The development of breeding programmes in aquaculture has been slow. Some selection experiments were started as early as the 1920s to improve disease resistance and growth rates and the response was good. Later, no response was shown in selection experiments to improve the growth rate in common carp and tilapia. This lack of selection response become well known and was one of the reasons for the start of breeding programmes receiving little interest for many years in aquaculture. More recent results in Atlantic salmon, rainbow trout, coho salmon, channel catfish and tilapia have shown that there is a good possibility of obtaining large genetic gain from selection. Since fecundity is high in most species, inbreeding is a problem if pedigree is not kept. Because of high fecundity it is possible to draw as many samples as wanted from each family in order to test and record the different traits selected for. This makes it possible to apply challenge tests for disease resistance, utilize specialized equipment to measure flesh quality, etc., to select efficiently for these traits in a breeding programme. If body weight is the only trait selected for, individual selection is recommended. A simple procedure is to use many pairs of parents and limit the number of progenies from each pair in order to control inbreeding. If several traits are included in the breeding goal a combined individual and family selection is recommended.
