born in the UK. Most colonies are surveyedusing aerial photography, others through groundcounting. The great majority of colonies in Walesand south-west England are not included as theyare extremely difficult to survey and cannot besurveyed frequently because grey seals breed incaves or on beaches at the foot of remote cliffs.Harbour seal populations are also monitoredmostly by aerial survey, although at a differenttime of their annual cycle since they do notaggregate when breeding. In south-east Englandand parts of Scotland they are monitoredannually. In the remainder of Scotland they aremonitored at about four to five year intervals. InNorthern Ireland, counts are monthly. Grey sealpup production has been monitored since theearly 1960s; harbour seals have been monitoredsince the late 1980s. Both grey and harbourseals are probably more numerous now thanin the historical past, when they were locallyhunted and/or harvested.iii. Current and likely future status of sealpopulationsIn the UK, grey seals are considerably morenumerous than harbour seals. After decadesof increase, total grey seal pup productionappears to be levelling off in the UK and is nowincreasing at only a small number of colonies.Harbour seal numbers have declined dramaticallyin Shetland, Orkney and the east coast ofScotland since 2001, by over 50%. There hasbeen a smaller decline in the Outer Hebrides butnumbers on the west coast of Scotland haveremained relatively stable. The causes of thesedeclines are not yet known. Two outbreaksof phocine distemper virus (PDV) affected theharbour seal population in eastern England with50% dying in 1988 and 22% dying in 2002.In marked contrast to European harbour sealpopulations which showed an immediate andrapid recovery, recovery in the eastern England508 Healthy and Biologically Diverse Seaspopulation after the 1988 outbreak was delayedfor three years and has yet to begin followingthe 2002 outbreak. PDV outbreaks are likelyto recur in the future but it is not possible topredict the proportion of the population thatmight be affected, which populations are mostvulnerable (besides eastern England) or preciselywhen outbreaks will occur.iv. What is driving change?The previous increase in grey seal pupproduction is at least in part due to the increasedavailability of breeding sites following theabandonment of human settlements on remoteislands, including the automation of lighthouses.The current reduction in the rate of increaseis thought to be due to density dependentfactors affecting the population as a whole. It isnot yet clear whether factors affecting survivalare more important than factors affectingfecundity. Causes of the declines in harbour sealpopulations in north and east Scotland remainunclear. Contributing factors could be eithernatural or anthropogenic or both and include:competition with grey seals, predation by killerwhales, unregulated shooting and declines inimportant prey species (e.g. sandeels).It is difficult to predict future trends in UKseal populations with certainty. Grey seal pupproduction appears to be stabilising, so thegrey seal population is likely to stabilise overthe next decade or so. It is far harder to predictwhat harbour seal populations in north and eastScotland will do, given recent declines and thelack of any obvious cause(s). In east England,PDV outbreaks are likely to recur in the future.The observed recent declines in north and eastScotland populations are not related to theoutbreak of PDV in 2002 as none of the harbourseals sampled in areas of decline had beenexposed to PDV.v. What are the uncertainties?While there are uncertainties in estimatingthe size of the total grey seal population fromthe annual estimates of pup production, theprocedures used to estimate pup productionare considered to be robust. Through the1970s, 1980s and early 1990s, seal researchwas focussed heavily on grey seals, withharbour seals only coming to attention in1988, after the first PDV outbreak. With therecently documented declines, harbour sealsare becoming increasingly important. Most ofthe pressure assessment is based on expertjudgement but it is difficult to assess the effectsof different pressures on seal populations. Thisapplies to both species.vi. Forward lookThe Scottish Government and Scottish NaturalHeritage have funded a number of projectsinvestigating the declines in harbour seals innorth and east Scotland. Increasing renewableenergy production may impact marine mammalpopulations, requiring additional information incertain areas. Harbour seal monitoring frequencyin Scotland is infrequent compared with greyseal monitoring
Breeding and moulting season surveys of common (harbour) seals (Phoca vitulina) around Scotland, excluding the Northern Isles
No full text
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
- …
