Genetics, Vol. 173, 2063-2072, August 2006, Copyright © 2006
doi:10.1534/genetics.106.056424

Simultaneous Estimation of Mixing Rates and Genetic Drift Under Successive Sampling of Genetic Markers With Application to the Mud Crab (Scylla paramamosain) in Japan

Toshihide Kitakado*,1, Shuichi Kitada*, Yasuhiro Obata{dagger} and Hirohisa Kishino{ddagger}

* Faculty of Marine Science, Tokyo University of Marine Science and Technology, Minato, Tokyo 108-8477, Japan, {dagger} Tamano Station, National Center for Stock Enhancement, Fisheries Research Agency, Chikko, Tamano, Okayama 706-0002, Japan and {ddagger} Graduate School of Agriculture and Life Sciences, University of Tokyo, Bunkyo, Tokyo 113-8657, Japan

1 Corresponding author: Tokyo University of Marine Science and Technology, 5-7, Konan 4, Minato-ku, Tokyo, 108-8477, Japan.
E-mail: kitakado{at}s.kaiyodai.ac.jp

In stock enhancement programs, it is important to assess mixing rates of released individuals in stocks. For this purpose, genetic stock identification has been applied. The allele frequencies in a composite population are expressed as a mixture of the allele frequencies in the natural and released populations. The estimation of mixing rates is possible, under successive sampling from the composite population, on the basis of temporal changes in allele frequencies. The allele frequencies in the natural population may be estimated from those of the composite population in the preceding year. However, it should be noted that these frequencies can vary between generations due to genetic drift. In this article, we develop a new method for simultaneous estimation of mixing rates and genetic drift in a stock enhancement program. Numerical simulation shows that our procedure estimates the mixing rate with little bias. Although the genetic drift is underestimated when the amount of information is small, reduction of the bias is possible by analyzing multiple unlinked loci. The method was applied to real data on mud crab stocking, and the result showed a yearly variation in the mixing rate.