Cavell Brownie

Design and analysis methods for fish survival experiments based on release-recapture

Design and analysis methods for fish survival experiments based on release-recapture / , Design and analysis methods for fish survival experiments based on release-recapture / , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Bootstrap Methods for Testing Homogeneity of Variances

This article describes the use of bootstrap methods for the problem of testing homogeneity of variances when means are not assumed equal or known. The methods are new in this context and allow the use of normal-theory test statistics such as F = s 2 1/s 2 2 without the normality assumption that is crucial for validity of critical values obtained from the F distribution. Both asymptotic analysis and Monte Carlo sampling show that the new resampling procedures compare favorably with older methods in terms of test validity and power.

Constant parameter capture-recapture models

Jolly (1982, Biometrics 38, 301-321) presented modifications of the Jolly-Seber model for capture-recapture data, which assume constant survival and/or capture rates. Where appropriate, because of the reduced number of parameters, these models lead to more efficient estimators than the Jolly-Seber model. The tests to compare models given by Jolly do not make complete use of the data, and we present here the appropriate modifications, and also indicate how to carry out goodness-of-fit tests which utilize individual capture history information. We also describe analogous models for the case where young and adult animals are tagged. The availability of computer programs to perform the analysis is noted, and examples are given using output from these programs.

Comparing Variances and Other Measures of Dispersion

Testing hypotheses about variance parameters arises in contexts where uniformity is important and also in relation to checking assumptions as a preliminary to analysis of variance (ANOVA), dose-response modeling, discriminant analysis and so forth. In contrast to procedures for tests on means, tests for variances derived assuming normality of the parent populations are highly nonrobust to nonnormality. Procedures that aim to achieve robustness follow three types of strategies: (1) adjusting a normal-theory test procedure using an estimate of kurtosis, (2) carrying out an ANOVA on a spread variable computed for each observation and (3) using resampling of residuals to determine p values for a given statistic. We review these three approaches, comparing properties of procedures both in terms of the theoretical basis and by presenting examples. Equality of variances is first considered in the two-sample problem followed by the k-sample problem (one-way design).

Role of Visual Contrast in the Alighting Behavior of Harmonia axyridis (Coleoptera: Coccinellidae) at Overwintering Sites

Abstract The multicolored Asian lady beetle Harmonia axyridis (Pallas) is often a pest during autumn, when large numbers take flight and subsequently land on and enter buildings. Open field experiments were conducted during the autumn flight to examine the role of linear contrast in visually attracting beetles. White targets printed with 61 by 15-cm stripes that varied in orientation and degree of contrast were covered in insect adhesive, attached to a white background panel, and erected in sites known to be attractive to flying beetles. Flights occurred when temperatures rose above 21°C. Diurnally, peak flight occurred between 1400 and 1600 hours but shifted progressively earlier within that framework as the flight season advanced. Beetles significantly chose targets with high contrast, black stripes; the number of beetles landing on all other contrast levels did not differ significantly from controls. Vertically positioned stripes attracted more beetles than horizontal ones, but not significantly. The effects of high contrast were absolute rather than relative. The number of beetles landing on targets with 50% contrast stripes did not increase when these were the highest contrast targets available. Results suggest that visual intensity contrast is key to understanding the behavior of H. axyridis in autumn and call into question some commonly accepted ideas regarding choice of overwintering sites. First, during migratory flight, H. axyridis is not visually attracted to the color white per se, and second, it is unlikely that, during flight, pheromones are involved in beetle orientation.

Genetics of sex pheromone blend differences between Heliothis virescens and Heliothis subflexa: a chromosome mapping approach.

Males of the noctuid moths, Heliothis virescens and H. subflexa locate mates based on species‐specific responses to female‐emitted pheromones that are composed of distinct blends of volatile compounds. We conducted genetic crosses between these two species and used AFLP marker‐based mapping of backcross families (H. subflexa direction) to determine which of the 30 autosomes in these moths contained quantitative trait loci (QTL) controlling the proportion of specific chemical components in the pheromone blends. Presence/absence of single H. virescens chromosomes accounted for 7–34% of the phenotypic variation among backcross females in seven pheromone components. For a set of three similar 16‐carbon acetates, two H. virescens chromosomes interacted in determining their relative amounts within the pheromone gland and together accounted for 53% of the phenotypic variance. Our results are discussed relative to theories about population genetic processes and biochemical mechanisms involved in the evolution of new sexual communication systems.

Long-Term Effects of Changing Land Use Practices on Surface Water Quality in a Coastal River and Lagoonal Estuary

The watershed of the Neuse River, a major tributary of the largest lagoonal estuary on the U.S. mainland, has sustained rapid growth of human and swine populations. This study integrated a decade of available land cover and water quality data to examine relationships between land use changes and surface water quality. Geographic Information Systems (GIS) analysis was used to characterize 26 subbasins throughout the watershed for changes in land use during 1992–2001, considering urban, agricultural (cropland, animal as pasture, and densities of confined animal feed operations [CAFOs]), forested, grassland, and wetland categories and numbers of wastewater treatment plants (WWTPs). GIS was also used together with longitudinal regression analysis to identify specific land use characteristics that influenced surface water quality. Total phosphorus concentrations were significantly higher during summer in subbasins with high densities of WWTPs and CAFOs. Nitrate was significantly higher during winter in subbasins with high numbers of WWTPs, and organic nitrogen was higher in subbasins with higher agricultural coverage, especially with high coverage of pastures fertilized with animal manure. Ammonium concentrations were elevated after high precipitation. Overall, wastewater discharges in the upper, increasingly urbanized Neuse basin and intensive swine agriculture in the lower basin have been the highest contributors of nitrogen and phosphorus to receiving surface waters. Although nonpoint sources have been emphasized in the eutrophication of rivers and estuaries such as the Neuse, point sources continue to be major nutrient contributors in watersheds sustaining increasing human population growth. The described correlation and regression analyses represent a rapid, reliable method to relate land use patterns to water quality, and they can be adapted to watersheds in any region.

Effects of Violation of Assumptions for Survival Analysis Methods in Radiotelemetry Studies

Two main methods of estimating survival from radiotelemetry studies are the Trent and Rongstad approach and the Kaplan-Meier approach. Although these 2 methods often are applied, the effects of violation of assumptions have not been completely studied. We present a very brief evaluation of all assumptions and their violation. We also evaluated the assumption of equal censoring rates for live and dead animals by simulation and found that large biases can result if it is violated. For the Trent-Rongstad method where there is an additional assumption of constant survival rates over time, our simulations showed that violation of this assumption caused the largest bias with an early drop in survival rate as compared to other alternatives.

Tag Return Models Allowing for Harvest and Catch and Release: Evidence of Environmental and Management Impacts on Striped Bass Fishing and Natural Mortality Rates

Abstract Catch-and-release fisheries have become very important in the management of overexploited recreational fish stocks. Tag return studies, where the tag is removed regardless of fish disposition, have been used to assess the effectiveness of restoration efforts for these fisheries. We extend the instantaneous rate formulation of tag return models to allow for catch and release as well as harvest. The key point of our methods is that, given an estimate of the tag reporting rate, the fishing mortality rate (F) is separated into two components: the mortality on harvested fish and the “mortality” on tags (because the tags are removed) of fish released alive. The total fishing mortality rate for untagged fish is the sum of the Fs due to harvest and hooking mortality suffered by fish released alive. Natural mortality rates can also be estimated. Both age-independent models and age-dependent models are constructed, and the age-dependent models are illustrated by application to data from a study of striped ...

EFFECT OF PBAN ON PHEROMONE PRODUCTION BY MATED Heliothis virescens AND Heliothis subflexa FEMALES

Mated female Heliothis virescens and H. subflexa were induced to produce sex pheromone during the photophase by injection of pheromone biosynthesis activating neuropeptide (PBAN). When injected with 1 pmol Hez-PBAN, the total amount of pheromone that could be extracted from glands of mated females during the photophase was similar to that extracted from virgin females in the scotophase. The PBAN-induced profile of pheromone components was compared between mated, PBAN-injected females and virgin females during spring and fall. Virgin females exhibited some differences in the relative composition of the pheromone blend between spring and fall, but no such temporal differences were detected in PBAN-injected, mated females. Because the temporal variation in pheromone blend composition was greater for virgin females than for PBAN-injected females, PBAN can be used to determine a female’s native pheromone phenotype. This procedure has the advantages that pheromone glands can be extracted during the photophase, from mated females that have already oviposited.