The aquaculture industry in Zambia has increasingly become critical for food, income and nutrition security. However, the industry still faces major constraints including high feed costs, insufficient quality seed and slow growth among the indigenous species. In response, the Zambian government prioritized to improve the genetics of the three spotted tilapia through the Genetic Improvement Program (GIP). The main objective of the GIP is to improve the growth performance of the species targeting harvest weight and survival as the key traits of interest.
Linear mixed models were fitted to estimate variance components and narrow-sense heritability for harvest weight and individual survival at harvest. The overall survival rate at harvest was 72.5% while heritability was 0.59 ± 0.06 for harvest weight and 0.11 ± 0.02 (observed scale) or 0.19 ± 0.04 (underlying scale given an) for individual survival at harvest. The heritability estimate for harvest weight could have inflated due to the absence of maternal half-sib structure to disentangle the environmental effects common to full-sibs (called c2) from the genetic effect. However, with a sufficiently large number (152) of families available post-harvest and a fairly high additive genetic variation, harvest weight will respond favorably to selection in the future. These results are comparable to other tilapia breeding programs and as such this work provides the basis for future assessments of selected generations for increased bodyweight at harvest for O. andersonii as part of the Genetic Improvement Program for the species.
Using three founding fish populations, a complete diallel cross (Table 1) was carried out as the first step to produce the synthetic base population. The base population consisted of full sib families produced in hapas and nursed separately prior to being tagged with Passive Integrated Transponder (PIT) tags. To assess performance, the fish were grown communally to harvest size in earthen ponds which are the most used culture environment for O. andersonii in Zambia.