Brian Gray, PhD
Brian Gray
Education and Certifications
Ph.D., Biostatistics, University of South Carolina, 2001
M.S., Biology, University of Kentucky, 1993
Diploma in Natural Resources, Lincoln University, 1982
B.Sc., Botany, University of Auckland, 1981
Science and Products
Filter Total Items: 48
Variance components estimation for continuous and discrete data, with emphasis on cross-classified sampling designs
Variance components may play multiple roles (cf. Cox and Solomon 2003). First, magnitudes and relative magnitudes of the variances of random factors may have important scientific and management value in their own right. For example, variation in levels of invasive vegetation among and within lakes may suggest causal agents that operate at both spatial scales – a finding that may be important for s
Authors
Brian R. Gray
Population assessment and potential functional roles of native mussels in the Upper Mississippi River
1. Despite a heightened global concern for native mussels, fundamental research on mussel ecology in large rivers is lacking. These gaps in knowledge about where mussels occur, and why, are limiting habitat restoration activities. 2. Large-scale systematic surveys for native mussels in three reaches of the Upper Mississippi River documented mussel communities composed of 16–23 species and ranging
Authors
Teresa J. Newton, Steven J. Zigler, James T. Rogala, Brian R. Gray, Mike Davis
Effects of injected methylmercury on the hatching of common loon (Gavia immer) eggs
To determine the level of in ovo methylmercury (MeHg) exposure that results in detrimental effects on fitness and survival of loon embryos and hatched chicks, we conducted a field study in which we injected eggs with various doses of MeHg on day 4 of incubation. Eggs were collected following about 23 days of natural incubation and artificially incubated to observe hatching. Reduced embryo survival
Authors
Kevin P. Kenow, Michael W. Meyer, Ronald Rossmann, Annette Gendron-Fitzpatrick, Brian R. Gray
Estimating site occupancy rates for aquatic plants using spatial sub-sampling designs when detection probabilities are less than one
Estimation of site occupancy rates when detection probabilities are <1 is well established in wildlife science. Data from multiple visits to a sample of sites are used to estimate detection probabilities and the proportion of sites occupied by focal species. In this article we describe how site occupancy methods can be applied to estimate occupancy rates of plants and other sessile organisms. We i
Authors
R. M. Nielson, B. R. Gray, L.L. McDonald, P.J. Heglund
Multinomial mixture model with heterogeneous classification probabilities
Royle and Link (Ecology 86(9):2505–2512, 2005) proposed an analytical method that allowed estimation of multinomial distribution parameters and classification probabilities from categorical data measured with error. While useful, we demonstrate algebraically and by simulations that this method yields biased multinomial parameter estimates when the probabilities of correct category classifications
Authors
M.D. Holland, Brian R. Gray
An evaluation of the Bayesian approach to fitting the N-mixture model for use with pseudo-replicated count data
The N-mixture model proposed by Royle in 2004 may be used to approximate the abundance and detection probability of animal species in a given region. In 2006, Royle and Dorazio discussed the advantages of using a Bayesian approach in modelling animal abundance and occurrence using a hierarchical N-mixture model. N-mixture models assume replication on sampling sites, an assumption that may be viola
Authors
S.G. Toribo, B. R. Gray, S. Liang
Evaluation of single and two-stage adaptive sampling designs for estimation of density and abundance of freshwater mussels in a large river
Reliable estimates of abundance are needed to assess consequences of proposed habitat restoration and enhancement projects on freshwater mussels in the Upper Mississippi River (UMR). Although there is general guidance on sampling techniques for population assessment of freshwater mussels, the actual performance of sampling designs can depend critically on the population density and spatial distrib
Authors
D. R. Smith, J. T. Rogala, B. R. Gray, S. J. Zigler, T.J. Newton
Cumulative effects of restoration efforts on ecological characteristics of an open water area within the Upper Mississippi River
Ecological restoration efforts in large rivers generally aim to ameliorate ecological effects associated with large-scale modification of those rivers. This study examined whether the effects of restoration efforts-specifically those of island construction-within a largely open water restoration area of the Upper Mississippi River (UMR) might be seen at the spatial scale of that 3476ha area. The c
Authors
B. R. Gray, W. Shi, J.N. Houser, J. T. Rogala, Z. Guan, J. L. Cochran-Biederman
Polychlorinated biphenyls, dioxins, furans, and organochlorine pesticides in spotted sandpiper eggs from the upper Hudson River basin, New York
In 2004, spotted sandpipers (Actitis macularia) were studied on the Hudson River near Fort Edward south to New Baltimore, NY and on two river drainages that flow into the Hudson River. Concentrations of 28 organochlorine pesticides, 160 polychlorinated biphenyl (PCB) congeners, and 17 dioxin and furan (PCDD-F) congeners were quantified in eggs collected on and off the Hudson River. The pattern of
Authors
Thomas W. Custer, Christine M. Custer, Brian R. Gray
Effects of egg order on organic and inorganic element concentrations and egg characteristics in tree swallows, tachycineta bicolor
The laying order of tree swallow eggs was identified from the Housatonic River, Berkshire County, Massachusetts, USA, and eggs were chemically analyzed individually to document possible effects of laying order on organic contaminant and inorganic element concentrations. Effects of laying order on other parameters such as egg weight, size, and lipid and moisture content also were assessed. Some eff
Authors
Christine M. Custer, Brian R. Gray, Thomas W. Custer
A finite population Bayes procedure for censored categorical abundance data
No abstract available.
Authors
Mark D. Holland, Glen Meeden, Brian R. Gray
Effect of imperfect detectability on adaptive and conventional sampling: Simulated sampling of freshwater mussels in the upper Mississippi River
Adaptive sampling designs are recommended where, as is typical with freshwater mussels, the outcome of interest is rare and clustered. However, the performance of adaptive designs has not been investigated when outcomes are not only rare and clustered but also imperfectly detected. We address this combination of challenges using data simulated to mimic properties of freshwater mussels from a reach
Authors
D. R. Smith, B. R. Gray, T.J. Newton, D. Nichols
Science and Products
Filter Total Items: 48
Variance components estimation for continuous and discrete data, with emphasis on cross-classified sampling designs
Variance components may play multiple roles (cf. Cox and Solomon 2003). First, magnitudes and relative magnitudes of the variances of random factors may have important scientific and management value in their own right. For example, variation in levels of invasive vegetation among and within lakes may suggest causal agents that operate at both spatial scales – a finding that may be important for s
Authors
Brian R. Gray
Population assessment and potential functional roles of native mussels in the Upper Mississippi River
1. Despite a heightened global concern for native mussels, fundamental research on mussel ecology in large rivers is lacking. These gaps in knowledge about where mussels occur, and why, are limiting habitat restoration activities. 2. Large-scale systematic surveys for native mussels in three reaches of the Upper Mississippi River documented mussel communities composed of 16–23 species and ranging
Authors
Teresa J. Newton, Steven J. Zigler, James T. Rogala, Brian R. Gray, Mike Davis
Effects of injected methylmercury on the hatching of common loon (Gavia immer) eggs
To determine the level of in ovo methylmercury (MeHg) exposure that results in detrimental effects on fitness and survival of loon embryos and hatched chicks, we conducted a field study in which we injected eggs with various doses of MeHg on day 4 of incubation. Eggs were collected following about 23 days of natural incubation and artificially incubated to observe hatching. Reduced embryo survival
Authors
Kevin P. Kenow, Michael W. Meyer, Ronald Rossmann, Annette Gendron-Fitzpatrick, Brian R. Gray
Estimating site occupancy rates for aquatic plants using spatial sub-sampling designs when detection probabilities are less than one
Estimation of site occupancy rates when detection probabilities are <1 is well established in wildlife science. Data from multiple visits to a sample of sites are used to estimate detection probabilities and the proportion of sites occupied by focal species. In this article we describe how site occupancy methods can be applied to estimate occupancy rates of plants and other sessile organisms. We i
Authors
R. M. Nielson, B. R. Gray, L.L. McDonald, P.J. Heglund
Multinomial mixture model with heterogeneous classification probabilities
Royle and Link (Ecology 86(9):2505–2512, 2005) proposed an analytical method that allowed estimation of multinomial distribution parameters and classification probabilities from categorical data measured with error. While useful, we demonstrate algebraically and by simulations that this method yields biased multinomial parameter estimates when the probabilities of correct category classifications
Authors
M.D. Holland, Brian R. Gray
An evaluation of the Bayesian approach to fitting the N-mixture model for use with pseudo-replicated count data
The N-mixture model proposed by Royle in 2004 may be used to approximate the abundance and detection probability of animal species in a given region. In 2006, Royle and Dorazio discussed the advantages of using a Bayesian approach in modelling animal abundance and occurrence using a hierarchical N-mixture model. N-mixture models assume replication on sampling sites, an assumption that may be viola
Authors
S.G. Toribo, B. R. Gray, S. Liang
Evaluation of single and two-stage adaptive sampling designs for estimation of density and abundance of freshwater mussels in a large river
Reliable estimates of abundance are needed to assess consequences of proposed habitat restoration and enhancement projects on freshwater mussels in the Upper Mississippi River (UMR). Although there is general guidance on sampling techniques for population assessment of freshwater mussels, the actual performance of sampling designs can depend critically on the population density and spatial distrib
Authors
D. R. Smith, J. T. Rogala, B. R. Gray, S. J. Zigler, T.J. Newton
Cumulative effects of restoration efforts on ecological characteristics of an open water area within the Upper Mississippi River
Ecological restoration efforts in large rivers generally aim to ameliorate ecological effects associated with large-scale modification of those rivers. This study examined whether the effects of restoration efforts-specifically those of island construction-within a largely open water restoration area of the Upper Mississippi River (UMR) might be seen at the spatial scale of that 3476ha area. The c
Authors
B. R. Gray, W. Shi, J.N. Houser, J. T. Rogala, Z. Guan, J. L. Cochran-Biederman
Polychlorinated biphenyls, dioxins, furans, and organochlorine pesticides in spotted sandpiper eggs from the upper Hudson River basin, New York
In 2004, spotted sandpipers (Actitis macularia) were studied on the Hudson River near Fort Edward south to New Baltimore, NY and on two river drainages that flow into the Hudson River. Concentrations of 28 organochlorine pesticides, 160 polychlorinated biphenyl (PCB) congeners, and 17 dioxin and furan (PCDD-F) congeners were quantified in eggs collected on and off the Hudson River. The pattern of
Authors
Thomas W. Custer, Christine M. Custer, Brian R. Gray
Effects of egg order on organic and inorganic element concentrations and egg characteristics in tree swallows, tachycineta bicolor
The laying order of tree swallow eggs was identified from the Housatonic River, Berkshire County, Massachusetts, USA, and eggs were chemically analyzed individually to document possible effects of laying order on organic contaminant and inorganic element concentrations. Effects of laying order on other parameters such as egg weight, size, and lipid and moisture content also were assessed. Some eff
Authors
Christine M. Custer, Brian R. Gray, Thomas W. Custer
A finite population Bayes procedure for censored categorical abundance data
No abstract available.
Authors
Mark D. Holland, Glen Meeden, Brian R. Gray
Effect of imperfect detectability on adaptive and conventional sampling: Simulated sampling of freshwater mussels in the upper Mississippi River
Adaptive sampling designs are recommended where, as is typical with freshwater mussels, the outcome of interest is rare and clustered. However, the performance of adaptive designs has not been investigated when outcomes are not only rare and clustered but also imperfectly detected. We address this combination of challenges using data simulated to mimic properties of freshwater mussels from a reach
Authors
D. R. Smith, B. R. Gray, T.J. Newton, D. Nichols