1,720,965 research outputs found
Demographics and Seasonal Diet Composition of Shovelnose Sturgeon (Scaphirhynchus platorynchus Rafinesque) in Wabash River
Get PDFShovelnose sturgeon Schaphirhynchus platorynchus Rafinesque, one of the only sturgeon species that support a sustainable commercial harvest, are fished in a substantial caviar fishery in the lower Wabash River. However, ecological information on the population is sparse. In this thesis, I present information on the status and seasonal diet characteristics of the population. A 14-year long shovelnose sturgeon monitoring survey conducted by Illinois Department of Natural Resources shows that the population is in relatively good condition, faces low mortality rates, and has a high potential for recruitment. Study of the seasonal composition of diet suggests that shovelnose sturgeon generally get enough food throughout the year, and are thus, in good condition. I found that shovelnose sturgeon are opportunistic benthic invertivores, with Hydropsychidae and Chironomidae as the staple prey taxa for the fish. However, the sex-ratio of the population is highly male-biased, and the proportion of memorable-size fish is decreasing, likely due to the ongoing commercial harvest of ripe-and-running females. This poses potential problems regarding the sustainability of this fishery, and thus, management policies should be conservative until more information on optimal harvest of this fish is available
A Mechanistic Understanding of Range Expansion of Invasive Blue Catfish in the Chesapeake Bay Region
No full textBlue catfish Ictalurus furcatus is an invasive species of great concern in coastal habitats throughout the eastern United States, inclulding the Chesapeake Bay and its tributaries. In this dissertation, I use field surveys, laboratory experiments and quantitative modeling to provide insights into several aspects of blue catfish biology at the individual level. In chapter 1, I characterize and compare patterns in growth and body condition in blue catfish populations in the James and York river subestuaries during two stages of invasion. Both the mean growth rate and mean body condition of blue catfish declined in the recent period in response to increases in population abundance. In chapter 2, I uncover life-history plasticity in the reproductive biology of the species: blue catfish in the James River mature at a smaller mean size but provision a greater amount of energy into reproduction than York River fish, which exhibit lower densities than James River fish. In chapter 3, I assess the food demands of blue catfish in a laboratory experiment. I demonstrate that blue catfish have low metabolic demands, as expected for a relatively sedentary benthic fish. Importantly, blue catfish had high survival and significant growth at food levels as low as one third of the maximum, suggesting that the species has a high tolerance of starvation and that individuals may be able to invade and establish in low food habitats in coastal waters. In chapters 4 and 5, I report the results of two laboratory experiments studying the effects of increased salinity on survival, growth and body condition of blue catfish. Blue catfish, typically considered a freshwater species, was found to have a higher salinity tolerance (72-hour LC50 = 15.7 psu) than many freshwater fishes, suggesting the potential of the species to expand its range into most subestuaries of the Chesapeake Bay particularly during wet seasons. Habitats with salinities around 4 psu seemed particularly suitable for blue catfish as growth and body condition were maximized at this salinity despite the lower mean ingestion rates than fish maintained in freshwater. Finally, in chapter 6, I parameterize a full life-cycle bioenergetics model for female blue catfish using data from the literature and from the other chapters of this dissertation. The model supported the implications from other chapters that blue catfish have low maintenance costs, relatively high resistance to starvation and a plastic ability to fuel reproduction even in environments with low food availability. The model, together with results from other chapters, also opened up avenues for further research on characterization of the energetic basis for the observed phenotypic plasticity, identification of physiological modes of action by which salinity might limit survival, growth and reproduction of blue catfish, and ultimately the identification of coastal habitats that might support self-sustaining populations of this invasive fish. This research highlights the need for management efforts to control blue catfish populations in subestuaries where they are already established and to limit the range expansion into novel habitats. Towards this end, this dissertation provides important information on vital rates of blue catfish needed for population models that can be used for management strategy evaluations.Virginia Institute of Marine ScienceDoctor of Philosophy (Ph.D.
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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