This approach is not only useful in itself in the sense that it enables a logical treatment of the subject matter, but it is also helpful in the identification of areas in which knowledge or its application are deficient, and that should therefore become the
target of research, development and technology transfer. As the genetic improvement programs unfold, limitations and areas where there is room for refinements are identified. These, then become focused research areas, the results from which feed back into the program making it gradually more effective.
At present, especially in newly initiated genetic improvement programs, growth is likely to continue to be the main focus of selection. This is justified because of the great economic importance of the trait in the production system given the very high reproductive rate of fish. Most developing countries completely lack improved strains, so initially, even despite possible evidence about G x E, a single program will have to service a range of production environments. Later, as the program progresses, gets consolidated, and production systems get better defined, resources permitting, specialized programs servicing specific production systems may be developed. With the development of more sophisticated markets, either domestic or export, the need to select for fillet yield and flesh quality traits may emerge. This will add complexity to the programs and inevitable fully pedigreed populations and BLUP (Best Linear Unbiased Prediction) evaluations for the estimation of genetic merit of such traits will have to be conducted. Selection for less conventional traits, such as sensitivity to thermal treatments with the purpose of producing all male progeny, may have to be integrated as well to increase the efficiency of some production systems. Selection for disease resistance has not emerged as a priority in tilapia, but it may in the future as production systems intensify. The classic selective breeding technology based on quantitative genetics can serve selection programs for growth rate and survival well, but for the more difficult to measure traits such as carcase and flesh quality,sensitivity to thermal treatment and disease resistance, molecular techniques would be very valuable if they enable selection on markers or directly on the genes affecting the trait. Our perception is that in the foreseeable future simple programs totally based on quantitative genetics will co-exist with much more sophisticated ones using quantitative genetics jointly with state of the art molecular genetics techniques, each program effectively servicing a specific set of production, economic and social conditions.