<b>Respuesta generacional al mejoramiento genético por peso en familias de tilapia nilótica GIFT (<i>Oreochromis niloticus</i>) bajo un esquema de selección masal y apareamiento rotativo</b>

Studies on tilapia indicate that body weight has moderate to high heritability. When applied to selective breeding programs focused on weight improvement in this species, these findings have enabled evaluation of growth performance and generational behavior using the individual multi-stage selection method described in the GIFT Technology Manual (WorldFish Center, 2004). Weight values remained within a central range due to the staggered incorporation of family groups, the mass selection process for the weight trait, the effective population size of each family group, and the implementation of rotational crossing, which allowed for variability and the gradual improvement of quantitative traits around the population mean. The average weights of successive generations of family groups, along with their growth patterns, showed a consistent increase from one generation to the next, reaching a weight range of 500-700 g. A broodstock weight classification is proposed: females were grouped into three categories: High (600 g), Medium (400–500 g), and Low (300 g). Males were classified as High (900–1000 g) and Medium (700 g). The objective of this study is to determine the weight performance of generational family groups of GIFT Nile tilapia (Oreochromis niloticus) resulting from selective improvement, and to apply a classification method for families based on weight and sex as a tool for implementing inter-family mating strategies.