Laura L. E. Cowen

Laura L. E. Cowen
University of Victoria | UVIC · Department of Mathematics and Statistics

PhD

About

34
Publications
4,284
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500
Citations
Introduction
Laura L. E. Cowen currently works at the Department of Mathematics and Statistics, University of Victoria. Laura does research in Ecology and Statistics. Their most recent publication is 'Is Ocean Reflectance Acquired by Citizen Scientists Robust for Science Applications?'.
Additional affiliations
September 2000 - April 2005
Simon Fraser University
Position
  • Research Assistant

Publications

Publications (34)
Article
Asymptomatic and pauci-symptomatic presentations of COVID-19 along with restrictive testing protocols result in undetected COVID-19 cases. Estimating undetected cases is crucial to understanding the true severity of the outbreak. We introduce a new hierarchical disease dynamics model based on the N-mixtures hidden population framework. The new mode...
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Full-text available
• Capture–recapture experiments are conducted to estimate population parameters such as population size, survival rates, and capture rates. Typically, individuals are captured and given unique tags, then recaptured over several time periods with the assumption that these tags are not lost. However, for some populations, tag loss cannot be assumed n...
Article
Full-text available
We develop a new method for estimating population abundance for notoriously difficult to count populations. This is made possible using an easy to count auxiliary population with a known link to the target population under the framework of a layered hidden Markov model. We apply the new methods to estimate the breeding population of an Ancient Murr...
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Full-text available
In capture–recapture studies, recycled individuals occur when individuals lose all of their tags and are recaptured as though they were new individuals. Typically, the effect of these recycled individuals is assumed negligible. Through a simulation‐based study of double‐tagging experiments, we examined the effect of recycled individuals on paramete...
Article
Habitat fragmentation is an increasingly serious issue affecting primates in most regions where they are found today. Populations of Lemur catta (ring-tailed lemur) in Madagascar's south-central region are increasingly restricted to small, isolated forest fragments, surrounded by grasslands or small-scale agriculture. Our aim was to evaluate the po...
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Full-text available
Monitoring the dynamics of the productivity of ocean water and how it affects fisheries is essential for management. It requires data on proper spatial and temporal scales, which can be provided by operational ocean colour satellites. However, accurate productivity data from ocean colour imagery is only possible with proper validation of, for insta...
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Batch marking provides an important and efficient way to estimate the survival probabilities and population sizes of wild animals. It is particularly useful when dealing with animals that are difficult to mark individually. For the first time, we provide the likelihood for extended batch-marking experiments. It is often the case that samples contai...
Article
We modelled how nestling growth rates of Cassin’s Auklet (Ptychoramphus aleuticus (Pallas, 1811)) varied with timing of peak copepod prey availability at two breeding colonies in British Columbia: on Triangle Island, in the California Current Ecosystem, and Frederick Island, in the Gulf of Alaska Ecosystem. We used time series of nestling growth ra...
Article
Background: Injection drug users (IDUs) are considered a hidden, hard to reach population that is difficult to measure. Multi-list recapture methods are commonly used to estimate IDU population sizes but do not allow inference on population dynamics. In Victoria, Canada, closed population capture–recapture methods have been used to estimate the abu...
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An increasing global demand for sea cucumbers has led to interest in benthic ranching of the California sea cucumber Parastichopus californicus beneath existing aquaculture sites in British Columbia, Canada, where high levels of total organic matter (TOM) are typical. The objective of the present study was to investigate movement of P. californicus...
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Peer review is seen as an important quality-assurance mechanism in both industrial development and the open-source software (OSS) community. The techniques for performing inspections have been well studied in industry; in OSS development, software peer reviews are not as well understood. To develop an empirical understanding of OSS peer review, we...
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Population size estimation is critical for planning public health programmes for injection drug users. Estimation is difficult, as these populations are considered 'hidden' or 'hard to reach'. The currently accepted population size estimate for greater Victoria, Canada is between 1,500 and 2,000 individuals, which is dated prior to the year 2000, a...
Article
Mark–recapture experiments involve capturing individuals from populations of interest, marking and releasing them at an initial sample time, and recapturing individuals from the same populations on subsequent occasions. The Jolly–Seber model is widely used in open-population models since it can estimate important parameters such as population size,...
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Full-text available
Little attention has been paid to the use of multi-sample batch-marking studies, as it is generally assumed that an individual's capture history is necessary for fully efficient estimates. However, recently, Huggins et al. (2010) present a pseudo-likelihood for a multi-sample batch-marking study where they used estimating equations to solve for sur...
Data
Figure S1. Boxplots of capture probability estimates () of 100 simulated datasets, for the Crosbie–Manley–Arnason–Schwarz (C: red), the likelihood (L: green), and the pseudo-likelihood (H: yellow; Huggins et al. 2010) when parameters values are N = 1000, and p = 0.2,0.5,0.8 for ϕ = 0.2 (top), and ϕ = 0.5 (middle), ϕ = 0.8 (bottom). Figure S2. Boxpl...
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Syphilis is a sexually transmitted disease caused by Treponema pallidum subsp. pallidum; it can be effectively treated with penicillin yet remains prevalent worldwide, due in part to the shortcomings of current diagnostic tests. Here we report the production of soluble recombinant versions of three novel diagnostic candidate proteins, Tp0326, Tp045...
Article
Systematic reviews and meta-analyses show that needle exchange programs reduce HIV and HCV transmission for injection drug users (IDUs) but far less is known about the injection practices of IDUs enrolled in these programs. This study adopts a mixed methods approach to quantify high-risk injection practice patterns among IDUs enrolled in a needle e...
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Full-text available
We used artificial eggs containing miniature temperature loggers to quantify nest attendance patterns by breeding Rhinoceros Auklets Cerorhinca monocerata over two seasons. The first year coincided with a strong El Niño event and low breeding success, while the second was one of La Niña conditions and high colony-wide productivity. Logger data reve...
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Full-text available
Mark-recapture experiments are performed to estimate population parameters such as survival probabilities. Animals are captured, tagged, released, and recaptured at subsequent time periods in order to obtain parameter information. The Jolly-Seber-Tag-Loss (JSTL) model (Cowen & Schwarz, 2006) requires some individuals to be double tagged in order to...
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Full-text available
Multistate mark-recapture models can be used to model migration through stratification of the study area into states (location). However, the incorporation of both tag loss and reporting rates is new to the multistate paradigm. We develop a migration model for fish that incorporates tag loss and reporting rates but has as its primary purpose the mo...
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Full-text available
The concept of risk dominates the HIV/AIDS literature pertaining to People Who Use Injection Drugs (PWUID). In contrast the associated concept of worry is infrequently applied, even though it can produce important perspectives of PWUID's lives. This study asked a sample (n = 105) of PWUID enrolled in a Victoria, British Columbia needle exchange pro...
Article
Comparative global proteome analyses were performed on Leptospira interrogans serovar Copenhageni grown under conventional in vitro conditions and those mimicking in vivo conditions (iron limitation and serum presence). Proteomic analyses were conducted using iTRAQ and LC-ESI-tandem mass spectrometry complemented with two-dimensional gel electropho...
Article
To sustain viable fish populations, protect stocks of wild salmon Oncorhynchus spp., and successfully manage the Pacific salmon fishery, all sources of fishing mortality need to be understood. The fishery targeting Chinook salmon O. tshawytscha is an important component of the commercial, recreational, and First Nations fisheries in British Columbi...
Article
Tag loss in mark-recapture experiments is a violation of one of the Jolly-Seber model assumptions. It causes bias in parameter estimates and has only been dealt with in an ad hoc manner. We develop methodology to estimate tag retention and abundance in double-tagging mark-recapture experiments. We apply this methodology to walleyes (Stizostedion vi...
Article
Radio tags, because of their high detectability, are often used in capture-recapture studies. A key assumption is that radio tags do not cease functioning during the study. Radio-tag failure before the end of a study can lead to underestimates of survival rates. We develop a model to incorporate secondary radio-tag failure data. This model was appl...
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Full-text available
We evaluated the causes and consequences of mate switching in crested auklets (Aethia cristatella). The crested auklet is a small seabird in which both sexes are similarly ornamented and contribute to parental care. We observed 29 pairs and found that 31% changed mates between breeding seasons. In a logistic regression analysis, we used absolute cr...
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To measure magnitude, type, and central tendency of astigmatism found in a county-wide population of Canadian preschool children (mean age, 48.1 months). Noncycloplegic autorefractive measures were taken in 1179 children attending a preschool health fair operated by their county board of health. Spherocylinder measures were transformed into three i...
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Full-text available
We studied parental provisioning and chick growth rates of Cassin's auklet Ptychoramphus aleuticus at Triangle Island, British Columbia, Canada, from 1996 to 1999. Auklet reproductive performance and ocean climate conditions during these years were highly variable, and reflected in the diet composition. Chick growth was maximal when the diet was pr...
Article
We used high-frequency surveillance radar as a non-intrusive method to census nocturnal burrow-nesting Cassin's Auklet (Ptychoramphus aleuticus) on the world's largest colony, Triangle Island, British Columbia. In the largest subcolony, West Bay, the radar unit was operated 2200-0510 h nightly from 30 Apr.-11 May 1996 during the onset of hatching....
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Thesis (Ph.D.)--Simon Fraser University, 2005. Includes bibliographical references.

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