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Harvie, C. J. and B. M. Jessop (1990). Evaluation of designs of periodic count surveys for the estimation of escapement at a fishway. North American Journal of Fisheries Management. 10:39-45.
Counts of the number of alewives Alosa pseudoharengus migrating through the fishway on the Gaspereau River, Nova Scotia, were used to evaluate the accuracy and precision of various sampling schemes for estimating the population mean (true mean count/sample unit (15 min)). High variability in counts within day and season required more intensive sampling than suggested by previous studies to estimate the population mean to within a given percent relative error. Stratification in some cases doubled or tripled the precision of the estimated mean relative to the mean obtained from simple random sampling, whereas systematic sampling produced no gain in precision. Stratification to reduce the number of sample units required for a given precision may reduce the power of a test to detect differences between annual estimates of population means, depending on their variances. The importance of these interrelated factors should be determined before a particular scheme and level of effort are chosen for sampling.
U.S. Department of the Interior |
U.S. Geological Survey
URL: http://www.umesc.usgs.gov/data_library/fisheries/fish_passage/harvie.html
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