1,720,972 research outputs found
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
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
Food Web Interactions Among Walleye, Lake Whitefish, and Yellow Perch in Green Bay, Lake Michigan
No full textGreen Bay supports important fisheries for walleye Sander vitreus, lake whitefish
Coregonus clupeaformis, and yellow perch Perca flavescens. While walleye and lake whitefish
populations have expanded in Green Bay, yellow perch numbers remain at historically low
levels. As one of the primary piscivores in the Green Bay food web, walleyes could influence
lake whitefish and yellow perch abundance, and yellow perch are important prey for walleye
within many ecosystems. Specifically, walleye and yellow perch populations in southern Green
Bay have exhibited contrasting trends in abundance since 1986. Walleye predation has been
hypothesized to represent a potential recruitment bottleneck for yellow perch in Green Bay,
which has been documented in other areas throughout the Great Lakes.
These three species likely interact in a variety of ways, including predation and diet
overlap, but these interactions are poorly understood because contemporary information on diets
is lacking. This information is needed to guide management decisions, because changes in
population status of one species will likely affect fisheries for the other two species. The specific
objectives of my research were to determine if: 1) lake whitefish and yellow perch represent
important prey for walleyes in Green Bay; 2) diets of these three species vary spatially and
temporally; 3) diet overlap among species is evident; and 4) the extent of walleye predation is
sufficiently high to influence recruitment potential of lake whitefish and yellow perch in the
portion of Green Bay south of Chambers Island (Zone 1).
Fish were collected each month from May through October in two zones of Green Bay
during 2018 and 2019 using monofilament graded mesh gill nets. Additional fish were collected
by natural resource agencies, commercial fishers, and recreational anglers. A total of 4,423
stomachs were dissected and diet items were removed and wet weighed to generate diet
compositions using diet information from 687 walleye, 533 lake whitefish, and 696 yellow perch
with nonempty stomachs. For each species, diet composition was described using mean
proportion by wet weight for each year, zone, and month combination. Analysis of similarities
(ANOSIM) was used to test for spatial and temporal differences in diet composition, Pianka’s
(1974) index of niche overlap was used to calculate the extent of diet overlap, and a combination
of bioenergetics and statistical catch-at-age (SCAA) modeling was used to estimate total walleye
consumption of lake whitefish and yellow perch from May 1 through October 31 during 2018.
Diet compositions suggest that lake whitefish and yellow perch comprise between 5-6%
of walleye diets overall, though temporal and spatial variation in diets was evident. Lake
whitefish were seasonally important prey consumed only during May and June in Zone 1,
comprising 36% of June walleye diets. Also, this study was the first to document the importance
of lake whitefish to walleye diets within the Great Lakes. In both zones, yellow perch
contributed to walleye diets at a broader temporal scale than lake whitefish, but perch never
comprised more than 15% of walleye diets in any month throughout Green Bay.
Walleye diet compositions were significantly different between zones, potentially
reflecting differences in prey fish availability. Additionally, significant temporal variation was
identified in Zone 1, with distinct seasonal transitions in the consumption of prey species.
Walleye diets were generally similar between 2018 and 2019, though fish collections during
2019 occurred at a reduced scale. Furthermore, variability in diet compositions was less evident
for lake whitefish and yellow perch. However, a significant difference was detected between
zones which was attributed to the greater contribution of round gobies Neogobius melanostomus
in lake whitefish and yellow perch diets identified in Zone 2. Similarly, a significant temporal
change in yellow perch diets was detected, largely attributed to increased consumption of round
gobies during the fall throughout Green Bay.
Diet overlap was strongest between lake whitefish and yellow perch, while weak to
moderate overlap was observed between walleye and both lake whitefish and yellow perch. The
highest degree of diet overlap between walleye and yellow perch occurred during October in
Zone 1, corresponding with increased contribution of gizzard shad Dorosoma cepedianum to the
diets of both species, and September in Zone 2, which was influenced most by predation on
round goby and yellow perch. Moreover, diet overlap was highly influenced by the invertebrate
prey group used in my diet analyses, as all invertebrate taxa were pooled. More specific
identification of invertebrate taxa in diets would likely increase the resolution and reliability of
my diet overlap indices, but this would be difficult because invertebrates were rarely intact in
many diets, especially for lake whitefish.
In conjunction with observed growth and monthly diet data, a range of abundance
estimates (i.e., 95% confidence limits) from SCAA models were used to predict the influence of
walleye predation on lake whitefish and yellow perch recruitment potential. Based on the range
of walleye consumption estimates and lake whitefish recruitment estimates, walleye
consumption appeared unlikely to influence recruitment potential of lake whitefish in Zone 1 of
Green Bay. However, given the high abundance of walleye and low abundance of yellow perch
estimated in Zone 1, yellow perch recruitment potential is likely affected by walleye predation.
These results corroborate other studies that have identified walleye predation as a
significant recruitment bottleneck for yellow perch populations throughout the Great Lakes. This
study also suggests that previous concerns related to walleyes negatively impacting lake
whitefish may be unrealistic. Additionally, alewife Alosa pseudoharengus, gizzard shad, and
invasive round gobies may serve as predation buffers for lake whitefish and yellow perch and
predation by my three focal species may help in regulating round goby abundance in Green Bay.
My results provide fisheries managers and stakeholders with important information regarding the
complex interactions among walleyes, lake whitefish, and yellow perch in Green Bay, so that
future management decisions can be made with a better understanding of the potential
implications for all three fisheries and prey resources
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
Movements and Spawning Habitat of Muskellunge Esox Masquinongy in Green Bay, Lake Michigan
No full textMuskellunge (Esox masquinongy) have been extirpated or have declined significantly in many areas of the Great Lakes, including Green Bay. Restoring a self-sustaining population of Muskellunge to Green Bay is a goal of several management efforts. Currently, annual stocking supports a world-renowned trophy fishery for anglers seeking to catch large Muskellunge. However, there has been limited evidence of natural reproduction as few juvenile Muskellunge of wild origin have been collected. Lack of juvenile Muskellunge in Green Bay suggests natural recruitment is limited, possibly due to habitat limitations. Previous work has identified potential Muskellunge spawning locations in Green Bay and provided initial descriptions of Muskellunge spawning habitat, but it is not known whether Muskellunge successfully hatch at these locations or what habitat characteristics result in successful hatching. Additionally, it is not known if Muskellunge in Green Bay exhibit reproductive homing and return to the same locations to spawn in consecutive years, or if Muskellunge return to their stocking location to spawn. Due to the uncertainties surrounding Muskellunge reproduction in Green Bay, my objectives were to determine if: 1) Muskellunge spawning locations and occurrence of successful hatching were related to habitat variables, 2) proportions of Muskellunge spawning in or outside of tributaries to Lower Green Bay were different, 3) most Muskellunge (>75%) returned to stocking locations to spawn, and 4) adult Muskellunge display high site fidelity (>75%), returning to the same locations to spawn in consecutive years. Results from my research allowed me to quantify the availability of suitable spawning habitat in the Fox and Menominee rivers, and to qualitatively characterize general movement patterns of Muskellunge in Green Bay and its tributaries. My study was the culmination of a 4-year effort focusing on Muskellunge spawning behavior and success in southern Green Bay and its tributaries. During 2017-2019, adult Muskellunge (N = 60) were captured and surgically implanted with radio and acoustic transmitters. Muskellunge were actively tracked during the open water season to identify putative spawning sites using a combination of aerial and boat-based telemetry. Muskellunge were also monitored passively using acoustic receivers at fixed locations. Egg sampling was conducted at putative spawning site using an airlift pump, followed by larval sampling using conical ichthyoplankton nets, D-frame nets, and quatrefoil light traps. Habitat variables were recorded at each putative spawning site and at a large number of random sites that were also sampled for eggs. Multiple logistic regression was used to model the habitat variables significantly influencing the probability of Muskellunge egg presence at a given location. Data from acoustic receivers and active tracking efforts were used to determine seasonal movement patterns and tributary use of Muskellunge. Chi-square tests were used to compare proportions of Muskellunge spawning in tributary vs. bay habitats, as well as analyze reproductive homing to stocking locations and spawning site fidelity. Side-scan sonar in combination with my logistic regression model was used to quantify the amount of suitable Muskellunge spawning habitat in the Fox and Menominee rivers. In total, 278 sites were sampled for eggs, and as a result 58 egg sites were identified. Additionally, 436 individual sampling events resulted in the capture of two larval Muskellunge. Because only two larval Muskellunge were captured, I was not able to quantify habitat characteristics related to successful hatching. Therefore, my final logistic model only includes habitat variables related to egg deposition. My final logistic regression model indicates bottom slope, depth, dissolved oxygen, distance from shore, percent of gravel substrate, and percent of organic matter as a substrate best predict Muskellunge egg presence at a given location. Of these habitat variables, bottom slope had the greatest influence on presence of Muskellunge eggs. The likelihood Muskellunge eggs were present at a given site decreased by 50% when slope steepness increased by 0.5 m/m. A 1-m increase in depth resulted in a 49% decrease in probability Muskellunge eggs were present. A one unit increase in the dissolved oxygen concentration (1 mg/L) at a given site increased the probability Muskellunge eggs were present 1.4 times. Additionally, for every 1 m increase in distance to shore the probability of Muskellunge egg presence decreased by 14%. Finally, a 10% increase of gravel or organic matter in the substrate increased the probability of Muskellunge egg presence by 27% and 19%, respectively. Currently, based on surface area, 1.3% of the Fox River and 8.3% of the Menominee River are suitable Muskellunge spawning habitat (suitable for egg deposition). Proportions of Muskellunge spawning in or outside of tributaries were not significantly different in 2018, 2019, or 2020 based on chi-square analysis. Of the Muskellunge spawning in tributaries to Green Bay during my study, the majority spawned in the Fox River. Telemetry data suggest Muskellunge are spawning in the Fox, Menominee, Suamico, and Peshtigo rivers, and potentially in Duck Creek. Eggs were collected to confirm spawning in the Fox, Menominee, Suamico, and Peshtigo rivers and in multiple locations throughout Green Bay proper. In all but one case, Muskellunge with known stocking locations (N = 6) returned to their stocking location to spawn. Finally, Muskellunge in Green Bay displayed moderate levels of spawning site fidelity (45-70%), and the upper proportion of this range was not significantly different than 75%. Muskellunge in Green Bay generally moved south towards the mouth of the Fox River as water temperatures cooled in fall. A handful of Muskellunge overwintered in the Fox River in 2018, 2019, and 2020. Peak spring spawning activity was observed at water temperatures comparatively higher to reported Muskellunge spawning activity in most locations. Entry into tributaries for spawning each spring was staggered over a long period of time prior to peak spawn, whereas exit out of tributaries after presumed spawning was comparatively more truncated. In the Fox River, average residency times for each year were 27, 27, and 21 days respectively, with males generally residing longer than females. My results demonstrate that habitat suitable for Muskellunge egg deposition may be lacking in the Fox and Menominee rivers. Additionally, the lack of Muskellunge larvae captured during my study suggests that successful hatching may not be occurring in Lower Green Bay and the Fox River or is occurring at relatively low levels. A lack of naturally produced recruits indicates the Green Bay Muskellunge population is not self-sustaining, and stocking is still required to support the current fishery. My results also demonstrate that choice of stocking locations may play an import role as a management tool, as Muskellunge are likely to return to stocking locations to spawn and generally display moderate site fidelity. Stocking Muskellunge in tributaries at shallow areas with minimal human alteration of the shoreline may result in increased egg deposition and subsequent natural reproduction. Furthermore, stocking Muskellunge in Green Bay proper at sites closely resembling wetland or coastal marshes, such as in Deadhorse Bay, may increase Muskellunge spawning in these locations and lead to successful hatching. Due to the proportion of Muskellunge in Green Bay not spawning in tributary habitats, known spawning areas in Green Bay proper should be considered for enhancement or protection efforts in addition to those in tributaries. Management objectives and goals related to the Green Bay Muskellunge population should emphasize actions that result in increased knowledge of factors regulating successful hatching, enhancement and protection of suitable spawning habitat, and identifying natural reproduction
Genetic Assessment of Boardman River Fish Populations Before Dam Removal
No full textThe genetic assessment of fish populations in the Boardman River, MI presented here incorporated two unique approaches to address a variety of questions about population structure and species richness in this system. These two research projects are presented as two distinct chapters in this thesis, and each respective abstract is given below.
Fragmentation of river systems by dams can have a substantial genetic impact on fish populations. However, genetic structure can exist naturally at small scales through various processes such as isolation by adaptation (IBA) and spawning site fidelity, even in the absence of barriers. We sampled individuals from five native fish species with varying life histories above and below a dam in the lower Boardman River, Michigan, USA, and used RADseq to test whether genetic structure was influenced by the dam or other processes. Species assessed were white sucker Catostomus commerson, yellow perch Perca flavescens, walleye Sander vitreus, smallmouth bass Micropterus dolomieu, and rock bass Ambloplites rupestris. We detected significant differentiation within each species, but this structure did not appear to be a result of fragmentation by the dam. Population groupings were not consistent with our original “above dam” and “below dam” sampled populations, but instead aligned with a Great Lakes (GL) group from Lake Michigan and a Boardman River (BR) group that appear to mix below the dam. We hypothesize that these groups formed prior to dam construction through IBA in these different habitats and further maintained divergence through spawning site fidelity. Additionally, GL fish for most species were significantly smaller in length than BR fish, suggesting a potential ontogenetic habitat shift of young GL fish into the lower river for feeding and/or refuge. Without our genetic assessment, the existence of these cryptic ecotypes likely would have continued undetected. Our study illuminates the importance of tributary habitats for GL fish and has major implications for the management of fish populations in the Great Lakes and beyond. Finally, our approach of combining genetic data, ecological data, and simulations to assess connectivity and identify cryptic diversity has far reaching applicability for understanding the potential genetic impacts of fragmentation in other systems.
Understanding biodiversity in aquatic systems is critical to ecological research and conservation efforts, but accurately measuring species richness using traditional methods can be challenging. Environmental DNA (eDNA) metabarcoding, which uses high-throughput sequencing and universal primers to amplify DNA from multiple species present in an environmental sample, has shown great promise for augmenting results from traditional sampling to characterize fish communities in aquatic systems. Few studies, however, have compared exhaustive traditional sampling with eDNA metabarcoding of corresponding water samples at a small spatial scale. We intensively sampled Boardman Lake (137 ha) in Michigan, USA from May to June in 2019 using gill and fyke nets and paired each net set with lake water samples collected in triplicate. We analyzed water samples using eDNA metabarcoding with 12S and 16S fish-specific primers and compared estimates of fish diversity among methods. We captured a total of 12 fish species in our traditional gear and detected 40 taxa in the eDNA water samples, which included all the species observed in nets. The 12S and 16S assays detected a comparable number of taxa, but taxonomic resolution varied between the two genes. In our traditional gear, there was a clear difference in the species selectivity between the two net types, and there were several species commonly detected in the eDNA samples that were not captured in nets. Finally, we detected spatial heterogeneity in fish community composition across relatively small scales in Boardman Lake with eDNA metabarcoding, but not with traditional sampling. Our results demonstrated that eDNA metabarcoding was substantially more efficient than traditional gear for estimating community composition, highlighting the utility of eDNA metabarcoding for assessing species diversity and informing management and conservation
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