Douglas S. Robson

Allylglucosinolate and Herbivorous Caterpillars: A Contrast in Toxicity and Tolerance

Allylglucosinolate, found in many cruciferous plants, is acutely toxic to Papilio polyxenes larvae, which do not normally attack crucifers. By contrast, larval growth of Pieris rapae, a crucifer specialist, is not affected even by artificially high concentrations of allylglucosinolate. Larval growth of Spodoptera eridania, a generalist feeder, is inhibited by high but not by low concentrations of the compound.

Sample Size in Petersen Mark–Recapture Experiments

Abstract The efficient planning of a Petersen-type mark and recapture experiment requires some knowledge of the order of magnitude of the population size N. Sample sizes M and C of the mark and recapture samples, respectively, may then be ascertained on the basis of a guessed value of N to achieve any desired degree of accuracy with any specified degree of confidence. Restrictions on the sample sizes M and C are that MC must exceed 4 times the guessed value of N, and the total costs of M and C must be equal. Graphs and formulas are given defining sample size to attain preassigned levels of accuracy and precision of population estimation. A method of choosing sample sizes such that experimental costs are minimized is described.

Catch Curves and Mortality Rates

Abstract The assumptions necessary to obtain a valid estimate of survival rate from a single catch curve are discussed. An example of the best estimate of survival rate and its variance is worked out for the case that age is known exactly for the entire sample. A test for validity of the model is illustrated. Methods of estimating the survival rate are also given when some age groups are combined, when an age-length key is used, and when only a segment of the catch curve is usable. A table is provided to facilitate the estimation in this last case.

Applications of Multivariate Polykays to the Theory of Unbiased Ratio-Type Estimation

Abstract The multivariate polykays, or multipart k-statistics, are obtained as a slight extension of results given by Tukey [4] for the univariate polykays. The relationship between this system and the system of multivariate symmetric means is indicated and multiplication formulas are given. An application of these results to the construction of unbiased ratio-type estimators and variance estimates for finite populations is given as a further illustration of the usefulness of polykays.

Techniques for wildlife investigations : design and analysis of capture data

Statistical inference in experimentation use of preliminary survey data surveys of animal abundance comparative censuses manipulative experiments environmental assessment studies. Appendices: General variance component formula noncentral F-tables additional noncentral F-tables.

Catch Rate Estimation for Roving and Access Point Surveys

Abstract Optimal designs of recreational angler surveys may require complemented surveys, in which different contact methods are used to estimate effort and catch. All common methods of estimating catch involve on-site interviews that may either be based on access (complete trip) or roving (incomplete trip) interviews. In roving surveys, anglers to be interviewed on a given day are intercepted with a probability proportional to the length of their completed fishing trip, whereas in access surveys, anglers are intercepted as they leave the fishery and are intercepted with the same probability regardless of the length of their completed fishing trip. There are four complemented survey designs which use interviews at access points (mail–access, telephone–access, aerial–access, and roving–access); there are four corresponding designs which use roving interviews (mail–roving. telephone–roving, aerial–roving, and roving–roving). For all of these surveys, total catch is estimated as the product of total effort a...

CALCULATION OF CATCH RATE AND TOTAL CATCH IN ROVING SURVEYS OF ANGLERS

SUMMARY To estimate the total catch in a sport fishery sampled by a roving creel survey, we multiply an estimate of the total fishing effort by the estimated catch rate (i.e., catch per unit of fishing effort). While the statistical theory for estimating the fishing effort from instantaneous or progressive counts is well established, there is much confusion about the appropriate way to estimate the catch rate. Most studies have used the ratio of means or the mean of the ratios of individual catches and efforts. We analyzed the properties of these estimators of catch rate under the assumption that fishing is a stationary Poisson process. The ratio of means estimator has a finite second moment, while the mean ratio estimator has infinite variance. Simulation studies showed that the mean of ratios estimator tends to have high and unstable mean squared error relative to the ratio of means estimator and this is in accordance with empirical observations. We also studied the properties of the mean of ratios estimator when all interviews with people fishing for less than e minutes duration were disregarded for values of e up to 60 minutes. There was typically a marked reduction in mean squared error when the shorter trips were not included. We recommend that the mean of ratios estimator, with all trips less than 30 minutes disregarded, be used to estimate catch rate and hence total catch under the roving creel survey design. It has the correct expectation (at least approximately after the truncation) and almost always had smaller mean squared error than the ratio of means estimates in our simulations.

Age-specific dose-mortality effects of Beauveria bassiana (Deuteromycotina: Hyphomycetes) on the European corn borer, Ostrinia nubilalis (Lepidoptera: Pyralidae)

Abstract Three isolates of Beauveria bassiana were evaluated under laboratory conditions for pathogenicity against the European corn borer, Ostrinia nubilalis. Dose-mortality regressions and nonparametric statistical analyses revealed significant differences in pathogenicity between isolates and across O. nubilalis instars. First instars were found to be the most susceptible of the five larval stages. Little difference was noted for instars 2, 3, and 5 within any of the three B. bassiana isolates. Fourth instar larvae were found to be the most tolerant in all cases.

The Theoretical Basis of an Access Site Angler Survey Design

The theoretical basis is presented for a new design of angler surveys. The design was used in a survey to assess recreational fishing on New Yorks Great Lakes and tributaries. The large geographic area and budget constraints necessitated a survey design that could cover broad areas with the maximum efficiency of a limited number of survey agents. The model for the survey relates the amount of time that a survey agent has the angling partys car in view at an access site with the amount of time the party spent fishing. Geometric inclusion probability functions are developed and equations for estimating fishing effort are given. The special case when access sites are not limited to angler use (the case for many marinas) is also discussed and an estimator for fishing effort developed.

Independent stepwise residuals for testing homoscedasticity

Abstract Regression models which specify independent, homoscedastic and normally distributed errors may be analyzed in a stepwise manner to produce calculated residuals having this same property. If the nth residual is calculated as the deviation of the nth observation from its predicted value based on a least squares fit to only the first n observations then the resulting sequence of residuals, appropriately normalized, are not only mutually independent and homoscedastic but are also independent of all of the calculated regression functions. If error variance is a monotonic function of the mean then, under certain regularity conditions, the calculated stepwise residuals are likewise monotonically heteroscedastic. Simple linear regression with equally spaced values of the independent variable constitutes one such regular case, and a Monte Carlo study of the “peak-test” of homoscedasticity in this instance shows that for small samples the stepwise residuals are substantially more sensitive to monotonic het...