Abstract

Genetic information from managed fish populations is often used to estimate genetic effective population size, N,. Managers must weigh the cost of genetic study as determined in part by sampling effort, against potential benefits that arc determined by the hypotheses that the data can address adequately (i.e. statistical power). This paper is a case study that examines statistical power to estimate Ne, in red drum (Sciaenops ocellatus) through the use of genetic markers. Extensive genetic information available for this species permitted comparison of three commonly used classes of genetic markers: (i) allozymes; (ii) mitochondrial (mt) DNA; and (iii) microsatellite DNA loci. Statistical power analysis indicated that all three classes of genetic markers can estimate small genetic effective population sizes (Ne < 100) with high accuracy and statistical confidence, given a large number of individuals sampled. As Ne increases above 500, statistical power and accuracy differ among markers: mtDNA performed best, followed by microsatellites, and then allozymes. Power is higher for mtDNA because the effective size of the mtDNA locus is one-quarter the effective size of diploid, nuclear loci (i.e., microsatellites and allozymes). For nuclear markers, increasing number of independent DNA microsatellite loci increases statistical power more effectively than increasing the number of allozyme loci. An indirect estimate of Ne from mtDNA restriction site data indicates that effective population size of red drum is sufficiently large to preclude critical losses of genetic diversity to drift despite recent declines in abundance.

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