Significance of genetic management of broodstock in aquaculture using DNA markers

Abstract

Large numbers of seed fish have been produced in both public and private hatcheries for stock enhancement programs and aquaculture of red sea bream, Pagrus major for several decades in Japan. Production increased to about 120 million seed fish in 1997. Artificial propagation using a small number of parental fish in hatcheries may result loss of genetic variation and increase of inbreeding that may induce negative elects on the genetic diversity and fitness of both hatchery stocks and wild populations. Since microsatellite loci provide co-dominant DNA markers that are usually inherited in a Mendelian fashion and are hypervariabie compared with conventional protein markers, microsatelllite polymorphism is expected to be an effective tool for studies on the genetic divergence of wild populations as well as for the broodstock management in aquaculture. In this report, I review the researches on the genetic analysis of wild population and brood stock in red sea bream (Pagrus major) in Japan. The importance of population analysis with help of hypervariabie DNA markers is emphasized in relation to the estimation of effective population sizes (Ne) and inbreeding coefficients (F) for the broodstock and seed fish. The paper also consideres procedures for managing and conserving the genetic diversity of the broodstocks and wild populations of red sea bream. © 2002, The Japanese Society of Fisheries Science. All rights reserved.