Use of molecular tools for research and improvement of aquaculture stocks

Development of molecular genetic markers provides aquaculture with tools for a number of research and practical applications. Genetic marking of experimental groups allows their evalu- ation in the same rearing units, increasing statistical power within limited research infrastructure. Parentage can be inferred for individuals in mixed-progeny groups, quantifying the contributions of individual parents and supporting the estimation of sire and dam effects. Building upon parent- age assignment, walk-back selection entails retention of the best members of each family as broodstock for the next generation. Molecular markers can be used to detect the segregation of quantitative trait loci (QTL) and knowledge of such linkages can be used for marker-assisted selection. Gene expression profiling can identify genes affecting traits of interest, providing can- didates for QTL or functional analysis. Purposeful genetic marking can be used to identify pro- prietary stocks, marketed products, and fish out-planted or escaping into natural ecosystems. Although each application has been demonstrated, genetic markers are not routinely used in commercial aquaculture. The limited practical application can be explained by the limited devel- opment of broodstocks for most aquaculture species, the small size and limited scope of most aquaculture operations, and the costs of genetic screening