Quantitative genetic variation in the fish, tilapia (Oreochromis mossambicus)

This study investigated the genetic variation of economic traits in seawater cage cultured O. mossambicus in Hawaii. A hierarchical experimental design was implemented consisting of 31 sires and 61 dams. Twenty-nine paternal half-sib families, 61 full-sib families, and 22 replicated families were analyzed. The body measurements of weight, total length, head size, and height size were recorded monthly from 1- to 5- months of age. At the end of the fifth month all fish were sacrificed and measured for the additional traits of drawnweight, intestinal length, and gill surface area. Males and females were distinguished in the 3- to 5- month old data. In spite of past evidence suggesting a depauperate gene pool for Q. mossambicus in Hawaii, the results in this study reveal genetic variation in the population. Significant differences among sires and among dams within sire were found in both males and females for weight at 4months of age and in males only at 5- months of age for weight, drawnweight, and total length. The estimated narrow-sense heritabilities derived from the sire component of variance for the above traits were in the intermediate range with values from 0.31 to 0.39. The genetic correlations between the male traits ranged from 0.87 to unity. These findings suggest that growth rate of O. mossambicus in Hawaii has the potential to be improved by genetic selection techniques.